OzVMX Forum
Clubroom => Tech Talk => Topic started by: Ji Gantor on April 22, 2010, 11:29:27 pm
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When dealing with old bikes you will eventually come across a crack in the chassis or a broken bracket.
There has been a lot of words written about this topic on this forum but bike owners and restorers are still confused.
All agree that a repair is required.
I have seen lots of repairs and some frankly make me embarrassed to be part of the VMX crowd.
I am not saying for one instant that I am an expert, in fact I consider myself a white belt on the subject but some people should not do work they have no idea about, after all some repairs are just dangerous for anyone that rides that bike. So with that said lets explore how it can be done, keeping the structural integrity of the frame in tack while maintaining the original look.
Attached is a typical seat bracket that over 30 years has become cracked in a few places. The metal would be mild steel fixed to a chrome molly tube frame.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame1a.jpg)
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Start by wire brushing all the loose paint and rust off.
This will give a better idea of what is wrong and clean the surface ready for welding.
Take a small hammer and a dolly and tap the bracket back into its original shape.
Take your time with this as it will pay off down the track.
Once done fit the seat and see if everything lines up.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame4a.jpg)
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TIG welding is the best method in my opinion.
Use an appropriate filler rod and weld the cracks up.
Seeing how this metal is mild steel and the repair is so far away from the chrome molly tubes there is no need to post heat. If you feel that post heat should be done to remove stresses then that is great, it will not harm the frame if done right.
After the welding is finished sand not grind the bead flat and make the affected area look like new.
Take your time with this stage and the repair will hardly be seen.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame2a.jpg)
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You will have to sand both sides some times but it will be worth it in the end.
TIG welding allows you to lay the filler rod right where it is needed and gives you the time to get the job done right. It evenly heats the plates even though we are just welding not much more than a tack length, while still penetrating the metal.
This will look fantastic once it is bead blasted and powder coated not to mention strong.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame3a.jpg)
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Another typical bracket that gets cracked or torn off completely is the side number plate bracket.
These get treated pretty mean when the bike is crashed.
Our subject is cracked in two places and will need to be welded up.
This metal would be mild steel but this time the HAZ (heat affected zone) is close to the chrome molly tube.
The HAZ extends past the weld about 25 to 50mm and can be easely seen after welding.
If the HAZ extends to the tube post heating will be required.
Again wire brush the area and tap the bracket back into alignment.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame5a.jpg)
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TIG weld the crack and make sure there is plenty of filler at the end so the crack does not start again next time the bike is dropped.
This extra filler makes sure there is not a V left behind.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame6a.jpg)
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After the welding is done we can sand down the bead and make it all look great again.
Some resorters feel that a 30 year old frame is dangerous and should not be used and so they pay $10k or so for a replica frame and swingarm.
This is fine, each to their own, honestly I can not see how you can call yourself a restorer when you have started with all new parts. What did they restore? They should call themselves Bike Assemblers. If you are conserned that your frame may have unseen faults you can have it ultrasounded. This will reveal any potential problems for a fraction of the cost of a replica frame. If you feel your welding is not up to par get a boiler maker to weld up any known cracks, this to will not cost as much as you think and you will have peace of mind and a really good looking frame.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame7a.jpg)
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Hi Ji ,Do you think it be ok to mig weld a crack ,half way threw on front tube just above where both downtubes meet below side panel on bultaco frame? dont worry i wont hold you too it just your opinion would be helpful cheers
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Hi Huskibul,
Can you please upload an image of the affected area.
Is the person that is going to do the repair a competent MIG welder?
If so he will know what to do.
If it is a mate that has a MIG that only uses it now and then I would say don't.
Wire brush or sand blast the damaged area and do all the panel beating as required, then take the frame to a welding works and get a quote. It will only cost $50.00 and ask them to TIG weld it.
You will be surprised at the result.
Again what price would you pay to make sure when you land your bike over a big jump that you won't end up in the dirt because of a weld failure. We pay $200.00 for chest protectors and $700.00 for a Leatt why not shell out $50.00 for piece of mind.
Ji
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Just in case bike owners and restorers think that only these old chrome molly tube frames crack, think again.
The modern cast aluminium frames crack more often and are harder to repair. I am talking about bikes that are only a few years old. The disadvantage with tube frame is that it flexes, this deflection of the tubes ads say 5% to the shock absorption, while the cast alloy frames are very stiff. This stiffness allows the suspension and steering to do their jobs consistently, but think of a MX track like an earth quake. To survive the frame needs to be flexible or it will crack.
Some modern road bike frames crack the first time it jumps a kerb and the repair costs so much the owner is advised to sell the bike.
Ji
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Thanks Ji ,he's a ex fitter come boiler and he's already seen it, i will just get it done and keep my eye on it,thanks for the concern .as for the picture i haven't advanced(computer wise) that far yet, it,s a very fine crack running half way threw inside of downtube, should be fine ,i suppose it would be a worry if it was front downtube;)
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There are a few problems when MIG welding up chrome molly tubes.
