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camchain tensioner spring

Taffy

Taffy

Joined Nov 2001
17K Posts | 774+
Ely, England
now here is a subject that we may not have touched on before!

just how much pressure is being put on the back of the tensioner blade?

sparks has chopped some off and feels sure that this is part of the problem in chain wear! so sparks and i talked of how it could be measured

remove sidecover
hold base of tensioner blade as is for when the tension comes off
remove the end nut and release the spring
measure with the heel of a vernier down to the back of the blade
do maths to the bottom of the nut and work out the tensioned length of the spring
set the spring up so that it can be measured what force is needed to get the spring back down to it's recently compressed state

find out what a "reasonable" pressure would be for another bike?

chop old spring about to get to new figure.

SO WHAT DO Y' ALL THINK?

some of you may recall the cambelt driven ducati pantah. well i raced one for 14 years and i had no covers on the belts. on revving the belt would quiver a little each side of the tensioning roller on the 'back run'. then on a closed throttle the 'front face' would quiver BADLY instead!!!!

the reason was because the 'pull' side had a roller that helped the belt stop quivering BUT BUT it also did it allowing the belt to have nearly a perfectly straight run!

i therefore suggest that the drive side of our chains is getting a bloody torrid time on a closed throttle and is probably quivering and fluttering around all over the show!!!!

should husaberg have had a curved stirrup on the drive side of the chain instead of that tube and nothing at all?

what do other manufacturers do?

what do you reckon lads?

regards

Taffy
 
anyone got a KTM and know whether they have the same spring?

regards

Taffy
 
well i measured one up today. only five clicks out with the blob still on the end and the latest 820 tensioner. the spring is 50mm long and it was 18mm twixt back of blade and flush to housing entrance. add 2mm for the washer. the hole in the bolt brings the spring flush still with the entrance.

so a 50mm spring is compressed to 20mm.

who can measure the strength of the spring at that compression and also equate that to what IWS, DID, Regina etc want in pressure on their chains? anyone know a chain tech?

regards

Taffy
 
sorry to bump this but can anyone think of anyone into "chains" who can tell us what kind of pressure a stirrup should exert on a chain?

is tight good for wear?

should the drive side run in a straight tube or on the back of another slight curve?

Nm or LB per SI loading?

i tried DID japan and they didn't understand me!

regards

Taffy
 
Taffy said:
sorry to bump this but can anyone think of anyone into "chains" who can tell us what kind of pressure a stirrup should exert on a chain?

is tight good for wear?

should the drive side run in a straight tube or on the back of another slight curve?

Nm or LB per SI loading?

i tried DID japan and they didn't understand me!

regards

Taffy
Click to expand...

Quite a few bikes (DR500s, XL500s) etc used to just run mechanical CCTs that you just adjusted manually.

I imagine the attraction of the sprung/locking pawl type is that you never have to adjust it and a chain with no slop.

When you consider the strain a cam chain is under to actually turn a cam under rocker/ valve spring tension, I imagine the sprung adjuster loading on the chain pales into insignificance compared to this

Just my thoughts :)
 
yes but if a staffordshire bull is ripping your kid to bits your name had better be popeye!

the chain has got to be CONTAINED because those old conicals are ripping the cam back and forth.

there must be a mechanical website out there somewhere that talks of the forces exerted etc.

regards

Taffy
 
Taffy,

If you're looking for the force the spring is exerting at a given compression distance, then you're looking for F=-kx, where k is the spring constant and x is the compressed (or stretched) distance. SI units for k is N/m, or in this instance you can use N/mm. You'll need a scale to measure force applied by the spring when you compress it to a given distance. Since k is linear, you can calculate the k value for the spring.

Hope that helps.

Jason
 
well it helps thanks but i want to know is it too strong? as i say 50mm crushed to 20mm. is that really that good? and now i have a lighter valve train i want to know if i can take advantage?

i suppose i could snip a bit of the spring off at a time but i won't see the 'flutter' of the chain on the accel/decel change and vice versa!

what YOU don't see is the cam chain when the drive reverses!

there must be summink on the web?

regards

Taffy
 
kzoo said:
As for a website explaining forces etc... have you tried http://hyperphysics.phy-astr.gsu.edu ?
Click to expand...

