Britbike forum

Classic British SparesKlempf British PartsBaxter CycleThe Bonneville ShopLowbrow CustomsGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supplyJob Cycle

Upgrade your membership to Premium Membership or Gold Membership or Benefactor or Vendor Membership


New Sponsor post
Sale and Freebies May 2nd to 9th
by BritCycleSupply - 05/05/23 4:15 pm
New FAQ post
Three issues to look into
by Magnetoman - 05/24/23 1:45 pm
News & Announcements
Premium members! 🌟
by Morgan aka admin - 05/25/23 10:30 am
Gold members! ⭐️ ⭐️ ⭐️
by Morgan aka admin - 05/16/23 2:10 pm
How to guides - Technical articles
Removing Triumph sludge tube
by reverb - 05/08/23 7:30 pm
Sixth edition is now out:
The Gold Star Buyer's Companion
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Member Spotlight
Bry
Bry
Scotland
Posts: 447
Joined: May 2006
Top Posters(30 Days)
Lannis 91
DavidP 79
Allan G 70
Top Likes Received (30 Days)
Lannis 44
Cyborg 23
raf940 22
Newest Members
Michael Pelkey, Myrt, Tim Chandler, Magn0208, tsmeds100
12,520 Registered Users
Forum Statistics
Forums35
Topics77,072
Posts792,655
Members12,520
Most Online230
Mar 11th, 2023
Photo posting tutorial

Previous Thread
Next Thread
Print Thread
#900544 01/17/23 1:19 pm
Joined: Jan 2006
Posts: 2,503
Likes: 127
Britbike forum member
OP Offline
Britbike forum member
Joined: Jan 2006
Posts: 2,503
Likes: 127
We (650 racers) have been aware of some pretty substantial whip on the top chain runs at a certain speed or frequency. Jake has noticed that the event actually saps about 5 hp on dyno runs. As soon as the event is over, the power returns. He's gone as far as converting his bike to a 520 chain to see if the heavier chain is the cause. Same result, though. I've seen it happen with my single carb 500 as well. Seems controlling this would be a good thing.
Is this common to all 360 degree motors? Different chain adjustments don't seem to have an effect.
BTW, Jake's bike has a QPD primary, mine has a Newby and the 500 is a stock chain primary. To me that kind of rules out a lack of cush drive in the belt drives.
Appreciate thoughts.

1 member likes this: Gordon Gray
British motorcycles on eBay
Mike Baker #900545 01/17/23 2:21 pm
Joined: Mar 2019
Posts: 1,617
Likes: 472
Member
Offline
Member
Joined: Mar 2019
Posts: 1,617
Likes: 472


What we've got he'ah... is failure... to communicate.
1 member likes this: Gordon Gray
Mike Baker #900546 01/17/23 3:05 pm
Joined: May 2019
Posts: 1,479
Likes: 616
Britbike forum member
Offline
Britbike forum member
Joined: May 2019
Posts: 1,479
Likes: 616
I wonder if it would be worth trying a chain guide. Mounted just under the chain when under tension. Maybe keep the whip form getting to the point where it’s eating that 5 hp. There would be some friction between the chain and guide, but maybe less overall? Who knows… just a thought and relatively easy to try.
Although…. If it worked, I would think that we would have seen it before. Also might beat itself to death.

Last edited by Cyborg; 01/17/23 3:11 pm.
2 members like this: kevin, Gordon Gray
Joined: Aug 2001
Posts: 6,659
Likes: 830
Life Member
Offline
Life Member
Joined: Aug 2001
Posts: 6,659
Likes: 830
Originally Posted by Hugh Jörgen

Wow……that one went WAY over my head.


Gordon Gray in NC, USA........"Did you shoot our car?"


Mike Baker #900548 01/17/23 3:27 pm
Joined: Mar 2019
Posts: 1,617
Likes: 472
Member
Offline
Member
Joined: Mar 2019
Posts: 1,617
Likes: 472
lol. Mine too!


What we've got he'ah... is failure... to communicate.
1 member likes this: Gordon Gray
Mike Baker #900549 01/17/23 4:06 pm
Joined: Jan 2004
Posts: 5,733
Likes: 258
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2004
Posts: 5,733
Likes: 258
If a Norton does not have the same problem then probably the Norton's rear wheel damper is curing the problem. The rear wheel damper is softer than the chainwheel damper. The tension in the span is not constant.
There is an error in the description of I2 at the bottom of the page, I2 should be rotating inertia of the output sprocket.
Their page on "Calculating Roller Chain Length" should be Calculating Sprocket Distance. To calculate chain length you need the centre distance and length of the tangential lines between pitch diameters. Calculate the number of whole pitches around each sprocket and tangent line, add them, truncate to a whole number then round to the next even number.