First and most important is the filler rod. If you have a mate with a MIG he will most likely have mild steel wire on the spool. A spool of MIG wire costs about $100.00 and takes 10 minutes to change out. The mild steel wire will make the weld but is not the right metal for the job. A chrome molly TIG filler rod on the other hand costs $0.50 .
On small cracks that are only as long as a tack weld MIG in my experience is to quick and in the hands of the non-expert produce cold rope like weld beads. With TIG you increase the current or heat slowly via the foot pedal until the puddle is formed and then you add filler. This gives your eyes enough time to adjust to the arc and position the torch and filler.
Chrome molly is effected by heat, whether brazing or welding there will be a HAZ.
This HAZ can reduce the strength to only 40% of the tubes original load carrying capacity.
The HAZ needs to be post heat treated to retain strength and avoid brittleness.
In a frame making factory the frames after welding are placed into an oven and taken up to a set temp and then the heat is reduced over a long time.
Ji
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how dpo you post heat after welding now ?
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Gas
Ji
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Ji thats getting a little over my head but maybe i,d be better chasing the chrome moly rod/tig job now you put it that way?,i dont know about the post heating would any bloke with a tig know that ???or what would i tell him? :-\cheers
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Hi Huskibul,
Only if the fellow understands CrMo.
It is not complicated.
GMC does it all the time and so does any roll cage manufacturer.
Ji
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After the welding is done we can sand down the bead and make it all look great again.
Some resorters feel that a 30 year old frame is dangerous and should not be used and so they pay $10k or so for a replica frame and swingarm.
This is fine, each to their own, honestly I can not see how you can call yourself a restorer when you have started with all new parts. What did they restore? They should call themselves Bike Assemblers. If you are conserned that your frame may have unseen faults you can have it ultrasounded. This will reveal any potential problems for a fraction of the cost of a replica frame. If you feel your welding is not up to par get a boiler maker to weld up any known cracks, this to will not cost as much as you think and you will have peace of mind and a really good looking frame.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Frame7a.jpg)
Not exactly ultrasounded, a magnetic particle test is the best Non Desructive Testing (NDT) technique to disclose surface breaking and some sub surface cracks in most cases. Radiography is the ultimate, and would take quite a few shots to examine the entire frame, however, concentrating on the high stress areas such as the major gussets and load bearing tube connections will tell you what you need to know. I have some interesting test photos from the evaluation of a YZ 250 frame which demonstrates the effectiveness of each method. I will post some photos up when I get back to work if you like. Ultrasonic testing requires a very sophisticated immersion test station or water/couplant path transducers to cover the complexity of a bike frame, contact transducers require intimate coupling with the test surface to to be effective. Because of the multiple tube diameters and variation in geometry, you would wind up spending an exorbidant amount of time calibrating and testing then recal and test for each section you are inspecting. Stress relieving the entire frame after major repair is the way to go, this is achieved by annealing the frame in a vacuum furnace then restoring the temper to original specs in the same fashion. The frame would be as good as new following this process ;)
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Hi Rocketfrog,
Yes please, I would love to see the test images.
Ji
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Ji thats getting a little over my head but maybe i,d be better chasing the chrome moly rod/tig job now you put it that way?,i dont know about the post heating would any bloke with a tig know that ???or what would i tell him? :-\cheers
It's really simple the slower and more time taken to heat up and cool the area of the weld (pre-post heat) the more ductile the repair will be. Pre heating can be cheap spotlights on a large frame, propane torch waved over the area, post heating can be wrapping in fire blankets and leaving the spot lights on. An example is a submarine, when welded the whole hull is heated (to 80-90 deg C maybe higher) by DC curent for a month or so.
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Attached is an image of the TIG filler rods I carry.
From top to bottom,
Stainless Steel ER316L 1.6mm dia 1 meter long ($0.50),
Chrome moly ER80S-B2 1.6mm dia 1 meter long ($0.75),
Aluminium ER5356 1.6 and 2.4mm dia 1 meter long ($0.50),
Mild Steel S60 1.6mm dia ($0.50) 1 meter long and
Titanium Ti-Al6-V4 grade 5 1.6mm dia 460mm long ($1.75).
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Filler1a.jpg)
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I just received some Titanium grade 5 sheet.
Grade 5 is structural grade.
The sheet is 1.6mm thick.
Titanium has its base in aluminium but with added carbon like steel.
It has the strength of steel but a little less weight.
Magnets don't stick to it.
When welding it you set the machine up as if you are welding steel.
Ti is like stainless steel when it comes to oxygen shielding. All heated surfaces need to be argon gas shielded. The failure test is visual, post welding if the bead is silver or straw brown it is okay any other colour and the bead is contaminated.
