OzVMX Forum
Clubroom => Competition => Topic started by: 211kawasaki on June 15, 2008, 07:09:12 pm
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Welcome to the new noise debate - a positive attempt to ditch the bullshit and get on with it. ;D
Tip # 1
The best start point on the path to reduce noise if to get a muffler, if your bike dosnt have one then it needs one. Even my AJS now sports a huge big chrome thing that looks like it should be there and drops a truck load off the DB. :)
Fatboy - its your domain, what about some wisdom.
211
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Spent most of the weekend fabricating a new exhausts system. Parts required to build muffler ( $25-00) shown
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what are you using for the baffle stew? it dont seem to have many holes/inch
anyone know a place to get rubber blocks for cylinder fins?
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Old inner tubes pokey.That core looks like it will need a few more 'oles Stew ;D
Another one is a core where the 2 ends a inserted diagonaly into the end can and the ends are past each other in a central chamber.I know I didn't explain that well but I'll get a better pic of it.
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Multi cylinder four stroke sidecar Easy!!!! Headers into 4in1 collector, then into car type small muffler/resonator, then short droopy tail piece directed at ground. ;) Make sure your have some sort of heat guard over hot bits for the passenger/swinger/monkey/fat ballast protection. Might be an idea to check your jetting after finishing noise abatement project too. Tim
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with 2 strokes, it all seems to be relative to the silencer.
i'd imagine a few of us will travel down the path of making our own, cause thats what we do.
is there any formula/theories in reguards to core diameter/length of silencer for size of engine?
keeping it simple for 2 strokes with this question.
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Hi all,
I agree with Dave lets just get on with it,
firstly even if your muffler is brand new pull it apart see how it is packed in my experiance mufflers staight from the factory are packet badly usely way too tight,I had bad noise problems with brand new pro circuit mufflers which went 106db on a modern KX85 the owner was going to send it back as the pipe and muffler cost $1200.00 each he had two bukes,but on closer examinatin we pulled it apart and it might not have been packed as the packing had been jambed in way too tight, we repacked it with some wool packing, not too tight or all the noise goes straight out the back not through the packing ,result 97.9 db which is a pass.
Second check your perfeated tube and drill out your holes as big as possible, uselly when they are new they are about one eighth, drill them out to about a quarter as big as you can do every hole repack again and you will notice the difference even on an old muffler.
If you are making a new muffler make it as big as you can, uselly two stroke mufflers are two short, most of the muffler is in behind the side panel and you dont even see it anyway The longer you make it the quieter it will be if you follow steps one and two as well.
four stroke bikes are the same except you can gain even more as much as 5 db by rapping the outside of the pipe with a suitable thermal rap,this is the cheapest and easiest way of making a four stroke queit.
I got my old XL350 from 114db down to 98.9 by doing every thing I listed above drill tube,repacking and rapping the pipe. Cost $80.00 and a bit of time it is really that easy.
Cheers
Fatboy
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my bits...
old grease gun case with thread cut off, piece of tubing from bench press accessory that I didn't want, couple of bits of sheetmetal hammered into cone shapes, and perforated sheet from old tv table rolled around a broom handle and welded up.
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Long aluminium silencers are better than steel or carbon fibre.
The stinger can be extended back into the body of the 2stroke expansion chamber.
Supertrap silencer rings can be added to the end of the alloy silencer to take the bite out of the sound.
Rubber plugs between the cylinder and head fins can take out the ringing.
Countershaft sprockets with the rubber lips to cushion the chain can reduce chain noise.
Thick rubber blocks inside the countershaft sprocket cover.
Can we wrap the exhaust pipe in something?
Should we be getting GMC to make us thicker walled pipes?
What other suggestions do you guys have?
The stinger before the muffler can be extended back into the body.
This has been used successfully in the past on bikes like the TZ750.
My TDR comes from the factory like this.
It does not reduce the power output but it does reduce the noise a lot.
For more detail see '10.16 Tailpipes' in 'The High-Performance Two-Stroke Engine' by Dr John C. Dixon. Haynes 2005.
Here are my suggestions from the Decibels thread.
I highly recommend Dixon's book.
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Sensational advice,
Fatboy, do we argue for the RPM limits as shown in the GCRs generally which will allow the reading to be at a lower RPM in vintage MX. For example 54mm bore TM125 will be 800 or so RPM less on this scale than the MX scale as used today. In effect you can have a louder TM125 if you race DT than MX if you go by the current situation. (yes folks there are different scales of measure but you will have to know bore and stroke).I suggest that the commission lobby on behalf of the riders to have the scale as used by Speedway, Trials, Dirt Track, Road Race etc etc etc and not be lobbed in with the same soup as modern MX.
I feel that its important that there be ways for the riders to reduce the noise of the bikes and I also feel that there is a responsibility of the commission to look for ways within the rule book that we can make the rule book work better for the VMX community.
