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Buell Forum » Big, Bad & Dirty (Buell XB12X Ulysses Adventure Board) » BB&D Archives » Archive through August 22, 2011 » Empirical, unbiased vindication of Buell belt tension wheel « Previous Next »

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Electraglider_1997
Posted on Tuesday, August 16, 2011 - 11:13 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

By chance found this website. Remember that Harley utilized Buell's idler wheel concept only because it works as intended.

http://mysite.verizon.net/vze6wmx4/id106.html
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Prowler
Posted on Tuesday, August 16, 2011 - 12:15 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

As noted:
"if one sets the drive belt deflection at 3/8" (within the HD spec for belt tension)"

My belt as delivered, was drum tight and I was lucky to be able to flex it 1/8" by pushing on it midway between pulleys using the "official" H-D tool......and bottoming it out (left over from my Sportster days). Like I mentioned before, way too tight IMO, and it stays tight throughout the range of swingarm motion. If in fact there was 3/8" movement available between the pulleys (as delivered), I never would have felt it necessary to get the FS tensioner.
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Paul56
Posted on Wednesday, August 17, 2011 - 12:44 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Way back in 05 when the Uly was introduced and I was reading everything I could on it I seem to remember an explanation about the idler on some part of the Buell website. It said that engineers used some fancy software to locate the idler in such a position as to keep the length of the route within 3/8" from full suspension compression to full extension. Wish there was a way to retrieve old webpages like that.
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Froggy
Posted on Wednesday, August 17, 2011 - 12:47 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)


quote:

. Wish there was a way to retrieve old webpages like that.




Once something is on the internet, it cannot ever be totally eliminated. : )
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Froggy
Posted on Wednesday, August 17, 2011 - 12:54 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Found it, looks like it was a video, going to have to dig deeper to get that



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Trojan
Posted on Friday, August 19, 2011 - 07:45 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The ONLY way to keep belt or chain tension constant is to locate the swingarm pivot in exactly the same location as the front sprocket/pulley. The further you put the pulley from the swingarm pivot themore tension will change with suspension movement.
If anyone works out a way to do this differently without complicated linkages etc they will become a very rich man indeed!

Now take a look at the distance between the two on your XB and tell me how belt tension can be constant throughout suspension movement using a fixed tensioner pulley??

It said that engineers used some fancy software to locate the idler in such a position as to keep the length of the route within 3/8" from full suspension compression to full extension.

Software works out theoretical benefits but doesn't always work in practice ; )
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Blake
Posted on Friday, August 19, 2011 - 08:29 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The pulley maintains belt path length to within mere thousandths of an inch, not 3/8". This issue was discussed on BadWeB very recently. There's a Fuell article that addresses it.

It may be valid to argue that belt tension is excessive. It's not accurate to state that it varies significantly with swingarm travel. It doesn't.
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Blake
Posted on Friday, August 19, 2011 - 09:21 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Prior discussion with links to Fuell article.

To summarize, the idler pulley maintains total belt path length to within +/- 0.004".
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Blake
Posted on Friday, August 19, 2011 - 09:43 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

>>> It said that engineers used some fancy software to locate the idler in such a position as to keep the length of the route within 3/8" from full suspension compression to full extension.

No fancy software needed, just some intelligent programming. It's not anything that engineers all over the world don't do on a daily basis. The software just made it quicker and easier for the smart folks at Buell. Design optimization. The equations governing the geometry are fairly simple. The trick is to iterate and converge on a pulley size and location (total of three variables) that minimize the change in belt path length over the full suspension travel.

An Excel spreadsheet or most any good parametric design software in the hands of a smart engineer can accomplish the same.

>>> Software works out theoretical benefits but doesn't always work in practice.

Matt, the software simply helped them figure out where to put the pulley to minimize the change in total belt path length for full suspension travel. It was nothing more than a very straight forward analysis of geometry. No theory, just math and geometry. The software just allowed them to perform that analysis very quickly.
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Scooter808484
Posted on Friday, August 19, 2011 - 03:30 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Now take a look at the distance between the two on your XB and tell me how belt tension can be constant throughout suspension movement using a fixed tensioner pulley??

