OzVMX Forum
Clubroom => Tech Talk => Topic started by: sleepy on February 11, 2016, 12:03:07 pm
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Just thought I'd share the latest bit of butchery I have come across.
Had an RM125B crank turn up for a rebiuld and the first thing that looked funny was the rub marks on the sides. Measuring it I found it to be almost 1mm wider than others I had seen. After it pressed apart I found a stepped pin and a later rod fitted with a larger big end bore. Thats ok but the thrust washers were to big for the recess and that's why it was to wide. The next strange thing was the appearance of the wear on the pin, looked almost like it had milled flats machined into one side which I hadn't seen before. The pin had been properly made by the look of the grinding finish on the un-worn sections but after a quick file test I found it hadn't been hardened.
Makes me groan to see stuff like this and am amazed at how shops could charge for such work.
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That's kind of perversely impressive.
I'd hazard a guess that a bike shop (or "helpful" uncle) farmed the machine work out to someone who didn't know what they were building.
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Bloody sad really >:( :( Still I think there seems to be a lot of hospital surgeons that caught the same plane......
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Thought I'd upload a photo(if it works) of the pin. Also pretty sure I know who made it or at least who sold and had it fitted, won't post the name publicly.
(http://i1078.photobucket.com/albums/w490/Georgem15/Bigend%20pin.jpg) (http://s1078.photobucket.com/user/Georgem15/media/Bigend%20pin.jpg.html)
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Iv'e seen it but I don't believe it :o ahh yes I do, recently bought a YZ80C fuba come's to mind to give you an idea of dodgie back yard work done to it both front and rear brake actuator arms are welded on :-\
still I got what i paid for! well almost, maybe :-[
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Iv'e seen it but I don't believe it :o ahh yes I do, recently bought a YZ80C fuba come's to mind to give you an idea of dodgie back yard work done to it both front and rear brake actuator arms are welded on :-\
still I got what i paid for! well almost, maybe :-[
I'd forgive a back yarder for this type of work but it didn't come from one.
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Thought I'd upload a photo(if it works) of the pin. Also pretty sure I know who made it or at least who sold and had it fitted, won't post the name publicly.
(http://i1078.photobucket.com/albums/w490/Georgem15/Bigend%20pin.jpg) (http://s1078.photobucket.com/user/Georgem15/media/Bigend%20pin.jpg.html)
That can't have been heat treated correctly/if at all :o The bearing has just been rocking back and forth. Had the big end disintergrated?
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That can't have been heat treated correctly/if at all :o The bearing has just been rocking back and forth. Had the big end disintergrated?
The rod and bearing look quite ok. Definetly not heat treated or completly wrong steel used. The quality of finish on the pin is quite good but that didn't help the poor guy that paid good money for a crank build.
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Who ever produced this has thought of it only as a crankshaft pin, Instead of a crankshaft pin and Bearing journal
Hardened bearing journals don't disintegrate in the way that this surface has.
(http://i1078.photobucket.com/albums/w490/Georgem15/Bigend%20pin.jpg)
Although Bearing Manufacturers use slightly different nominations of high carbon high chrome steels.
52100 bearing steel is a good choice for such one offs.
It will still produce a very good high performance result.
A couple of reasons why:
52100 will machine well in the hands of any competent turner.
No need for induction hardening(as performed by manufactures prior to grinding).
It can simply and safely be case hardened at home.
Then sent to a Cylindrical grinding machine to finish the bearing journal surface.
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Steel is no longer malleable after hardening.
These raised up ridges are a characteristic indication of still malleable
(http://i677.photobucket.com/albums/vv132/mc125mick/Bigend%20pin_zpsskemeppo.jpg~original)
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Who ever produced this has thought of it only as a crankshaft pin, Instead of a crankshaft pin and Bearing journal
Hardened bearing journals don't disintegrate in the way that this surface has.
(http://i1078.photobucket.com/albums/w490/Georgem15/Bigend%20pin.jpg)
Although Bearing Manufacturers use slightly different nominations of high carbon high chrome steels.
52100 bearing steel is a good choice for such one offs.
It will still produce a very good high performance result.
A couple of reasons why:
52100 will machine well in the hands of any competent turner.
No need for induction hardening(as performed by manufactures prior to grinding).