Taffy as you know I have cut a big lump off mine tensioner spring to no adverse affect. Now done over 1000 Miles since I did this with no cam chain noise at all.
This tensioner is obviously used on other engines and has to be bought complete, so it up to the manufactures of the engine to make it fit and give it the right stand off to give a reasonable tension pressure.
I presume most people on here have worked on jap engines and how many of you when you have come to fit the cam tensioner the spring is not nearly coil bound unlike on the Husaberg.
The spring is not there to stop the tensioner from going back, if the racket failed the pressure of the chain would push it back anyway.
As long there is enough pressure to push tensione arm it in the direction it is supposed to go then that is enough, hence that is why I decided to give the spring a severe hair cut.
In my estimation there is to much pressure being applied to the tensioner blade and I am wondering if this is contributing to premature cam chain wear.As long as the spring tension is great enough to take the tensioner arm to it-s up most then that will do.
It-s not a case of putting the chain under pressure but just taking up unwanted slack as we did with the manual adjusters.
The tension on the chain is on the front side not the tensioner blade side.
Some people may disagree but I think most will see what I am getting at.

Hell that was marathon and not even on a full glass of wine.

Regards

Sparks.
 
kzoo said:
As for a website explaining forces etc... have you tried http://hyperphysics.phy-astr.gsu.edu ?
Click to expand...

Taffy as you know I have cut a big lump off mine tensioner spring to no adverse affect. Now done over 1000 Miles since I did this with no cam chain noise at all.
This tensioner is obviously used on other engines and has to be bought complete, so it up to the manufactures of the engine to make it fit and give it the right stand off to give a reasonable tension pressure.
I presume most people on here have worked on jap engines and how many of you when you have come to fit the cam tensioner the spring is not nearly coil bound unlike on the Husaberg.
The spring is not there to stop the tensioner from going back, if the racket failed the pressure of the chain would push it back anyway.
As long there is enough pressure to push tensione arm it in the direction it is supposed to go then that is enough, hence that is why I decided to give the spring a severe hair cut.
In my estimation there is to much pressure being applied to the tensioner blade and I am wondering if this is contributing to premature cam chain wear.As long as the spring tension is great enough to take the tensioner arm to it-s up most then that will do.
It-s not a case of putting the chain under pressure but just taking up unwanted slack as we did with the manual adjusters.
The tension on the chain is on the front side not the tensioner blade side.
Some people may disagree but I think most will see what I am getting at.

Hell that was marathon and not even on a full glass of wine.

Regards

Sparks.
 
you're pissed or i'm seeing double!!!!!

so how much did you take off sparks?

my point would be this? that the tensioners are normally a lot longer and all just to give the spring room IMHO. after all if a spring is 70mm long and it presses up to 50 and then opens say 15mm to 65 of it's 70mm it will used a smaller percentage of it's preloaded state than a cpring that starts at 50mm, crushes to 20mm and opens again to 30mm.

whaqt would be interesting would be to find someone with a shagged chain. you know this because you pull the tensioner out the back and all the teeth are showing: it's at full extension. so you count the teeth but turn it back to zero. chop say, 50% of the spring off and refit.

start the engine, go for a spin and then pull it out.

did the tensioner use the same amount of teeth?

you could continue this experiment by clipping a helix a full 360 of coil off and going for a little spin till in the end not all the clickers were used.

now i do have a sins box with all my sins in it. and in the bottom is my first marzipan chain......

oh and after a search i noticed that manufacturers don't make curved tension faces at all. i suppose the cam timing could change. so the only thing they might do is fit a sprocket roller where cambelts have a sealed ball-race etc etc.

mmmm! i knew this would be interesting in the end. just had to drag it outta y'all as usual!

regards

Taffy
 
You could lessen the amount of cam chain tension by simply counting the clicks as you cram the tensioner spring in, then reset the tensioner but this time stop one or two clicks before full normal extension and then remove and don't use the spring. As Sparks stated its the ratchet that keeps the tensioner extended and not the spring.
You would need to check the tension periodically perhaps every 20 hours or so.
 
has anyone else had one of those spiral tensioners like i had on my SR500's (had 2)? you turned a screw and a spiral tensioner rolled all the way out and in with like just half-a-turn of the screw. and the thing was so, so, so LIGHT!!!!!!

definately always take the alloy 'blob' off.

when sparks tells us how much spring he has kleft we can conytinue. can't we steven!