This is a very basic run down on Ti.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Titanium1a.jpg)
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Titanium can be welded to titanium. It is difficult to weld it to aluminium but can be done, it can not be welded to steel.
The advantages are strong, light and does not rust.
Those BSA all titanium frames must have been terrible to weld in the sixties.
If you screw up a weld the Ti is ruined and must be replaced.
Once heated without proper shielding the Ti is cactused.
Ji
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Attached are some titanium foot pegs that are on the market for sale.
These pegs have been welded not CNC machined.
The blue colour is clearly seen.
So is the light brown colour.
I would be very interested in finding out how they welded these units.
I did not take this image.
It is from Geoff Ballard's catalogue.
If anyone is offended by its use here I will remove it on request.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Footpegs1a.jpg)
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Attached is an image of a flexible enclosure filled with argon gas ready to weld titanium.
There are other methods but this is the best way to ensure no contamination.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Titanium_enclosure1.jpg)
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From memory the BSA frames were done in vacuum chamber, problem was the frame was not able to be fixed at a gp because of this. Didn't suzuki also built a featherweight bike with a titanium frame etc at one stage leading to the minimum weight rule coming about. From what I understand titanium isn't ideally suited to mx frames as it is prone to work hardening which leads to fatigue when asked to flex during landing etc
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From what I understand titanium isn't ideally suited to mx frames as it is prone to work hardening which leads to fatigue when asked to flex during landing etc
IIRC you are right - but then if you're a race team just get a new frame ;) :D - which was part of the expense ::) (I think you find even the steel frames are replaced regularly).
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I am unsure about Suzuki but Husqvarna followed BSA and got it right.
Then FIA banned the use of titanium in major components to try and keep the cost of bike racing down.
NASCAR followed FIA and they can not use Ti in major parts to this day.
Ti is certainly cheaper today than back then and we have better methods to join it.
Why am I going on about Ti, simple just about all new header pipes or mufflers are Ti, footpegs, valves and so on.
As we trash these components we will have to replace them or fix them, so now is a good time to start learning. I intend making some trick parts for my VMX bikes out of Ti.
Ji
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I also know of fellow races that use titanium screws, nuts, and bolts on their VMX bikes.
But before we jump feet first into Ti we need to now some of its problems.
First it is not cheap to purchase in comparison to CrMo 4130.
It has to be TIG welded with lots of argon use.
It sparks or flames when bead blasted.
The shavings from drilling, milling or grinding can catch on fire if left in the corner.
It is brittle from the word go. Of course there are a few different grades of Ti some of which are very ductile but we would not be using them for our purpose.
Ji
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Lets also start a list of where Ti parts could be used on a VMX bike for weight savings.
Every nut and bolt,
Spokes,
Spoke nipples,
Rim locks,
Rims,
chain sprockets,
gear shift lever,
Brake lever,
Handle bars,
Hand levers,
Throttle body,
Fork springs,
Shock spring,
Fork dampener rod,
Bash plate,
Air box,
Seat base,
Fuel tank,
Footpegs,
Exhaust pipe including header and muffler,
Exhaust springs,
Engine valves,
Intake manifold,
Axles,
Front number plate,
Cable guides,
Flywheel,
Drive chain,
Chain guard,
Front and rear brake backing plates,
Front and rear brake stays,
Triple clamps,
Front and rear hubs,
Piston,
Clutch basket,
..........
Thank goodness FIA stopped us from making frames out of the stuff.
Ji
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It is difficult to weld it to aluminium but can be done
It can indeed be done but I wouldn't be relying on any aluminium/ti welded joint under even the slightest stress.
The BSA works frames were welded in an inert chamber at the Raleigh bicycle company, one of the few companies in the UK set up to weld Ti successfully in 1965/6. The problems with the Ti frame weren't any deficiencies in the welding itself but with the actual design of the frame. Titanium and Reynolds alloy steel posess totally different stress properties causing the loads to be distributed differently. Because it was new technology the BSA engineers built the Ti frame to the exact same design as the steel version which invariably failed under race conditions. After observing Beezers dramas with the Ti frame Husqvarna realised that it was mainly design deficiencies rather than the actual materials that caused the failures so they designed a frame specifically for titanium and consequently had few problems. Suzuki and Yamaha both experimented with Ti but opted out for various reasons. Suzuki achieved such low weights on their RH/RN works bikes with liberal use of titanium nuts/bolts and fixtures and lightweight magnesium castings. The frames were made from wafer thin chro-mo and were regularly replaced. Pipes often lasted only one moto.
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Suzuki achieved such low weights on their RH/RN works bikes with liberal use of titanium nuts/bolts and fixtures and lightweight magnesium castings. The frames were made from wafer thin chro-mo and were regularly replaced. Pipes often lasted only one moto.
and sometimes the frames didn't even last a whole moto ;)
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FIA is for cars the FIM is for bikes ;D Ti is far from being banned it just isn't used as wisely as thought,as there are better materials. It is banned in the UK from being used for axles, spindles and brake caliper bolts.