It can simply and safely be case hardened at home.
Then sent to a Cylindrical grinding machine to finish the bearing journal surface.
I have a piece of EN36A sitting here waiting to be turned into oversize pins. The plan is to machine up a batch of 24 and 25mm pins that are .5mm oversize, get them case hardened and then grind to suit honed out rods for hard to get stuff. It's a good way to bring back cranks that are worn but only if they haven't had an overheat. Just got to get the time to do it and decide what to make them for.
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I have a piece of EN36A sitting here waiting to be turned into oversize pins. The plan is to machine up a batch of 24 and 25mm pins that are .5mm oversize, get them case hardened and then grind to suit honed out rods for hard to get stuff. It's a good way to bring back cranks that are worn but only if they haven't had an overheat. Just got to get the time to do it and decide what to make them for.
That's a great time saving alternative for blokes like me in those difficult to get rod situations Sleepy.
I am not quite set up to do it.
So the next one that is difficult to find, but existing is savable, you will be hearing from me :)
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rather than making a pin from scratch, if this engine has been fitted with a later rod, which has a larger big end, could you use the matching pin for that rod and machine out the crankshaft halves to suit that ?
{assuming there is enough space/clearance to do this}
or make a stepped pin out of the later type pin ?
at least it would be the correct material and the bearing area wouldn't need machining
just a thought { I am usually wrong on this sort of subject}
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rather than making a pin from scratch, if this engine has been fitted with a later rod, which has a larger big end, could you use the matching pin for that rod and machine out the crankshaft halves to suit that ?
{assuming there is enough space/clearance to do this}
or make a stepped pin out of the later type pin ?
at least it would be the correct material and the bearing area wouldn't need machining
just a thought { I am usually wrong on this sort of subject}
Machining the crank wheels is the way I normaly do it if the original is no longer available and there are others available that match the lenght but with bigger pins. The owner of the crank in this case managed to find a NOS rod which has been fitted.
The stepped pin option is OK if made properly but each time a new rod kit is needed a new stepped pin is needed as well but with machined out wheels the new kit goes straight in.
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Only the bearing journal need be hardened made heaps of stepped pins that way. There should always be a small radius from the journal to the step down EDM wire cutting the crank webs works very well too. Mick the pin must be hardened and EN36 A/B is the only material to make it from. Has to be hardened then ground to final size.
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rather than making a pin from scratch, if this engine has been fitted with a later rod, which has a larger big end, could you use the matching pin for that rod and machine out the crankshaft halves to suit that ?
{assuming there is enough space/clearance to do this}
or make a stepped pin out of the later type pin ?
at least it would be the correct material and the bearing area wouldn't need machining
just a thought { I am usually wrong on this sort of subject}
Machining the crank wheels is the way I normaly do it if the original is no longer available and there are others available that match the lenght but with bigger pins. The owner of the crank in this case managed to find a NOS rod which has been fitted.
The stepped pin option is OK if made properly but each time a new rod kit is needed a new stepped pin is needed as well but with machined out wheels the new kit goes straight in.
Was the NOS rod RM 125B rod? RM 125B pins and big end bearing should still be available? Not sure why would some one made stepped pin for this application.
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I'd forgive a back yarder for this type of work but it didn't come from one.
As a backyarder, I couldn't even forgive myself, for that kind of work. :o
Cheers, Daryl.
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rather than making a pin from scratch, if this engine has been fitted with a later rod, which has a larger big end, could you use the matching pin for that rod and machine out the crankshaft halves to suit that ?
{assuming there is enough space/clearance to do this}
or make a stepped pin out of the later type pin ?
at least it would be the correct material and the bearing area wouldn't need machining
just a thought { I am usually wrong on this sort of subject}
I think it is an RM125B. I haven't tried Suzuki to check stocks but they could have been in a big hurry to get it going.
I recently converted a set of RM125B wheels to take the latter rod but it was done that way to recover wheels that had be badly broached. I could have sleeved the wheels but that would have been more costly. Also the later rod with bigger pin and nice silver platted cage is a more robust unit. The stock RM bearing when used in road race can't handle the extra RPM that is needed to be competitive.
