Belt Drive

Funny, people talk about belt final drive as if belts just fail, leaving people on the side of the road, all the time.

I must say that here in the states the vast majority of motorcycles on the road (except the sportbikes) are belt final drive. I have seen very few cases of belt failure. A couple were due to the belts being too tight, and there was a bad run of Goodyear/Falcon belts that made their way to consumers... those were snapping like rubber bands, but it was not a belt drive issue, it was a manufacturing issue.

Then again... the vast majority of bikes on the road are Harleys. Their 103" engine puts between 67 and 70 HP to the rear wheel and torque in the low 80s in ft-lbs... anything would work for that.

I have seen one Victory break a belt. It happened at the drag strip. Come to find out, the belt had never been replaced and the bike had over 50K miles on it. This happened in 2008 and the bike was built in 2001, so the belt was probably 8 years old. Tires expire in 1/2 that time.

I hope we are clearing up the 'short life' and 'ultimate strength' issues.

Ya know, I never worry about my belt. I heap abuse on it regularly, put BIG torque through it (twice the torque of the average sportbike), and rarely look at it unless I'm changing the rear tire. Been doing this since April 2007 and clocked probably 62K miles without issue. I'm pretty much convinced the belt is reliable.

The Buell 1125R belt has been on here for 3500-ish miles, replaced because the OEM belt was too long with the smaller-by-2-teeth countershaft pulley. This belt is 1/8" narrower than OEM. So far, so good. After the initial stretch and re-adjustment, I haven't touched it.

"It was jerry burgess"
... yes, he's got my yellow and blue kevlar belt. I don't know what his plans are for it, but somebody said they said a mechanic painting a yellow '46' on it. I think Rossi is going to use it to whiplash it at Jorge... if he can get close enough to him on track.

"Their 103" engine puts between 67 and 70 HP to the rear wheel and torque in the low 80s in ft-lbs... anything would work for that"
... most of the dyno charts I've seen show those figures for the twin cam 88's. The 96 was a bit more powerful and the charts I've seen for the stock 103 tends to be about 80 hp and up to 90 lb/ft. HD claim 100 lb.ft so 90 at the rear hoop seems credible.

That's still a very high torque figure compared to most big road bikes, but just like any cruiser, it's not going to be repeating that power very quickly, which is easier on the driveline.

If a sportsbike makes half the torque of your Victory, but revs twice as fast and high, which is under the most stress? Probably the sports bike, because it's generating more heat revolving twice as quickly?

It's important for us to remember that power is the repeatability torque. And that if we want more power we have to rev harder and have more cylinders. Twins don't produce more torque than fours for the same capacity if they have the same technical design. Instead, they produce more accessible power (a lower max power is achieved at lower revs), so they often 'feel' more powerfull to everyone not using max revs - such as a typical road user, because they may well be accessing more power than they are used to - which is different to what standalone engines can do at max revs on the dyno.

A sportsbike can lay down it's power fast, in lieu of weight circa half that of a Harley or Victory, so it doesn't need much torque. But it can reproduce it far faster, which is producing additional strain and heat. So it's not always clear cut and belts probably aren't a good solution for race reps (fashion aside)for these reasons and probably more besides.

But I still think for most streetbikes, tourers, customs and non sports bikes in general, it's more than up to the job. I can only think that cost is the only thing that puts manufacturers off from making them EOM? I don't know what a good chain or belt costs these days?

Take a GSXR 750 as an example. Potent bike, right?

From Sport Rider Magazine:
http://image.sportrider.com/f/10562972+w750+st0/146_0807_04_z+2008_suzuk...

I make more HP and far more than double the torque. My dyno graph:
http://i177.photobucket.com/albums/w225/half_crazy-01/DYNOGRAPHSAELARRY.jpg

That's what I meant.

"Ummmm.... no"
... you're a very clever guy, but your comments sometimes come across as arrogance, rather than a personal view. Here's a chart showing circa 70hp and 90 lb.ft, they're not hard to find: http://tinyurl.com/czat2ph Different dyno's will often produce different results with the same bike. I've ridden loads of Victory's and Harley's, I like both and I know which models suit me. But America doesn't make the best V-twins anyway IMPO.