Ti work harden??? Commercialy Pure(CP) Ti has so much spring back it's frustrating and labourious to form into any shape other than a circle. Tube takes a lots of force to produce even slight bend arcs without specialised equipment.
Every nut and bolt,
Spokes,
Spoke nipples,
Rim locks,
Rims,
chain sprockets,
gear shift lever,
Brake lever,
Handle bars,
Hand levers,
Throttle body,
Fork springs,
Shock spring,
Fork dampener rod,
Bash plate,
Air box,
Seat base,
Fuel tank,
Footpegs,
Exhaust pipe including header and muffler,
Exhaust springs,
Engine valves,
Intake manifold,
Axles,
Front number plate,
Cable guides,
Flywheel,
Drive chain,
Chain guard,
Front and rear brake backing plates,
Front and rear brake stays,
Triple clamps,
Front and rear hubs,
Piston,
Clutch basket,
except for exhausts, engine valves, fork and shock springs Ti isn't the ideal choice of material for any of those components especialy chains, flywheels and pistons. Aluminium and Magnesium alloys will have less mass and better strength to weight ratios. Ti is 4.5g/cc Al is 2.8g/cc Steel 7.8g/cc and Mg 1.74g/cc. Makes the decision pretty easy.
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Every nut and bolt,
Spokes,
Spoke nipples,
Rim locks,
Rims,
chain sprockets,
gear shift lever,
Brake lever,
Handle bars,
Hand levers,
Throttle body,
Fork springs,
Shock spring,
Fork dampener rod,
Bash plate,
Air box,
Seat base,
Fuel tank,
Footpegs,
Exhaust pipe including header and muffler,
Exhaust springs,
Engine valves,
Intake manifold,
Axles,
Front number plate,
Cable guides,
Flywheel,
Drive chain,
Chain guard,
Front and rear brake backing plates,
Front and rear brake stays,
Triple clamps,
Front and rear hubs,
Piston,
Clutch basket,
What's that a list of Lozza, the things that can, the things that can't or the thing that are made of Ti?
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I remember asking someone why dont they use titanium in the wings of jets and planes,being lighter and stronger that aluminium.
Answer was that titanium gets weaker and more brittle in cold/freezing temps than aluminium,which is more flexible.
Thats what i was told anyway :P
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FIA is for cars the FIM is for bikes ;D Ti is far from being banned it just isn't used as wisely as thought,as there are better materials. It is banned in the UK from being used for axles, spindles and brake caliper bolts.
Ti work harden??? Commercialy Pure(CP) Ti has so much spring back it's frustrating and labourious to form into any shape other than a circle. Tube takes a lots of force to produce even slight bend arcs without specialised equipment.
Every nut and bolt,
Spokes,
Spoke nipples,
Rim locks,
Rims,
chain sprockets,
gear shift lever,
Brake lever,
Handle bars,
Hand levers,
Throttle body,
Fork springs,
Shock spring,
Fork dampener rod,
Bash plate,
Air box,
Seat base,
Fuel tank,
Footpegs,
Exhaust pipe including header and muffler,
Exhaust springs,
Engine valves,
Intake manifold,
Axles,
Front number plate,
Cable guides,
Flywheel,
Drive chain,
Chain guard,
Front and rear brake backing plates,
Front and rear brake stays,
Triple clamps,
Front and rear hubs,
Piston,
Clutch basket,
except for exhausts, engine valves, fork and shock springs Ti isn't the ideal choice of material for any of those components especialy chains, flywheels and pistons. Aluminium and Magnesium alloys will have less mass and better strength to weight ratios. Ti is 4.5g/cc Al is 2.8g/cc Steel 7.8g/cc and Mg 1.74g/cc. Makes the decision pretty easy.
Just because you can, doesn't mean you should :-[
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At no stage did I say all of those parts would be better made in Ti.
This is just a list of components at can be made from Ti that will not breach the FIM rules.
The skin of the new airbus is made from a composite of aluminium and fibre glass.
If that was suggested some time ago people would have said No Way.
Double back flips and forward flips in FMX Again a few years ago most would have said No Way.
The earth is flat.
An MX bike with the exhaust at the rear and the fuel at the front, Come On.
Try and keep an open mind.
Without dreams nothing goes forward.
So using Ti nuts and bolts is a waste of time, very interesting
I will make some phone calls today and see if I can buy some magnesium nuts and bolts
Ji
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Graeme, that was just a list of components Ji thought might be worthwhile making from Ti. Basicaly unless very high temps (or making a spring)are involved Aluminium is a better choice, Mg bolts don't exist as Mg isn't a ideal material for bolts, Al , Ti, CrMo or steel are best for any load bearing application. Monaro Ti is NOT lighter than aluminium it's lighter than steel and twice the mass of aluminium and about 10 times the cost.Pure Ti is a very resilient material Ti is very difficult to cast in intricate shapes(golf clubs aside) unlike other materials
There will be a good reason why something like a Ti chain has never been used before, even in 'money is no object' racing like MotoGP a Ti chain has never been used.Ti nuts and bolts are lighter than steel but not as light as 7075 or 2027 Al bolts and nuts.