Machining the crank wheels is the way I normaly do it if the original is no longer available and there are others available that match the lenght but with bigger pins. The owner of the crank in this case managed to find a NOS rod which has been fitted.
The stepped pin option is OK if made properly but each time a new rod kit is needed a new stepped pin is needed as well but with machined out wheels the new kit goes straight in.
Was the NOS rod RM 125B rod? RM 125B pins and big end bearing should still be available? Not sure why would some one made stepped pin for this application.
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I'd forgive a back yarder for this type of work but it didn't come from one.
As a backyarder, I couldn't even forgive myself, for that kind of work. :o
Cheers, Daryl.
Yes Daryl but as a backyarder your engineering knowlege is better than most.
They say that a good engineer is not one that knows everything but knows how to find the correct information.
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8620 is another suitable case hardening steel.
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8620 is another suitable case hardening steel.
I'll stick with the EN36 it has a better core strenght and fatigue resistance according to the specs. My theory is you are going to the trouble to make a part use the best material available and know it will work.
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8620 is another suitable case hardening steel.
All crankpins and gears are made from EN36 .....for a very good reason they harden very well but stay ductile under the hardening. No gear cutter will use anything else.
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I would be wanting the correct material used, if and when the time comes for the dearest option to replace a no longer available Transmission gear with a one off make?
All steel alloy manufactures who produce EN36 say it is not for transmission gears, because it has a chromium content.
All steel alloy manufacturers of EN series under the British Standard BS970 recommend EN34 as the correct stock for transmission gears(Zero Chromium).
Yet you say
All gears are made from EN36 ...... No gear cutter will use anything else.
Can you show me some documentation or a valid link to one manufacturer of alloy steel that says otherwise than what I have stated? Just one?
In the absence of proof? Can you tell us which "gear cutters" are ignoring the manufacturers of EN36 instructions and advise, so we can avoid them please.
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I would be wanting the correct material used, if and when the time comes for the dearest option to replace a no longer available Transmission gear with a one off make?
All steel alloy manufactures who produce EN36 say it is not for transmission gears, because it has a chromium content.
All steel alloy manufacturers of EN series under the British Standard BS970 recommend EN34 as the correct stock for transmission gears(Zero Chromium).
Yet you say
All gears are made from EN36 ...... No gear cutter will use anything else.
Can you show me some documentation or a valid link to one manufacturer of alloy steel that says otherwise than what I have stated? Just one?
In the absence of proof? Can you tell us which "gear cutters" are ignoring the manufacturers of EN36 instructions and advise, so we can avoid them please.
Albins Modena and Coljen all use EN36.Feel free to ask. All the gear I've had Col make are made from EN36. Pretty sure Ellis Moore in the UK uses EN36.
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Yes sure EN36 is a great choice for vintage Crank pins, but it is not the only available choice, by far.
This
All crankpins are made from EN36 ....
is just simply Not True.
EN36 is only one choice of several different but still suitable offerings from different manufacturers.
It is just not a matter of "Standards" either.
JIS SCH420H varies slightly in content, performance and working requirements to EN36 as does alloy made to the American Society standard of ATSM-4115
All slightly different.
Sometimes it is
Bang for buck, adequate performance, built to a price.
Or
Superior performance, built to a higher price.
For example,
Hot rods use ATSM-4115 for Crank-pins
http://www.hotrodsproducts.com/productinfo.aspx?cat_details_id=34 (http://www.hotrodsproducts.com/productinfo.aspx?cat_details_id=34)
Royal Rods use SCH420H for their Crank-pins
http://www.con-rod.com.tw/products.htm (http://www.con-rod.com.tw/products.htm)
There are other Crank-pin manufacturers who don't use EN36 either, so these facts are a along way from
EN36 A/B is the only material to make it from.
All crankpins are made from EN36 ....
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Albins Modena and Coljen all use EN36.Feel free to ask. All the gear I've had Col make are made from EN36. Pretty sure Ellis Moore in the UK uses EN36.
I don't know who these people are lozza, and maybe sadly, but I don't care either.
Maybe they should submit their CV's to all of these Steel Alloy producers and tell them how wrong they are doing it?