We need to determine the basis for which modern MX made the RPM limit to DB, Modern MX bikes are very different to VMX and what they use to make their determination of RPM will not be a suitable rationale for VMX plain and simple. How did the Modern MX guys come up with their scale?
What do you think?
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Its worth a try to have vmx classed with the others and not with the moderns and the other suggestions
are helpful except that the rubber on the sprocket covers and on the sprockets would only help if the noise testing is done by the drive past method(ADR style).
Another source of noise is the induction into the engine,the quieter the muffler,the more this comes into play.
(http://i167.photobucket.com/albums/u125/mhplum/muffler.jpg)
this s/hand muffler from a 2001 YZ250F cost me $60 (was dented on inside) and the noise level tested at 99db,this could be reduced by replacing the packing,fitting supertrapp style end plates and or wrapping the header.
its appearance could be toned down by painting it flat black.
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IM curiuos to know if you put a pipe away from the motor to a farther point ( some kind of hooked up pipe section, what the actual noise of the motor contributes to a readiing on a meter at the perscribed distanc and position. SO like the exhuats exist from the front away from the bike and meter, but the meter is still in the same position and reads of the other background noise from the bike, id be curious as to how much impact or contribution to the final reading is actually made by things other than that exisiting out from the end pipe.
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Great idea Dave I think we should argue for the RPM limits as shown in the GCRs generally which will allow the reading to be at a lower RPM in vintage MX. The biggest advantage would be for big bore bikes but I think all bikes would be at a lower RPM, I did test a couple of bikes at Classic Dirt using this scale and it did make a bit of difference. This would work great as long as all riders new there bore size and I think that most riders know what size there piston is, the table in the GCRs is very easy to understand.
Please let us know what you think as Myself and Dave would be more than happy to lobby MA for us to use this scale instead of the modern MX RPM scale.
We as commissiners are here to work for you and I think this would be a much fairer way of measuring VMX bikes.
Cheers
FATBOY
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What about the 2 strokes ? mine seems to lighten off the cackle the higher it revs ? low down it sounds like a 4 stroker
im thinking a low rev would give my 2 smoker a worse reading ? then again i have no idea what its pumping now and wheather the meter hates the low gurgle or the higher crackle. still to my ear is sounds quieter the higher it revs ;)
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Tip of the day.
Mnaufacture or purchase a suitable silencer.
To easy
Time to move on now
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Tip of the day.
Mnaufacture or purchase a suitable silencer.
To easy
Time to move on now
Um what if that doesnt help husky61, try being a little more creative, this post is about getting a number lower than a cheap can fix. You actually need to think a bit more than that. ::)
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Shoeys 100% right Freaky. Move on. It's not rocket science to get your bikes under 96db. The first step is buying or making a decent muffler and the next step is fitting it to the bike. Da Da....Problem solved. Next problem please?
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Second and creative tip of the day.
Manufacture or purchase a suitable silencer.
Time to move on now
Rockets , Rockets are easy , silencers are even easier.
Its one option or the other , a little time / development to make your own or a little money to purchase one. Too easy
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YOur both really big on thinking i see. ::)
Its a pity DaveT went to all this effort to make this thread up to come up with some more creative thinking.
great...... top effort ::)
IF you cant be constructive stop being distructive.
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Wanker
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For fork sake Freaky, move on, we all have.
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Wanker
For fork sake Freaky, move on, we all have.
Great another top effort from you 2 morons.
Show sum respect for Dave who moved this thread here to get some fresh imput, iTs a constructive thread aimed at looking for new options as you 2 brain surgeons are out of new options please go to another thread, perhaps the old Db' thread where shit like this and lame " change you muffler posts' where plentiful.
We all did move on and came over here for a chat, but for some reason you Losers keep following us. and Gee how nice of you to decide when our threads can start and finish.
Go away FFS ::)
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I for one thought this thread was to share ideas on how to Quieten our bikes down not how to carry on about who writes what !
anyone that has ideas on silencers that save us a bob or two great, pictures even better cheers !!!
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My XT runs a left side pipe like an HL system or GMC pipe. There is a small muffler in the head pipe beside the cylinder but the tail pipe is larger in size than the head pipe and lined with a piece of perforated pipe.
This makes a big difference to just running a straight tail pipe.
This idea came from where I served my apprenticeship, they made tube and exhaust systems. As a trial they made some tube which was a perforated tube enclosed in a sound deadener (about 1-2mm thick and probably asbestos) with a normal tube over that. An exhaust system was made and fitted to a company car, this system had no mufflers or resonator and certainly didn't need any.
Dyno runs proved no difference in power but for various reasons it never went any further.