I might save 2.5kgs from using Ti bolts in a bike cost say $1000, but the juice isn't worth the squeezing.As the overall power to weight ratio doesn't change that much.
Bike 100kgs with 20HP has 0.2kg/HP power to weight ratio.
97.5kg bike with 20 HP has 0.205 kg/HP power to weight ratio
100kg bike with 21HP has 0.21 kg/HP power to weight ratio.
That can be done for far cheaper than a wheelbarrow full of Ti.
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Density Yield Strength Mod of Elastity Strength -Weight Ratio Stiffness to Weight Ratio
CrMo 4130 7833 kg/m3 620MPa 210GPa 0.079 0.268
Ti Grade 5 4428 kg/m3 827MPa 107GPa 0.186 0.0241
Al 6061 T6 2707 kg/m3 275MPa 67GPa 0.1015 0.0247
I have compiled the above chart.
All three materials have about the same stiffness to weight but Titanium wins the race when it comes to strength to weight ratio.
Ji
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Lozza, as usual, is correct.
Things like a chain would not be worth while doing unless you combine other materials or change the design. Pistons are made from titanium as Ti has a very low thermal expansion.
Carbon fibre is even better than all these materials when used in the right location.
Can you imagine having titanium tyres.
But you could use titanium as the reinforcing for the tyre.
Two different ways of looking at the same problem.
Ji
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Graeme, that was just a list of components Ji thought might be worthwhile making from Ti.
Ah eh, I wasn't paying attention was I. ::)
I think weight saving is an interesting subject especially for MX. It doesn't just effect acceleration (power to weight), but also braking, steering/handling and suspension performance. I think it is well worth the effort and the money (within reason ;)) - and chase the ponies ;) ;D (but I would rather have a light weight bike with moderate power rather than a perky, powerful overweight pig ;D).
Concentrating on unsprung weight would always be a priority. I'm particularly curios about Ti spokes and nipples. It not hard to imagine taking a kilo of both wheels (for no loss of strength?). I once read of a Henry prepared road Duke that had them. The works Hercules of the '70's also used them.
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And sheding a kilo of unsprung spinning weight is worth 2 kilos of unsprung weight, like in the case of titanium reinforcing in the tyres, spokes and nipples.
Do you think the F1 designers sit around saying "Just because we can doesn't mean we should"
With that attitude they would not be around for very long.
Take Rossi's engineer he is always thinking of ways to get more speed from the bike.
Ji
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Bike 100kgs with 20HP has 0.2kg/HP power to weight ratio.
Shouldn't this be 0.2hp/kg which is power to weight ratio.
Ji
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Hi Walter,
In my case if you have seen my racing videos I think the most weight on the bike is sitting on the seat.
I am doing a comparison right now so I will let you know soon.
Ji
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Intermission .....
Have just received a 1968 magazine on the Sprite/AE and its saying; A point that struck us was the workmanship.All welds are heliarc............What a heliarc ???
thanks --resume transmission--
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Lets take a look at a very simple part that can be replaced by Ti.
The front brake stay on a 1977 Maico.
From the factory it was made from aluminium and weighs 82g.
The stay has a typical cross sectional area of 0.000108 square meters and is 250mm long.
To check weight we multiply the cross sectional area by the length by the density of aluminium.
0.000108x0.25x2700 = 0.0729kg or 73g
The stay has a cable connector and alignment spacer so this would be close to its actual weight of 82g.
This stay is in tension when the brakes are applied so the cross sectional area at the weakest section is at the connecting bolt.
The area is 0.00006 square meters.
To reverse engineer this component we apply the following.
area x tensile strength = force
Aluminum 6061 T6 yield strength 275mpa permissible strength for axel tension = Fy 0.6 = 165mpa
0.00006 x 165 = 0.0099kn
To produce the same load carrying capacity using Ti grade 5 yield strength 827MPa or Fy 0.6 = 496MPa
area = 0.0099/496 = 0.0000199 square meters
If we apply this to the typical cross sectional area but this time using bending moment instead of tension we find the following.
The original cross sectional area could be reduced to one third of the original size.
0.000108/3= 0.000036 square meters.
Now to do the calculations to determine the weight of this product in Ti
0.22x0.000036x4428= 0.035kg or 35g
0.03x0.0000199x4428= 0.0026kg or 2.6g
Plus the extra weight for the cable connector and spacer 14.7g
Total Ti weight = 52.3g
Weight saving = 29.7g
That is a weight saving of 36% of unsprung weight.
These calculations should not be used until checked by a registered engineer.
These calculations have been supplied for demonstration purposes.
