Does anyone have experience with big singles in small alloy frames?

[koba]

I got a mutt off trademe! Cheap!

I dont mean to dribble but I think its the only way to explain my situation!

Its a Honda NSR250 frame and suspension etc...
But has a Kawasaki KLR600 single in it.:Punk: (check my profile for a pic.)

Its been pretty well built by someone (anyone know who?)

Its not all that fast but is basically a stock motor so there is a bit of potential there but considering my budget its probably just going to have to live with being slow! In its favour it has amazing cornering ability, although until I have a lot more race Km's behind me that wont matter much.

Anyway I was going to make a point!

Im aware there are a few of these type of things out there,
a couple of guys I was yakking to at my only time out on it at manfield had their own, one a RG/DR and i forget the other..

Unfortunatley i didn't then know I should ask them about engine mounting and vibration and if they could share their (probably secret) knowledge with me!

As far as I understand it a Vtwin (original motor) vibrates completley differently to a single and need to be mounted accordingly.
I have a plan in my head to add bits into the frame based on brainpicking I've done but wanted to get some feedback from as many people as possible, especially anyone who may have experience in this type of bike!

Any help greatly apreciated!
:done:

[Motu]

It will have a balance shaft and should be reasonably smooth.Are you sure it's a KLR600? They are pretty old,rare,and have problems.A better bet would be the much more popular and reliable KLR650.

[tri boy]

I mucked around with a Yam TT500 in an early RG250 frame.
It suffered from some cracks front and rear mount areas. But to be fair, I didn't spend much time perfecting the mounting system. Was a hoot to ride.:yes:

[koba]

haha yeah there is the catch..

KLR 600 so eligible for postclassic juniour.
It was made with balance shafts....
They are gone now...
Previous owner spent thousands getting them ripped out and having it balanced differently (I don't understand why..?)
He said it was unridabley vibratory (Engrish!) when he got it and that it improved when the work was done.
Maybe it was because it was known to have balance shaft probs..?
It is ridable as it is - just - but It cracked the (thin and inadaquate anyway) top engine mount - on the back of the head. Thats the main prob really, so I want to brace it differently but Im not convinced I know quite enough about what im doing yet...

[Sketchy_Racer]

Oh so many theorys on this.

Personally, the best i have seen, and seen the difference, is a mild steel 'subframe' for the motor.

teel is a far more flexible material than ally. it absorbs vibration a LOT better than ally.

Then there are theorys about putting sand in the frame etc etc... but those are just rumors i have heard.

Good luck i know that bike, and may be able to get some info about it for you

-Glen

[koba]

I mucked around with a Yam TT500 in an early RG250 frame.
It suffered from some cracks front and rear mount areas. But to be fair, I didn't spend much time perfecting the mounting system. Was a hoot to ride.:yes:

Anything you would have done to change the mounts?

[koba]

Oh so many theorys on this.

Personally, the best i have seen, and seen the difference, is a mild steel 'subframe' for the motor.

teel is a far more flexible material than ally. it absorbs vibration a LOT better than ally.

Then there are theorys about putting sand in the frame etc etc... but those are just rumors i have heard.

Good luck i know that bike, and may be able to get some info about it for you

-Glen


Cheers my current plan is pretty much that.
7/8in steel tube with squashed ends from the front hanging mounts to the to rear subframe mounts initially followed by somthing more permanent if it has a positive effect.
Judging by the marks on the fucked mount The motor moves up and back so this tube should triangulate the frame and stop that hanging front mount from flexing up and back and rooting the head mount.
My big worry with that is if the rear subframe brackets can handle that plus my new head mount plus the rear subframe... thats a heluva lota shit for them little brackets to cope with!

[Sketchy_Racer]

Cool as... 7/8in tube.. comon man!! were not in the states.. ;)

I would probably reccomend some 25mm X 2mm thick Box tube.

And cutting some 'v's into the ends and welding them shut to get the flats to bolt onto the ally frame..

at a guess...

[tri boy]

Different compounds of rubber would have been one option. (and quite cheap)
Bracing suspect areas. Also Briggs and Stratton used to have a rpm tool for there stationary engines that would assist in locating frequency vibrations.
Talk to a mower shop. One of the mechanics may have one.

[koba]

Cheers guys.
I've still gotta talk to the original owner to see what info I can get on the balancing work done so i may be able to find the exact angle of vibration (so Im told!?)

Guess I will suck it and see anyway. hehe my neigbours love me!

Got lotsa bits n pieces to do on it yet but its a good mental exercise!
Learning HEAPS, any more comments, suggestions or whatever are more than welcome.