As the rear wheel travels upwards, the distance from rear wheel pivot to pulley center get longer which would cause increased tension. However, this is compensated for by less belt wrap around the idler pulley. Not too difficult to see how clever selection of pivot locations, idler diameter, etc. could have this compensation be nearly exact.
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Eulysses
Posted on Friday, August 19, 2011 - 04:00 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Yeah butt...(Scooter) that little wheel may release some tension in compression but adds it when the wheel falls out the bottom of the bike...getting air, pot holes etc. I see how the effort was made but there is something wrong when the long-legged ULY hits serious vibration (since my 09 was new) on dips two-up. Something not right. Not dialed in yet.
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Blake
Posted on Friday, August 19, 2011 - 04:18 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

This is the first I've heard of it George. I don't see it. Temperature and load can affect isolators. More vibes at shock compression could indicate a number of issues, or none at all. It's way too subjective and vague of a symptom to support a definite conclusion. It might just be harmless belt harmonics due to change in geometry. : )
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Blake
Posted on Sunday, August 21, 2011 - 10:56 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

With the bike on the sidestand and the rear suspension fully extended, I measured the deflection resulting from 10 LBs of applied force at mid-span of top run of belt on my 2009 Uly yesterday. It showed 3/8" deflection.

I then measured the bottom run, which is significantly shorter due to the idler pulley. It measured 5/16".

The belt did not seem overly tight to me at all.

That was on a room temperature bike. Will see if it tightens after running hard in the heat.
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Electraglider_1997
Posted on Sunday, August 21, 2011 - 11:25 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Blake,
I'd tend to believe that static tension values can be way, way lower than dynamic (running) tension values. A load cell on the idler would put this long running issue to rest but the chance of that taking place is remote. That 3/8ths to 5/16ths difference doesn't sound like much but when the rear wheel falls into a pot hole at speed it may mean one heck of a tension spike to the belt. My only belt failure at 25,000 miles happened on some pot holey road thankfully within 2 miles of home. I'm pretty pleased with the current setup, not perfect but beats the heck out of chain noise and maintenance. Installing a new belt on the side of the road could prove to be real cussing sweat inducer. That is why so many here pre-emptively install a new belt in their garage and keep the old belt under their seat as the spare.
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Danair
Posted on Sunday, August 21, 2011 - 12:07 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Mine broke yesterday at17k. Just got off freeway and put it in neutral at a long light. It popped when I put it back in gear. Looked down and saw belt on ground. Never even let out the clutch.
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Growl
Posted on Sunday, August 21, 2011 - 12:20 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

My belt broke at just over 25,000. At the time we were riding 2-up on a severe dirt road. The suspension was getting a full top to bottom workout at the moment it broke. When I put the new belt on I was careful to break it in with easy gentle riding for a couple hundred miles so that it could loosen up evenly.
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Blake
Posted on Sunday, August 21, 2011 - 12:25 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Running tension under acceleration or engine braking is going to be greater in whichever span of the belt is under load (top span for acceleration, bottom span for engine braking effect); that is a given.

The 3/8" versus 5/16" difference in deflection is due to the shorter span between rear sprocket and idler pulley versus the longer unbroken run between the two sprockets for the upper span of the belt, not that one is tighter. The bike was in neutral, so the drive sprocket was floating thus both spans were carrying the same tension. There is no physical factor that I can identify that would cause increased belt tension for the pot hole scenario you mention. I just don't see it.

I also checked two other XBikes yesterday by twanging and pushing on the belts. They felt the same as the one on my Uly.

Changing a belt roadside doesn't seem like much trouble to me. Loosen the rear axle, remove the guards and swingarm section, install new belt, button it all back up and go. What's so daunting about that? It is sure a heck of a lot easier than changing a tire roadside! Probably easier than changing the rear spark plug too. : D

One thing that folks are neglecting is the affect of less than optimal tension on the belt's teeth. The compliance of a looser belt may allow better survival if/when debris gets caught between belt and sprocket, but it may put a heck of a lot more stress on the root of the belt's teeth.