I've just read this post and was finding a few ideas only to find it's deteriorated into a slanging match..pity
Brent
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These DB Dawgs look simple and easy and cheap enough, if they take 10db off, that clears up at least 80% of bikes at a guess ;) doesnt really change the look of your bike a great deal either, has anybody ever tried or of anyone who has tried one of these
http://www.dirtwerkz.com/Pages/products/exhaust/dB_Dawg.html
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I have a new DG oval silencer but it may not be long enough.
Is there somewhere I can get some of that oval alloy tubing to make a longer silencer body?
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These DB Dawgs look simple and easy and cheap enough, if they take 10db off, that clears up at least 80% of bikes at a guess ;) doesnt really change the look of your bike a great deal either, has anybody ever tried or of anyone who has tried one of these
http://www.dirtwerkz.com/Pages/products/exhaust/dB_Dawg.html
be interesting to see if they actually work or could be made how can we say " similar " on a local inhouse level. interesting they say 4-6 db reduction but also refer to the AMA 99db rule
What about coatings ? as in you coat the pipe to absorb the sound waves ?
YEs im glad too this post has returned to reality brent. but dont speak to loudly they might return.
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These DB Dawgs look simple and easy and cheap enough, if they take 10db off, that clears up at least 80% of bikes at a guess ;) doesnt really change the look of your bike a great deal either, has anybody ever tried or of anyone who has tried one of these
http://www.dirtwerkz.com/Pages/products/exhaust/dB_Dawg.html
this product has been put on this ozvmx forum before,but no one has commented, maybe this time. :o
hey mainline did it work ???
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I don't know, the bike doesn't run yet ;D but I was pretty happy with the way it looks ;D ;D ;D
Seriously though, I used the dimensions of a stock muffler as a pattern. Mine is slightly longer and a bigger diameter, and so is the new muffler. boom tish.
Also, the core I've used has slightly bigger holes and I'll be using a decent muffler packing. The original mufflers were a one piece item and I made mine to be repackable, so fingers crossed.
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Attached is a diagram and explaination.
This is based on a couple of silencers that we have manufactured and tested on 250cc two strokes. The outcome has been quite successful and considerably lower cost that than after market brand type silencers.
Time to manufacture was approx. 2.5hrs from start to finish excluding the time taken to source the required materials
Note: The longer the silencer the greater the acoustic reduction. Some brands allow for the concealment of longer silencers.
I have written a presented a number of papers on acoustic reduction for industry application over the years and would be pleased to email parts of the papers for those who like to properly understand the principals of acoustic reduction Some of material is not particularly relevant to motor cycles but will provide an overview on the principles of acoustic movement and reduction.
Freakshow , you are still a wanker
Shoey
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Husky, thanks for that. Interesting point about not overpacking the muffler or wrapping the core too tightly, I'll bear that in mind.
Other than that my homemade jobby looks like it should work well based on your diagram.
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Thats OK
Dont forget the bend at the outlet of the silencer , this makes a considerable contribution to the noise reduction.
Remember , that with a 70% or greater free area used in the preforated silencer core(large perforations) ,maintenance is greater due to errosion of the absorptive material caused by the high velocity exhaust gases , prior to blocking of the perforations due the oil entrained in the exhaust gases although the blocking of the larger perforations takes considerably longer or conversely you can use 70% or greater free area with smaller perforations which will block quicker with less absorptive material errosion. Either way it still requires maintenance.
The larger perforations showed approx. 0.5dba greater noise reduction at 3.0m, which barely perceptable to the normal human ear.
Regular cleaning and repacking will overcome the above issues keeping the bike relatively quiete
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Attached is a diagram and explaination.
Freakshow , you are still a wanker
Shoey
pffft............ let me get you a Waaaaammbulance you sook :'(
at least you have finally pulled your head in and been constructive....... . Wasnt too hard was it ?
<<<< Talk to the hand :D
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Wanker
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husky61,
Thanks for posting the drawings, any advice for four strokes?
I'd be interested in the info on noise reduction you mentioned in your post if possible.
Brent
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Looza ... I have drilled the oles out to 6mm and added more of . 4 stroker ;)
The baffle is 50mm in dia OD (perferated section )with a stub taking it back to 44.5 mm
6 of 14 dia x 30mm long ( rocket launches ) welded in a group which fits inside the baffle.
The end cone is 80mm x 51mm , and overall length is 280 long
Bottom pic showing expanded end that baffle slips into ( 44mm ) inside
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Hey Old fart
That silencer looks the goods . I have noticed some of the performance pipes for larger capacity road bikes utilising this method.
Brent , i have a particularly good silencer on my HL , that has little or no effect on the performance of the engine. I didnt make this silencer but i will measure it and PM the detail
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Thanks Husky,
you going to Conondale this year? I want another race
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Hey Brent
We are going up to Connondale.
I will not be competing as Iam still recovering from a knee reconstruction , i will be taking my CR390 auto and will have a ride during the practice session on saturday.
See you there.
Cheers
Shoey