[riffer]

Hey dude,

not sure how much I can help but I'd love to come around and see this sucker!

PM me with your address details.

Simon

[cowpoos]

Cool as... 7/8in tube.. comon man!! were not in the states.. ;)

I would probably reccomend some 25mm X 2mm thick Box tube.

And cutting some 'v's into the ends and welding them shut to get the flats to bolt onto the ally frame..

at a guess...
yep...and seal the box and fill with sand if you can...will take away heaps of vibs!!

[koba]

yep...and seal the box and fill with sand if you can...will take away heaps of vibs!!

If its bolt on i can try both...

Keeping short with large cross section should help keep the resonant frequency thingy in a good range, I think! Its all a bit scientific for me...

Was It you who was bidding on it originally? (check my profile for a pic on it)

[cowpoos]

If its bolt on i can try both...

Keeping short with large cross section should help keep the resonant frequency thingy in a good range, I think! Its all a bit scientific for me...

Was It you who was bidding on it originally? (check my profile for a pic on it)
yep....I decided not to take it [it was offered to me after the auction never met reserve] after talking to him on the phone about it...he was honest about how quick it was...and I though it might have had more go that what he discribed...

[koba]

Yeah It doesn't exactly rip your arms off....

[pete376403]

One of my early speedway bikes used to vibrate like a dog shitting a length of chain. The engine bolts were tight, but the holes in the cases were worn due to having been run with bolts loose before I got it. I fixed a lot of the vibration by reaming the holes to be a close fit to oversize (ie next size up) bolts. Reamimg is more accurate than drilling. I also made a head steady that went from one of the cylinder head bolts to the frame junction under the seat. With the new bolts and the steady, while not smooth as such, I could at least ride it without my foot being vibrated off the footrest.

[roogazza]

Anything you would have done to change the mounts?

Hey bud , I was chatting to you at Manfeild ! My mate is the one with the RGV with the DR650 in it. I know his thing vibrates too, but hasn't suffered from any broken mounts as yet. He lock wires everything and uses Locktite, but still has to go over it after every outing.
Look for him at the winter series his name is Mark, No.176 I think ? Gaz.

[Coyote]

You can check out the RG and see how it's mighty single cylinder engine is mounted :lol:

Got me thinking about getting a big engine for the RG project now. A KX500 mill would be fun...

[koba]

One of my early speedway bikes used to vibrate like a dog shitting a length of chain. The engine bolts were tight, but the holes in the cases were worn due to having been run with bolts loose before I got it. I fixed a lot of the vibration by reaming the holes to be a close fit to oversize (ie next size up) bolts. Reamimg is more accurate than drilling. I also made a head steady that went from one of the cylinder head bolts to the frame junction under the seat. With the new bolts and the steady, while not smooth as such, I could at least ride it without my foot being vibrated off the footrest.

Your bloody well right! The top mount was suffering the most, obviously due partly to the bolt being way to small and not a fit and the frame not being braced right.
Fortunatley the softer bit thats been muched is in the mount I've introduced to my hacksaw friend!

[koba]

Hey bud , I was chatting to you at Manfeild ! My mate is the one with the RGV with the DR650 in it. I know his thing vibrates too, but hasn't suffered from any broken mounts as yet. He lock wires everything and uses Locktite, but still has to go over it after every outing.
Look for him at the winter series his name is Mark, No.176 I think ? Gaz.

Hey, hopfully I will see you guys back there in the near future!
Yeah LOTS of locktite! We soon found out which bolts had none on them...!
All this flucking around with mounting and bracing is just to keep the motor in the bloody frame without it shaking its way out!
Maybe his mounts are better built?
I guess Im going to have to get used to coming off the track a few fillings short of a smile :)
But what smile I do have is going to be very wide!

[Fooman]

teel is a far more flexible material than ally. it absorbs vibration a LOT better than ally.



Ouch, cannae let this one slide...

Steel, as a material is stiffer than alloy, by approximately 3 times. But because alloy is ~ 1/3 the density, you can have 3 times the material for a frame of the same weight, which can increase the overall rigidity.

Essentially rigidity = (some constant) * E (modulus of elasticity) times I (second moment of area of section resisting the bending force)

E for steel is ~ 210 GPa, E for Alloy is ~75 GPa

I is the area moment of inertia, and is a function of the distance perpendicular from from the centroid of the section cubed and/or the distance parallel to the centroid - a rod twice the diameter has 16 times the stiffness.

The problem with alloy frames is not really stiffness, but damping, and susceptibility to fatigue cracking. Alloy doesn't have the same inherent damping characteristics as steel, hence:



Then there are theorys about putting sand in the frame etc etc... but those are just rumors i have heard.


so, an underdamped alloy frame will vibrate at a higher amplitude and for longer than a steel frame (given the same input load). The vibration (repeated displacement) is translated into a repeated (cyclic) stress by the elastic stiffness (E) of the material.