In the UK hey? Ok,
Well in that case I will go with one of the UK companies, say "Yorkshire Steel"
Here is the link, they all tell the same story
http://www.westyorkssteel.com/alloy-steel/case-hardening-steel/en34/ (http://www.westyorkssteel.com/alloy-steel/case-hardening-steel/en34/)
And in all fairness I used that link because there is also the goodies there on EN36
As I basically said, "if I were going through that expense for a gear? I would want the most durable outcome and the correct one.
And as I also said and still think it is a great path to tread when required
I have a piece of EN36A sitting here waiting to be turned into oversize pins. The plan is to machine up a batch of 24 and 25mm pins that are .5mm oversize, get them case hardened and then grind to suit honed out rods for hard to get stuff. It's a good way to bring back cranks that are worn but only if they haven't had an overheat. Just got to get the time to do it and decide what to make them for.
That's a great time saving alternative for blokes like me in those difficult to get rod situations Sleepy.
I am not quite set up to do it.
So the next one that is difficult to find, but existing is savable, you will be hearing from me :)
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I'd have to agree with Mick that there are a number of different steels would do the job for a bigend pin. Localy here is Brisbane we don't to many choices but can get EN36A.
As for gears a number of years ago I had some gears made for a speedway car that I built the engine for. The motor was a turbocharged and supercharged GS750 with reduced bore to 700cc. It was making upto 240hp at the tyres although not often raced at that boost level for traction reasons.
The gears replaced 2nd gear and were about 1.75 times as thick. The first batch were made out of EN36A and case hardened to .020" giving HRC 58. They lasted quite well but still failed by breaking teeth( out lasted stock 10 times).
A 2nd batch was made this time by myself and I used E110 and case hardened to .030" with HRC 60 , they were also cryo treated and shot penned and they are still in the engine but it has not been used for a few years now. A set went into a GS1000 speedway engine as well and I have 1 set still here if anyone want them.
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without yet reading it all i may as well get shot down in flames lol. Ran a VW king pin as a big end pin in my Mk8 Pursang which was a couple of thou bigger after i'd had the original out & in too many times & just wasn't tight enough to be safe. What was 'that' VW pin made of?. Wonder who bought it after i'd finished with it--bad man 'me'. Loved that bike & raced it from new. Just kept fixing it--if ya call that fixing it. Might've got two pins out of one king pin but too long ago to remember. Can remember going around town with a micrometer annoying everyone with stupid questions. Then i got an MX250B.
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Albins Modena and Coljen all use EN36.Feel free to ask. All the gear I've had Col make are made from EN36. Pretty sure Ellis Moore in the UK uses EN36.
I don't know who these people are lozza, and maybe sadly, but I don't care either.
Maybe they should submit their CV's to all of these Steel Alloy producers and tell them how wrong they are doing it?
In the UK hey? Ok,
Well in that case I will go with one of the UK companies, say "Yorkshire Steel"
Here is the link, they all tell the same story
http://www.westyorkssteel.com/alloy-steel/case-hardening-steel/en34/ (http://www.westyorkssteel.com/alloy-steel/case-hardening-steel/en34/)
And in all fairness I used that link because there is also the goodies there on EN36
As I basically said, "if I were going through that expense for a gear? I would want the most durable outcome and the correct one.
And as I also said and still think it is a great path to tread when required
I have a piece of EN36A sitting here waiting to be turned into oversize pins. The plan is to machine up a batch of 24 and 25mm pins that are .5mm oversize, get them case hardened and then grind to suit honed out rods for hard to get stuff. It's a good way to bring back cranks that are worn but only if they haven't had an overheat. Just got to get the time to do it and decide what to make them for.
That's a great time saving alternative for blokes like me in those difficult to get rod situations Sleepy.
I am not quite set up to do it.
So the next one that is difficult to find, but existing is savable, you will be hearing from me :)
Albins have made gear sets for just about every rally car that finished a stage in Australia and make the gear sets for the Nissan V8 supercar.
Modena more for you high end Ferarri's and such. Modena made a very trick ICC kart gearbox that allows flat shifting up and down the gearbox without electronic intervention
Coljen for motorcycles and superkarts in Australia.
Ellis Moore makes 90%of the gear sets for classic bikes in the UK.