Ji
(http://i726.photobucket.com/albums/ww268/Jigantor1963/Stay1a.jpg)
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Intermission .....
Have just received a 1968 magazine on the Sprite/AE and its saying; A point that struck us was the workmanship.All welds are heliarc............What a heliarc ???
thanks --resume transmission--
http://www.advantagefabricatedmetals.com/tig-welding.html
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Alison....Heliarc is an old generic term for TIG welding from the days when they used helium instead of Argon. The yanks still use the term even though helium hasn't bee used in decades.
A point that struck us was the workmanship.All welds are heliarc...........
That's interesting, I've never seen a "heliarced" AE/Sprite, Frank Hipkin, the Sprite manufacturer told me that the early frames were brazed then they switched to MIG welding for the fastback frame. My frames are both brazed and they're both pre '70 early frames.
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I was involved with the cross country mountain bike scene over the last few years and I have seen a lot of people spending a lot of money chasing weight savings. One of the cheapest ways to save weight is to make sure your not overweight yourself!!! By the way given that you are not overweight ( and I am!) and you want to save some bike weight what about carbon fibre for some components, Just a thought. Cheers Jerry
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All this talk about grams of weight saving is a bit pointless i say on an old girl that has a old bloke who is knackered on the 2nd lap, ok mybe 3rd if he is under 40, cant we just ride them instead of all this talk.......... it hurts my head. next youll be telling me to loose my original airbox cos it weight 100 grams, my body armour weights 10 times more than that.
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No one is telling any one here to do anything.
The Pre 90 Grand Prix race I entered at Conondale last month went on for 15 minutes plus 1 lap.
I am 47 years old office worker.
The temp was 29 deg C with 95 percent humidity.
I lost 3 kilos of fluid just in the 12 minute practise.
Shedding weight and improving suspension all helps you ride the last lap as safe and quick as the first.
Ji
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All this talk about grams of weight saving is a bit pointless i say on an old girl that has a old bloke who is knackered on the 2nd lap, ok mybe 3rd if he is under 40, cant we just ride them instead of all this talk.......... it hurts my head. next youll be telling me to loose my original airbox cos it weight 100 grams, my body armour weights 10 times more than that.
It's called .....(http://i323.photobucket.com/albums/nn458/mx250syd/OzVMX/E9622_106414468434a33862c3a9.gif)
Ya trying to spoil our fun Freaky >:(
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Ji did you have scales there at the meeting to weigh yourself in anticpation of the weight loss? How did you rehydrate? Did you use water or Poweraide or simiiar? Jerry
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Hi Jerry,
Yes I take scales.
Water and Staminade.
I also eat gell.
Ji
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As interesting as Ji's posts are, aren't we forgetting that this is vintage motocross not F1 or Moto GP. I fail to understand why anyone would even consider this stuff for a VMX bike unless it was on the bike in the first place or you're building a replica of something trick that was available back then. My Boyd and Stellings TM had a full complement of Ti bolts and nuts which I replaced with good old heavy as shit steel in the interest of safety. I've kept the period Ti brake pedal for the cool factor and the fact that I'm too lazy to make a new one but frankly I think it's a bit of a wank. You'd be living in Fantasyland if you thought that spending serious money on titanium to save a few grams is going to make your bike faster or better handling. It's got a bit of wow factor to some folks but it's not even bling in a shiny sense.
IMHO VMX isn't the correct platform to experiment with turning out bikes into exotic spaceships bearing little comparison with what we used in the bikes's glory days. Like Jerry said, if you want to save weight, go on a diet, if you want to go faster, go to a riding school.
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Here's another weightsaving tip. Shave all body hair (particuarly if you are of European extract, void bowels and bladder and if you really serious about weight saving only have enough fuel for your race and not for the whole meeting (much less unsprung weight!) Jerry
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Okay lets all use the factory suspension, F... off those Simons forks and Fox rear air shocks.
Lets all use factory exhaust pipes.
We should also use clothes that are period, see ya leatt.
How many people that say stop trying actually race any more.
Ji
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No Jerry those are sprung weight.
Ji
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Thanks Firko you picked up my point exactly. Having said that I have wondered if I won the Lotto just how light I could make old Fang the Sang? Of course I could also afford a personal trainer to assist me to motivate my sorry arse to lose 10 kg or so. Then maybe I could get someone to teach me some bike riding skills too. Bugger it I might just go and have a beer. Cheers Jerry
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Okay lets all use the factory suspension, F... off those Simons forks and Fox rear air shocks.
Lets all use factory exhaust pipes.
We should also use clothes that are period, see ya leatt.
Give me a break.....all of those things you mention, Simons forks, Fox Shox and so on were all available during the era the bike raced. I build bikes as trick or even tricker than most but I NEVER use technology I couldn't buy during the bikes competitive era. Making stuff out of Ti is not in the spirit of vintage motocross unless you're replicating parts that were made from Ti during the era. I believe you're turning bikes into something they never were. It's merely a platform to show off your own abilities. If that's the reason for using exotics, go modern racing where it's more appreciated.