Steels will not fail in fatigue if the cyclic stress is below a certain level. This level is affected by a number of factors - surface finish, stress ratio, material condition, but it is always there. So if the vibrations are low enough, the steel will not fatigue.

Alloy on the other hand, will always suffer from fatigue, regardless of the stress level - the lower the stress, the longer it it last, but it will always fail.

So, having an alloy frame for a big vibey single is not ideal - the material characteristics of the frame means that the vibrations will be bigger, and the frame/mounts will eventually crack. This is generally not a problem in production bikes, as engines would be balanced, rubber mounted, and the frames would (should) be designed to last a few billion engine revolutions.

Glenn's suggestion of a sub-frame is a good one - but mount the single with rubber mounts in the sub-frame, and use the sub-frame as a stressed member in the alloy frame, if the engine was originally a stressed member.

Check out John Robinson's Motorcycle Tuning: Chassis book as it has some details on engine mounts.

Cheers,
FM

[avgas]

Ouch, cannae let this one slide...

Steel, as a material is stiffer than alloy, by approximately 3 times. But because alloy is ~ 1/3 the density, you can have 3 times the material for a frame of the same weight, which can increase the overall rigidity.

Essentially rigidity = (some constant) * E (modulus of elasticity) times I (second moment of area of section resisting the bending force)

E for steel is ~ 210 GPa, E for Alloy is ~75 GPa

I is the area moment of inertia, and is a function of the distance perpendicular from from the centroid of the section cubed and/or the distance parallel to the centroid - a rod twice the diameter has 16 times the stiffness.

The problem with alloy frames is not really stiffness, but damping, and susceptibility to fatigue cracking. Alloy doesn't have the same inherent damping characteristics as steel, hence:



so, an underdamped alloy frame will vibrate at a higher amplitude and for longer than a steel frame (given the same input load). The vibration (repeated displacement) is translated into a repeated (cyclic) stress by the elastic stiffness (E) of the material.

Steels will not fail in fatigue if the cyclic stress is below a certain level. This level is affected by a number of factors - surface finish, stress ratio, material condition, but it is always there. So if the vibrations are low enough, the steel will not fatigue.

Alloy on the other hand, will always suffer from fatigue, regardless of the stress level - the lower the stress, the longer it it last, but it will always fail.

So, having an alloy frame for a big vibey single is not ideal - the material characteristics of the frame means that the vibrations will be bigger, and the frame/mounts will eventually crack. This is generally not a problem in production bikes, as engines would be balanced, rubber mounted, and the frames would (should) be designed to last a few billion engine revolutions.

Glenn's suggestion of a sub-frame is a good one - but mount the single with rubber mounts in the sub-frame, and use the sub-frame as a stressed member in the alloy frame, if the engine was originally a stressed member.

Check out John Robinson's Motorcycle Tuning: Chassis book as it has some details on engine mounts.

Cheers,
FM
Fair enough.....except for annodising ;)
but i liked the fact that you mentioned that aluminium cracks. its why i still prefer cro-moly mountainbikes

[Fooman]

Fair enough.....except for annodising ;)
but i liked the fact that you mentioned that aluminium cracks. its why i still prefer cro-moly mountainbikes

Anodising doesn't really affect the physical properties of alloy (stiffness/damping). The layer of aluminium oxide is generally too thin. It will help protect from corrosion, which (sort of) increases fatigue resistance - corrosion pits can act as fatigue crack initiation points. But it won't affect general fatigue crack initiation from things like sub-surface flaws (e.g. oxide stringers or incoherent precipitates) or poor machining.

Cr-Mo-V steel framed pedaly here as well... :yes:

Cheers,
FM

[Ivan]

Hey bud , I was chatting to you at Manfeild ! My mate is the one with the RGV with the DR650 in it. I know his thing vibrates too, but hasn't suffered from any broken mounts as yet. He lock wires everything and uses Locktite, but still has to go over it after every outing.
Look for him at the winter series his name is Mark, No.176 I think ? Gaz.

I know the bike it was at tech last year

Black isnt it?

[roogazza]

I know the bike it was at tech last year

Black isnt it? Thats the one , its finally reliable now but the vibes persist. G.

[The Pastor]

Ouch, cannae let this one slide...

Steel, as a material is stiffer than alloy, by approximately 3 times. But because alloy is ~ 1/3 the density, you can have 3 times the material for a frame of the same weight, which can increase the overall rigidity.