EN36 no good for crank pins, better go onto Kiwibiker forum and explain that to Wayne "Wobbly" Wright(ex GP engineer/BSL 500 designer) he has it all wrong and shouldn't have made all those crank pins from EN36
how would they get it all wrong at the same time?
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EN36 no good for crank pins, better go onto Kiwibiker forum and explain that to Wayne "Wobbly" Wright(ex GP engineer/BSL 500 designer) he has it all wrong and shouldn't have made all those crank pins from EN36
Never once at any time did I say EN36 is no good for Crankpins, Did I? Well?
Lets keep this simple as to avoid more of your misstruths.
I said EN36 is not the only choice of material for crank pins and no doubt you are well aware of exactly that, all knowing of everything!
So show us where I said EN36 is no good for crankpis, without lying this time.
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On a brighter note the guy with the RM crank picked it up today and was very happy to have a useable crank again.
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Mick if you have any suggestions as to which model oversize pins I should make I'd like to here them.
I was thinking some 24 and 25mm generic pins but after hearing the cost of the 125 Husky rod kits perhaps I should make a couple of those as well.
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Should've gone to specsavers Lozza...
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8620 is another suitable case hardening steel.
All crankpins and gears are made from EN36 .....for a very good reason they harden very well but stay ductile under the hardening. No gear cutter will use anything else.
There is 'better' material than EN36 available with higher surface hardness, higher fatigue strength and higher core strength, Ferrium C64 is one. This boutique triple vacuum remelt steel is not so easy to obtain. For the relatively lightly loaded solid or near solid pins in a 2 stroke crank the core strength of the steel is not critical compared with say, a gear, whose teeth have to resist bending loads. What matters is the hardness, cleanliness and fine grain size of the carburised layer. In other words the quality of the steel is the most important factor. From that point of view high quality 8620 will be a better choice than a cheap EN36B/9310.
Australia's pemium race gearbox builder has long been Holinger Engineering. I had a conversation with Peter Holinger about the world renowned H6S V8 Supercar gearbox that he designed and started making in the 90's. He said that a lot of it's reputation for unbreakable reliability up to it's design limit, was because Corus, formerly British Steel, supplied them with special high purity EN36 and EN39 which was then heat treated to very rigorous specifications.
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I can't begin to say how much I've enjoyed reading this thread! 40 years ago I did a 3 year DLI welding course (and never used the skill/knowledge in the workplace), but really enjoy the discussion around metallurgy and the physical properties of metals.
I did use some of my outdated knowledge on the cracked Reynolds 531 frame of my Rickman CR750.
"... and now back to your scheduled programming..."
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All this sounds very expensive and I am pretty sure that it is easier, cheaper and quicker to just bore out/sleeve crank halves(very simple procedure anybody with a lathe can do) and use readily available parts. Rod width and pin length can be easly modify by anybody with basic turning skills. Also labour cost in Australia is astronomical for making such parts so it does not matter what material you are going to use.
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All this sounds very expensive and I am pretty sure that it is easier, cheaper and quicker to just bore out/sleeve crank halves(very simple procedure anybody with a lathe can do) and use readily available parts. Rod width and pin length can be easly modify by anybody with basic turning skills. Also labour cost in Australia is astronomical for making such parts so it does not matter what material you are going to use.
To make one pin would be quite expensive, the heat treatment alone would be the $80 minimum charge. That is why I was going to do a small batch of around 10 which would still be $80 for heat treatment of the 10. Material costs would be under $10 per pin and all the machining and grinding I can do in house, I not going to commit to a price until they are made but I think it will be economical for those bikes that no longer have a good source, are very expensive or can't easily be converted.
As for the machining out of the wheels to larger size I will agree with you that it is not difficult but I will ask you have done it yourself and are speaking from experience. I have done a lot off cranks that way but I have seen several others that claimed to be qualified machinists stuff good crank and put them in the bin as it is does require very precise work and as you said labour costs are very high.