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How about Glenn Bells wave front disc at the nationals last year.
Every one has told me that that was totally legal.
If it is within the rules you can do it.
BSA and Huskys used Ti.
Roger De's Suzuki was not even for sale so back then they were building their own parts.
Ji
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Walter,
Lets use my Maico again.
Its rear axel is 290mm long and is 17mm diameter CrMo.
It came from the factory solid but two years ago I bored my out.
So now it has a 12mm diameter hole in the centre.
Original weight 1777g
Bored weight 885g
Weight saving 892g
49% saving.
There would be a small saving using Ti but as all the knockers keep saying and in this instant I agree it would not be worth the trouble.
Ti would be 500g bored out, a total saving of 1277g
I do not advocate boring out your axels this is just what I have done.
Ji
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I build bikes as trick or even tricker than most but I NEVER use technology I couldn't buy during the bikes competitive era
How about plastic mud guards and air boxes on Bullies? They had fibre glass ones
How about PD valves?
If I had time I am sure there is a huge list of parts that are used now that were not around in the day.
Ji
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Re read what you wrote Ti......everything you said about BSA and Husky and even Rogers Suzuki (of which I don't get your point but whatever..) backs my point. All of those things, the ti frames were available in the day. What you're doing is reinventing the wheel by building Ti bits today that were never available back in the day. I'll repeat myself..VMX is not the place for new technology.
That wave disc is in my mind not legal but I wasn't the scrutineer so I'll bow to his opinion. However, I reckon it's a long way from being in the spirit of VMX. There was no need to use a wave disc when a conventional disc would have worked just as well and would have made the bike look far more in keeping of its era. The fact that the rulebook allowed the wave disc is more about the book not covering certain areas because if the inadequacy of the regs rather than the book specifically saying "Yep Geoff, you can run a wave disc on your Honda old mate, good on you for finding a loophole".
Vintage racings about capturing the feel and technology of an era, not building parts that have not relationship to the era.
Actually I enjoy Gigantors posts , its quiet a change from reading E-bay stories. There no rule that you HAVE to bling up your bike , but there also no rule that you cant. A nice restored or era correctly blinged up bike makes me stop and admire it everytime. But thats me , I like when people take pride in things they do . Dont stop Robert , there is a few that enjoy your work
I agree, I enjoy Roberts posts but sometimes we need to stop and think about what our sport's about. Because the rulebook doesn't say you can do it doesn't make it morally right. If that was the case, I might as well build a carbon fibre tank and bodywork, titanium frame and cast up mag cases and hubs for my upcoming Metisse. Sure it's not going to happen but I could if I was rich and didn't give a shit about tradition. Why could I do it? Because the rulebook doesn't say I can't. Imagine the shitfight If I turned up with that bike?
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It's only a shitfight if you got found out Firko. If I was going to spend a shitload on lightening a bike and using exotic unobtanium etc and therefore well and truly encroaching on the spiit of VMX I would then have to go the whole hog and disguise the components so they "look heavy" and then hope like hell that no one has a set of scales handy.Cheers Jerry
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Okay so some things were made back then and some were not.
I am sure if you scanned every MX magazine going back to when ever the first one rolled off the presses you could find some engineer has made just about every part.
I am not saying I am the first to do any of this stuff, I am just exploring what can be done.
My point was if you fit new plastic mud guards to a bultaco it is no longer in the sprit. There may have been after market plastic ones available a few years after their release but that would not be in the class for some bikes.
Ji
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This is going to bring on the hurt.
I my opinion the class scrutineering at the 2009 VMX nationals was a joke.
This is as you say was because of the rule book. Well the rules need changing.
Until then I will make parts just like every one else.
Who hasn't drilled out a bolt?
You say hang on that was done by Roger's engineer in 1976 as illistrated by MX Monthly.
So if you drill out a bolt you now have to take a copy of an old magazine to every race ready just in case someone sees it. Get Real.
Ji
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I give in.....I've argued this point so many times it's like talking to a shed full of bowling balls. While I really do give a shit about this stuff infiltrating the sport I love, my sprouting off on a bloody forum isn't going to change diddly squat. My concept of the sport is light years different to yours Ji. The hollow axle on the Maico thing broke me. I'm laughing and crying at the same time. The sad thing is that I know you're dead serious........I'm off out to the shed to work on my bike for CD7 (and polish the titanium brake pedal on the Boyd and Stellings. ;D)
ps...For what it's worth...I had a period aftermarket hollow Chro-Mo axle on the rear of my Champion Honda MXer. It lasted three laps of Amaroo Park before it bent like plasticine. I needed to oxy cut the bloody thing out.
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My Maico Axel while installed on the bike has ridden at Conondale 3 times since I bored it out.
Conondale Classic
CD6 &
The 2009 VMX nationals.