Essentially rigidity = (some constant) * E (modulus of elasticity) times I (second moment of area of section resisting the bending force)

E for steel is ~ 210 GPa, E for Alloy is ~75 GPa

I is the area moment of inertia, and is a function of the distance perpendicular from from the centroid of the section cubed and/or the distance parallel to the centroid - a rod twice the diameter has 16 times the stiffness.

The problem with alloy frames is not really stiffness, but damping, and susceptibility to fatigue cracking. Alloy doesn't have the same inherent damping characteristics as steel, hence:



so, an underdamped alloy frame will vibrate at a higher amplitude and for longer than a steel frame (given the same input load). The vibration (repeated displacement) is translated into a repeated (cyclic) stress by the elastic stiffness (E) of the material.

Steels will not fail in fatigue if the cyclic stress is below a certain level. This level is affected by a number of factors - surface finish, stress ratio, material condition, but it is always there. So if the vibrations are low enough, the steel will not fatigue.

Alloy on the other hand, will always suffer from fatigue, regardless of the stress level - the lower the stress, the longer it it last, but it will always fail.

So, having an alloy frame for a big vibey single is not ideal - the material characteristics of the frame means that the vibrations will be bigger, and the frame/mounts will eventually crack. This is generally not a problem in production bikes, as engines would be balanced, rubber mounted, and the frames would (should) be designed to last a few billion engine revolutions.

Glenn's suggestion of a sub-frame is a good one - but mount the single with rubber mounts in the sub-frame, and use the sub-frame as a stressed member in the alloy frame, if the engine was originally a stressed member.

Check out John Robinson's Motorcycle Tuning: Chassis book as it has some details on engine mounts.

Cheers,
FM


Shit, Im learning about that shit at uni, Motorbikes ftw.

[koba]

Wow fooman!
Thats a lot to digest!
Thanks tho it is very useful info!
I really like the rubber mount subframe idea, however is probably a wee bit beyond my ability/budget at the moment.

Im buzzing with ideas on how to do such a thing but it may be somthing to do medium term with a temporary fix for now.
The bike Isn't going to be doing to many Kms this year so hopefully minimal use will mean minimal damage!

I have made up some braces out of the 7/8 tube (american sounding I know)

Didn't use inch square box (sorry 25mm box) because its just a fraction to tight between the frame and motorand im reluctant to hit the camchain tensioner with a file!

Also tube should also be better where im not 100 percent sure on which direction the major vides are moving? not sure on that but it seems logical.

Looking for the book fooman meantioned!

I've borrowed another book off a mate called "Motorcycle chassis design: the theory and practice" by Tony Foale and Vic Willoughby.

It is an excellent book and highly recomended, its not to technical so Its easy as to read yet still conveys bucketloads of knowledge.

[avgas]

Anodising doesn't really affect the physical properties of alloy (stiffness/damping).
Really? Thats quite interesting to hear as i have never had anything anodized fail on me :gob: Yet i seem to always have issues with everyother matierial failing around the anodised aluminum.
But it terms of dampning, anodising is a dog. I was tempted to put it on a few projects in Fonterra - but the vibrations coming off the lines made most earthquakes seem pathetic. Shame too - as it ment that the aluminium/steel guides that were put in didnt last more than 5 years. You keep building shit stronger and the monkeys keep finding ways to break it. Forklifts are a chassis worst enemy round a factory.

[The Pastor]

kinda a stupid thing, but if you fill it with sand, make sure you dry the sand out first..............:rockon:

[bumsex]

you are lucky that you no longer have the twin balancer shaft assembly. I had a klr600 recently which had shat the balancer shaft drive chain. The rear balancer chain I think also drives the oil pump, so the engine was a mess.

By the way I tried to find an aftermarket counter balancer drive chain to suit but could not find one anywhere. I ended up buying the original part from kawasaki for just over $400. yes, 400 bucks for a length of roller chain.

[cowpoos]

Then there are theorys about putting sand in the frame etc etc... but those are just rumors i have heard.



dry sand is a awesome vibration/noise damping tool....I doubt they are just rumours... shake an empty jar....then fill it full of sand and shake it!! beat ya its harder to shake ;)

[koba]

you are lucky that you no longer have the twin balancer shaft assembly. I had a klr600 recently which had shat the balancer shaft drive chain. The rear balancer chain I think also drives the oil pump, so the engine was a mess.

By the way I tried to find an aftermarket counter balancer drive chain to suit but could not find one anywhere. I ended up buying the original part from kawasaki for just over $400. yes, 400 bucks for a length of roller chain.

Maybe thats why mine has been removed....
Wouldn't be surprised!