I'm not concerned with belt durability. I'm convinced it is excellent, especially with the newest versions and the requisite guards installed. I am concerned about the rear wheel bearing. I've not invested in the 2010 triple bearing rear wheel. I'm stubborn that way though. I think a single bearing should be sufficient. I will be checking and regreasing if needed when the rear tires is changed.

Jim Dugger found some fancy grease and some fancy bearings that he thinks will improve bearing durability.

That said, a spare rear wheel is not a bad thing either, as long as it includes it's own rear brake and sprocket too. : )
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Danair
Posted on Sunday, August 21, 2011 - 12:44 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

If you had seen my wheel after a bearing failure at 80 on the freeway, you'd be getting the newer wheel. Not counting the WTF pucker factor of the bike going sideways in traffic, by the time I got off to the shoulder, the bearing frags had destroyed the wheel where the bearing sits and cut the spacer in two. It seems its not a matter of if but when, and three bills and change for a whole new setup is cheap insurance and priceless peace of mind.

My .02
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Nobuell
Posted on Sunday, August 21, 2011 - 07:13 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

From what I have been reading, I believe the belt does maintain a relatively constant tension throughout the wheel stroke with the static tensioner. The issue as I see it not the functionality of the static tensioner but the high tension of the belt on some bikes. As previously discussed, when installing my new 2010 wheel and new belt, the tension was extremely high. So high in fact, I exceeded my 100 lb load cell to achieve my target tension. Contrary to a previous poster's comment, I did not hack away at the bolt hole but actually slightly slotted the hole to relieve the belt tension.

I cannot comment on the long term functionality of the Trojan Tensioner. I do believe that at least one thing the tensioner does do is eliminate over tensioned belts.

I still believe that there is a stack up in tolerance that can allow a belt to be overly tight. The XR1200 article did show that that a small amount of axle adjust (0.15") would drastically change the overall belt tension. Somebody would have a hard time convincing me that a 0.15" variance between the axle and sprocket centerlines cannot occur considering the motor is rubber mounted, the swing arm pivots on the motor and there are quite a few components ultimately holding the motor in position. There must also be some variances in the belt length.

It is interesting to me that HD thought it was necessary to have axle adjustment, thus belt tension adjustment even though they are using a similar static tensioner.

Quite possibly, Buell should have provided a method of belt tension adjustment to compliment the design of the static tensioner.
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Blake
Posted on Sunday, August 21, 2011 - 10:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

A cam at one of the tensioner bolts like you see used on adjustable swingarms on race bikes would allow easy adjustment of the tensioner pulley. Hmmm... : )
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Skinstains
Posted on Monday, August 22, 2011 - 12:24 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The belt is at it's tightest when the axle, swingarm pivot and trans sprocket are in alignment. (Fact)

Moving an axle .015 takes the .015 out of both runs of the chain so it must be doubled to be .030 (Fact)

I have converted my XB's to chain drives as I believe that the belt simply isn't up to the task. I also believe that it puts excessive tension on the rear wheel bearings as well as the output shaft's bearing & seal and the engine case where the idler bolts to it. (opinion)

On the bikes that I have converted to chain without installing a movable axle swingarm. I can only use certain sized sprockets and ratios as having the adjustment only on one chain run just isn't sufficient to allow all ratio combinations, even using half links. (Fact)

The belt on my 09 X was trying to pull my axle forward and output shaft rearward so bad that I didn't trust it at all. You could feel it trying to rip the bike apart, especially two up. (Fact/opinion)

I also think that it's a bunch of hooey that the belt path doesn't change more than 0.008" during the suspensions range of motion. I don't even think that they can keep that +/- 0.004" tolerance in manufacturing the belts. (Opinion)

It would be real easy to calculate if the distances between all three axes as well the diameter of all three pulleys was known. (Fact)

I won't try to figure it out because I don't have any of the pulleys to measure and it's just not that important to me as I know that all of my wheelbearings seem to last and last and last... (Fact)
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