PS. ne need to pull the exhaust.

PPS i will resurrect the tensioner blade/stirrup thread tomorrow as i'm not happy at this 'straight' takes the 'banana' thing!

regards

Taffy
 
husabutt said:
You could lessen the amount of cam chain tension by simply counting the clicks as you cram the tensioner spring in, then reset the tensioner but this time stop one or two clicks before full normal extension and then remove and don't use the spring. As Sparks stated its the ratchet that keeps the tensioner extended and not the spring.
You would need to check the tension periodically perhaps every 20 hours or so.
Click to expand...

another way......

how about holding as much spring in your fingers as it takes to get the tensioner go to it's last click? i did this and i held 20mm of the 50mm.

regards

Taffy
 
Taffy said:
husabutt said:
You could lessen the amount of cam chain tension by simply counting the clicks as you cram the tensioner spring in, then reset the tensioner but this time stop one or two clicks before full normal extension and then remove and don't use the spring. As Sparks stated its the ratchet that keeps the tensioner extended and not the spring.
You would need to check the tension periodically perhaps every 20 hours or so.
Click to expand...

another way......

how about holding as much spring in your fingers as it takes to get the tensioner go to it's last click? i did this and i held 20mm of the 50mm.

regards

Taffy
Click to expand...

Without having to rip off the exhaust of which I have finally got a good seal, what I did was how you have just explained, it pushed the spring so it goes through all the adjustment clicks I left about 10mm sticking out of the adjuster and clipped off the rest, so if you do that then you will know how long my spring is.
I am going to run it for another 1000 miles or so then remove the adjuster to see how much of the tensioner has been used if any.
This will bring the total mileage with this mod to around 3500 Miles.

Don't you all think that this engine is stressed out enough so by easing the stress I have fitted softer dual springs a more rounded profile cam (X2) and reduced the cam chain tension, it's all got to be going in the right direction!!!!, I hope.

Regards

Sparks.
 
you know, having thought about this more, i cannot see how on earth that this spring in it's present form should be allowed anywhere near the bike?

some people leave the alloy nob on as well and that means that virtually no teeth are used on the adjuster. i think the moment you get the fatter blade you should chop 10mm off. that should be a no ifs or buts must!

even with the nob off a 50mm spring was compressed to 12mm. that can't be right can it? having removed the spring first i removed the tensioner and tried to put it back and i really had to work hard at getting the faces to mate before starting a screw. it was easier to start one with the CCT still away from the back of the cylinder.

the pressure on the chain must be enormous?

anyway, it's now 30mm long.

regards

Taffy
 
Taffy said:
you know, having thought about this more, i cannot see how on earth that this spring in it's present form should be allowed anywhere near the bike?

some people leave the alloy nob on as well and that means that virtually no teeth are used on the adjuster. i think the moment you get the fatter blade you should chop 10mm off. that should be a no ifs or buts must!

even with the nob off a 50mm spring was compressed to 12mm. that can't be right can it? having removed the spring first i removed the tensioner and tried to put it back and i really had to work hard at getting the faces to mate before starting a screw. it was easier to start one with the CCT still away from the back of the cylinder.

the pressure on the chain must be enormous?

anyway, it's now 30mm long.

regards

Taffy
Click to expand...
Yeah go for it Taffy, I think mine was some where around 30mm. I think we can class our selves as guineapigs.
Still no adverse affects from shortening mine, must admit from when I first heard the engine in it's original state to what it sounds like now there's no comparison, the only noise that stands out now is the straight cut gears from the clutch basket and drive pinion, but your never going to solve that one.

Regards

Sparks.
 

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