"I make more HP and far more than double the torque"
... but you seem to have conveniently forgotten, that you've more than 'doubled' the capacity and then tuned the bollocks off it - go figure! A 106 ci / 1731 cc inline four, of the same technical design, with the same state of tuning, would produce more torque. Kev is a much cleverer (and slimmer) man than I and I'm sure he'd be happy to give the technical jargon as to why, if you disagree with that statement I've put forward.

"Belt costs between $150 and $200 US Dollars"
... that seems very reasonable, I would imagine as cheap as a good quality chain? So a belts service life is actually cost effective it seems.

"I think a twin making the same power as a four will trouble the final drive (the whole transmission) more than the four. I think the peak torque spikes will be higher and more pronounced, even though the average torque will be similar"
... I think it might be convoluted? On face value the punches are going to be stronger, because even if we have a twin and a four producing the same torque, because the twin revs lower and it's torque is therefore more accessible to most riders it will be accessed more often, so there's a theoretical double-whammy of stronger punches and them happening more often between the turns in the road. But equally, they do say that twins are kind to tyres because the pulsing allows time for the tyre to recover and re-grip better when it's starting to wear. Well I guess we can't have it both ways can we? The pulsing either gives the driveline (belt and tyre at least) an easier time because of the pulses, or this advantage is outweighed because the pulses tend to be heavier and accessed more often? I'm not sure, maybe Jag or Half Crazy could better comment? I do know that my chain drive Diavel put out a lot of power and decent torque and that didn't need it's chain adjusting in the first 2,500 miles - so maybe twins are kinder to their drivelines?

It's my belief that you cannot measure power at the crank any more than you can measure horsepower. Both are extrapolated 'calculations' of torque and how frequently you can reproduce those torque punches.

Let me put this just as arrogantly as you choose to take it. Neither of those graphs is a bone stock bike. That's an aftermarket company that makes performance goodies. The graph I showed you was three bikes, all bone stock, all on the same dyno, and all on the same day, so are you going to say it was a dyno variance that made the HD the least powerful bike? The HD makes .6 HP/CI and the Victory and Yamaha make closer to .8 HP/CI. It is what it is. This is not my personal view, it is strictly the fact of the matter. If you would like more supporting evidence I would be more than happy to provide it.

Being this discussion is about belt final drives, I used the comparison to make a point... a point related to the belt final drive's ability to survive under a seriously high torque load. Others have been marginalizing this, saying it is somehow getting a softer power application. I was just making the point AGAIN since no one seems to have been listening the last several times I made it (as if the Boss Hoss and Sabertooth belt driven bikes weren't enough to adequately demonstrate my claims).

Seven hundred fifty horsepower!
"Yes, but it's a SOFT 750 horsepower"

Additionally, I never said that a big twin was in any way superior (I really love triples, by the way) to a multi, nor that it makes more power per litre. The statements I made were intended to be taken in the context of a discussion about final drive systems only. This is not a who has the larger manhood competition, after all.

The more cylinders you have, the more smoothly the power is applied to the driveline. If you want, I can ask Kevin to to give the technical jargon as to why, if you disagree with that statement I've put forward. (just funnin' with ya).

Maybe I'm just not fitting in here at the good ol' boy's country club. Maybe it's the language barrier. Who knows?

yes

Both are true/measured rear wheel torque figures.

You make me want to stab myself in the eye with a sharp #2 pencil.

The rear wheel was turning a drum connected to a Dynojet Dynomometer... the motorcycle was in the closest gear to 1:1 ratio (5th). The measurement was how much torque is being applied to the drum.

Victory lists claimed power figures (as do most manufacturers) at the crankshaft. The 106" (1731cc) Freedom engine is rated at 92 HP and 113 TQ. In reality, on a Dynojet chassis dyno like my graph came from it would make 81/97 on average. The reason I say this is to show that this type of dyno is measuring true rear wheel torque and not calculating it at the crankshaft.

http://www.bristoldyno.com/info/whatis.htm

No worries - you are still drag racing something that most people would no more take to the drag strip than they would fly to the moon.

The Diavel is brilliant on all fronts - apart from the fact I haven't fitted a Scottoiler to it yet, having not figured out a mounting location for the dispenser.

I get to the drag strip once a year. The bike is run unchanged from how I ride it every day. Not a race bike in any sense. I just like to know what it will do and it's FUN! Taking home the #1 Qualifier plaque and a trophy is nice too. My grandson displays them in his room.

That's what I hear. I traveled to the International Motorcycle Show just to see that bike and have a sit on it. I definitely want one.