Belt Tension and Vibration

[phj]

I've worked with belt drives and idler systems for a number of years and I've seen perfectly adjusted systems do horrible things to idler tensioning systems.
One of the problems is that you can pre-load the idler to deflect the belt statically but once the drive is running the "slack" side of the belt leaves the idler behind. When one side of the pulley is exerting force enough to stretch the belt, the other side becomes loose enough so that the belt will rarely touch the idler.
It's not a question of how much pre-tension is introduced into the system by the idler, but the resistance of the idler to be deflected by the belt vibrations.
It comes down to the choice of spring rate in the idler system. the length of the lever arm and the weight of the idler itself. A light idler will be easier deflected than a heavier one......too light of a spring rate will cause the idler and it's lever arm to flutter even against the spring.
If some means could be found to dampen those extraordinary belt excursions.........
Has anyone actually seen with their own eyes just what happens with a Spyder drive belt under load...??...Just look at your belt guard and see the marks.
Let me be absolutely clear here: I am in no way trying to malign the work already done by our SpyderLover sponsor in his business....I'm just trying to evoke further comments and suggestions.

I my case it (tensioner) has helped a lot but not completely curred the problem. I have tried every rpm/shifting combination and at higher speeds it just does not go away, lower speeds, less than 55mph any gear at any rpm it's smooth as silk. In my opinion the belt is just to loose and I am trying to get my dealer to go back to 750/800 newtons. They are reluctant because of BRP. I firmly believe that if the riders that are reporting no vibration checked their belts they would be much tighter than the 400 +/- 150 being called for by BRP

[Jeriatric]

I my case it (tensioner) has helped a lot but not completely curred the problem. I have tried every rpm/shifting combination and at higher speeds it just does not go away, lower speeds, less than 55mph any gear at any rpm it's smooth as silk. In my opinion the belt is just to loose and I am trying to get my dealer to go back to 750/800 newtons. They are reluctant because of BRP. I firmly believe that if the riders that are reporting no vibration checked their belts they would be much tighter than the 400 +/- 150 being called for by BRP

Higher speeds?

How high, and what RPM.

[Fire Bike]

I noticed some vibes on my new 2012 RTS but thought it may be normal after 30+ years on Goldwings.

[phj]

Hey Capt. Jim,

It was nice chatting with you again today. I had a great ride north today and did a lot more checking and what I found was that about 4550 rpms or 62/63 mph is where the vibrations now began (so it's getting better). If I am accelerating up in speed, the vibration continues and will not go away; however, if I accelerate to a higher speed and then slow to that 4550 rpms, there is no vibration and will run smooth until I start increasing rpms again. So, I believe we are very close and I look forward to the response you get from your engineers and maybe we can solve this once and for all.

As we also discussed, I did some high rpm shifting and it actually makes it vibrate more. But whether I'm in fourth or fifth gear at any rpm up to 61mph and 4500 rpms it is now smooth as silk and for other than road bumps you wouldn't even know the bike/engine was running. I also agree that some of what I may be feeling at the higher rpms may be coming from the engine for at the higher rpms you can feel the engine more, but I still have some belt vibration in there as well. If BRP would allow my dealer to reset the belt to 700 newtons I am sure that would along with your tensioner solve all the vibrations, at least on this bike.

Thanks again for all your advice and help, you are a true professional and build/sell a great product.

Paul

[summerdawn]

This is an interesting thread. I just returned from my first extended trip that included a lot of time at interstate speeds 65 to 75 mph. I found that as I reached about 73 mph (occasionally 71) there was a vibration/rubbing sensation in the bike. Going slower or faster got rid of it but it would come back at that speed. I was in 5th gear. Lower speeds are all smooth. After reading the thread I'm worried that if I ask the dealer to look at/adjust the belt I might wind up with more vibration.