Still going as before.
This is not a fight with you mate just telling it as I see it.
Ji
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Can i just say ( and i have been meaning to post this for a while) was the scuitineering for the 2010 Nats was the best i have ever seen, fast easy and no bullshit, you walked up they looked at the bike, you walked off. The guys were smart enough to see if the shit that mattered worked and if it looked right, then you walked off. THAT is HOW it Should be, hats off to you Tanner and fat boy.
PEople dicking around with screw drivers on your spokes and tape measure is a freakin waste of time and all you end up with is a line so big it takes an hour to get one bike through and that sucks if you have 3 and your first race.
These guys looked at the right stuff and if there was any doubt you were taking out of the line and asked to make right, while the rest of the line kept moving. thanks christ someone is finally getting this part sorted out, it makes the event enjoyable again.
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Firko that is bowling balls covered in concrete skins............. "Period machines" what is so f@%king hard to understand ??? Ji your info is very entertaining and somewhat informative .But ...... you know the old " cannot see the forest for the trees thing...... How about some info on bronzing or braising Renolds tubing of the sixties /seventies era for balance sometimes?
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Tim,
I am not the only one on this forum with a camera and a blow torch.
Those that are expert in brazing renolds should start a topic just like what I have done.
I start topics about what I know and what interests me.
Ji
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Re read what you wrote Ti......everything you said about BSA and Husky and even Rogers Suzuki (of which I don't get your point but whatever..) backs my point. All of those things, the ti frames were available in the day. What you're doing is reinventing the wheel by building Ti bits today that were never available back in the day. I'll repeat myself..VMX is not the place for new technology.
I have to thank Firko and many more members on this forum for educating me on the 1965 titanium framed BSA MX bikes. From that education and some I have done indipendently I know that BSA made just about every part of those bikes from titanium including the crank shaft and conrod. What does this mean, it means that the gear shift lever, brake lever, brake rod, brake stay and so on were made out of titanium back 1965. FIM did ban titanium as a material for the major components ; frame and swingarm.
Other than that this material can and was used by other race teams back in the day.
I am not reinventing the wheel nor is this a new technology.
Some CZ's came out with the levers perch welded onto the handle bars though I saw the national winner using modern Fat Pro Taper bars on his CZ.
Some of our rules contradict this spirit or moral judgement.
1 We have to run a handle bar pad
2 We have to install a chain guard
My Maico never came out with either and I am not even sure there was an aftermarket part back in the day.
To put an end to all this why don't we change the rules to say your bike must be as per when it left the factory.
Ji
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I have just found out I have to have a knee replacement. Does anybody know what material it will be made of and whether you can get a lightweight trick one. I already have a titanium screw in my shoulder and it definitely works better than the original old school heavy bone model! Jerry
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I have just found out I have to have a knee replacement
How weird.....I've just returned from a 2.30 appointment at the specialist where I was given the same prognosis. I'm getting an ankle fusion as well to top it all off. I want titanium, none of that old fashioned heavy stainless steel or ceramic shite for me. :D
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Heh Firko had an arthroscopy last Friday. Had the opportunity to stay awake (spinal block) and watch it on TV. Facinating stuff. If you ever get the chance do it you wont regret it plus it gives you the chance to stick it up all the soft cocks who have to have a general. Cheers Jerry
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adam scard who is not on here any more use to make all these human spare parts firko ive got his email if you need a knee
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I have bandy legs ( which probably caused the problem in the first place, wish mum and dad had put me in calipers!) Can you get an offset knee joint to compensate for my poor alignment? Jerry PS Sorry Ji we have got away from your thing a bit
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To put an end to all this why don't we change the rules to say your bike must be as per when it left the factory.
Yeah 'cause it's a whole lot harder to put a chain guard and bar pad on a bike than it is to make it OEM again...... ??? ???
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Had the opportunity to stay awake (spinal block) and watch it on TV. Facinating stuff. If you ever get the chance do it you wont regret.....
Pass. Excuse me, I'm feeling......... (http://i323.photobucket.com/albums/nn458/mx250syd/icons/sick.gif)
;D.
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adam scard who is not on here any more use to make all these human spare parts firko ive got his email if you need a knee
im Sure he could, last i heard he sold them on the side too, ( which is why he....well lets say moved on ) ;)
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To put an end to all this why don't we change the rules to say your bike must be as per when it left the factory.
That would never be possible. That would wipe out more than 75% of the field with modern shocks. I wouldnt mind seeing restrictions on modern shocks but its never gonna happen,they are here to stay, just like theres never going to be an all OEM rule. We have to live with the current rules as they are and if people want to put modern fat bars on or carbon fibre stuff that totally looks silly and out of place then let them do it. Just build your bikes how you want to build them and keep within the rules.
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Thats where I was going with this thread.
Ji
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This topic has become so long and diluted that I am going to remove it from the forum in two days as it no longer serves any purpose.
Ji