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Agree. I made a jig that allows me to turn crank halves in a lathe. I usualy set from the original crank pin hole and make sure everything is sqare. Jig has a few treaded holes that are use to bolt crank halves and some counter weight on so when i spin the half crank it does not vibrates. Than carefully machine crank pin hole to make sure it has corect size. Also sometime reces in half crank needs to be opened up a bit to acomodate larger diameter thrust washers and big end. If the rod is wider than I either skim a bit of half crank face where the thrust washer sits, make thinner thrust washers or skim rod ends. I also have a jig that alows me to clamp rod on and skim faces on big or small end. Always make sure that everything is sqare before start machining. It is time consuming but i enjoy it. It can all be done on decent size lathe. No milling machine reqired. Also crank shaft needs to be balanced after doing this since new parts may have diferent weight to original parts.
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I'd love to see some photos of that jig.
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I have a fixture for machining the crank wheels that sounds a lot simpler that Thomas's setup but it is top secret. I'd be happy to show you if you are ever is Brisbane.
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I'd love to see some photos of that jig.
Not much to it Nathan. It is a 70 mm tall slice of old hydraulic cylinder with 30 mm thick steel plate of 200mm in diameter welded on it turned round and sqare plus some holes in it to set up and bolt half crank and some weights on. You seem to be curious but i am not going to tell you any more. You work out your own way of how to do this. I used very short boring bar to minimise vibrations when machining crank pin hole.
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I'd love to see some photos of that jig.
Not much to it Nathan. It is a 70 mm tall slice of old hydraulic cylinder with 30 mm thick steel plate of 200mm in diameter welded on it turned round and sqare plus some holes in it to set up and bolt half crank and some weights on. You seem to be curious but i am not going to tell you any more. You work out your own way of how to do this. I used very short boring bar to minimise vibrations when machining crank pin hole.
Possibly a bit more agricultural/requiring more skill than I'd hoped.
Anything to do with machining, always makes me feel like I'm hopelessly inadequate - despite how my skills have improved, I still feel just as inadequate as I did ten years ago.
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I'd love to see some photos of that jig.
Not much to it Nathan. It is a 70 mm tall slice of old hydraulic cylinder with 30 mm thick steel plate of 200mm in diameter welded on it turned round and sqare plus some holes in it to set up and bolt half crank and some weights on. You seem to be curious but i am not going to tell you any more. You work out your own way of how to do this. I used very short boring bar to minimise vibrations when machining crank pin hole.
That's way more complex than what I use. How long does it take to set up a wheel?
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(http://i1378.photobucket.com/albums/ah84/msfracingcomponentsmus/001_zpsktfwy0cy.jpg?t=1457015089)
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I have a jig that I machined years ago to hold Maico crankshaft halves. It is very simple to setup with a dial indicator in the 4 jaw chuck and I use it to machine 1mm off the inside of each flywheel half at the big end hole. This allows me to use cheap and easy to obtain Yamaha rod kits instead of the expensive limited life OEM ones. I've done a number of these and never had to rebalance the cranks. Perhaps the mass stays pretty much the same as the reduction in crank material is compensated for by the increased width of the big end bearing and journal.
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I'd love to see some photos of that jig.
Not much to it Nathan. It is a 70 mm tall slice of old hydraulic cylinder with 30 mm thick steel plate of 200mm in diameter welded on it turned round and sqare plus some holes in it to set up and bolt half crank and some weights on. You seem to be curious but i am not going to tell you any more. You work out your own way of how to do this. I used very short boring bar to minimise vibrations when machining crank pin hole.
[/quot
That's way more complex than what I use. How long does it take to set up a wheel?
Not long since my one was drilled for rm 125 crank the ofcentre hole is 25mmOD so i use a sleve to do the right half crank. once bolted to jig i just pop it in chuck and clock faces, ID and OD to make sure everything is sqare.
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(http://i1378.photobucket.com/albums/ah84/msfracingcomponentsmus/001_zpsktfwy0cy.jpg?t=1457015089)
You not suposed to give away secrets >:(
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It's a secret of common sense Tomas and probably unlikely to upset any commercial undertakings using a similar method.
I posted that for Nathan S to see: he is in my opinion particularly generous with helpful information and had asked.
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well its good to share ideas with fellow vmx's and gives me an idea for making holes in things i dont have big enough drill bits for or even abig enough drill press to take them if i had the drill bits and easy to tweak the chuck to line up the hole ;)another job to make up at the fitting course i do at tafe
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Thanks Momus. :)
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I was only joking Momus. It is a prety easy set up to work out even if you have never done such thing before. Happy machining.