1 member likes this: Gordon Gray
Mike Baker #900551 01/17/23 4:31 pm
Joined: Jan 2006
Posts: 2,503
Likes: 127
Britbike forum member
OP Offline
Britbike forum member
Joined: Jan 2006
Posts: 2,503
Likes: 127
I envy people who can make sense of complicated formulae like this. It does make sense that the parts don't play well together.
I've thought that a Norton rear wheel assembly would be a good idea for these bikes. Or some jap rear wheel.
I think a tensioner on the bottom run is in the works- a spring loaded skateboard wheel or something . But that's still a band aid in my opinion.
There used to be a poster here - Beltdriveman- who had nothing good to say about chains operating at the speeds we see.
There's a guy that races an XS 750 that has noticed his bike does the same thing. That's what made me wonder if it's a common 360 degree crank thing. So will a 76 degree crank smooth things out?

1 member likes this: Gordon Gray
Mike Baker #900554 01/17/23 4:52 pm
Joined: Dec 2004
Posts: 11,867
Likes: 345
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 11,867
Likes: 345
I remember reading that having both sprockets an uneven number of teeth is best, one even is ok but never use an even number of teeth on both sprockets. It was connected to harmonics, an easier rule to follow than that formula. Smoothest snatch free chain I have has a tensioner on the bottom run and is an X ring and both sprockets have an odd number of teeth 19 and 49.

2 members like this: Cyborg, Gordon Gray
Mike Baker #900555 01/17/23 4:55 pm
Joined: May 2019
Posts: 1,479
Likes: 616
Britbike forum member
Offline
Britbike forum member
Joined: May 2019
Posts: 1,479
Likes: 616
I doubt that a tensioner or guide on the bottom run would help at all. A guide under the top run maybe? I’m guessing the best you can get is a bandaid. As for the crank, your guess is as good as mine. One would think that changing the power pulses would make a difference. Maybe move the problem to somewhere that isn’t eating horsepower where you need it. I really think the bottom line is that if there was a fix, some motorcycle manufacturer would have used it…. not saying you shouldn’t search for a cure though.

Maybe I’m wrong, but the reason I don’t think the tensioner on the bottom will work is that the missing 5hp is presumably missing at WOT under load so the tensioner is just taking care of the slack on the bottom run. Who knows… I should get back to work.

Last edited by Cyborg; 01/17/23 5:01 pm.
1 member likes this: Gordon Gray
Mike Baker #900628 01/18/23 11:49 am
Joined: Jan 2006
Posts: 2,503
Likes: 127
Britbike forum member
OP Offline
Britbike forum member
Joined: Jan 2006
Posts: 2,503
Likes: 127
I've heard that about uneven numbers of teeth before. But thought it was because an odd # didn't set up a wear pattern on the sprocket like even does.
Worth a try.

Mike Baker #900631 01/18/23 12:12 pm
Joined: Aug 2001
Posts: 9,369
Likes: 268
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 9,369
Likes: 268
Slightly unrelated, but in theory it’s bad (for wear) to have a number of links that is divisible by the number of teeth on the sprocket.

E.g. an 18 tooth gearbox sprocket and a 108 link chain.

We don’t want the same link to always meet the same tooth.

I’m not claiming it matters much. All chains wear out far too fast!


Amateur Loctite enthusiast.
Mike Baker #900632 01/18/23 12:13 pm
Joined: Oct 2009
Posts: 721
Likes: 59
Britbike forum member
Offline
Britbike forum member
Joined: Oct 2009
Posts: 721
Likes: 59
This may sound silly but is your head steady quite secure?

Mike Baker #900642 01/18/23 4:03 pm
Joined: Jan 2004
Posts: 5,733
Likes: 258
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2004
Posts: 5,733
Likes: 258
In gears it is called a hunting tooth ratio. If the wheel sprocket is a multiple of the chain links then the same rollers will engage the same teeth. Since chains develop different amount of stretch in different sections it will be tight then loose. With a hunting tooth the wear is spread across all the teeth evenly.
As TT mentioned, for a chain, the number of links in the chain has to be a non-multiple of the sprocket. Since no rational person would put in an odd link chain (except in MotoGP where they use a special half link and chains are replaced frequently - cannot afford to loose a multi-million $ race because of a $600 chain) the gearbox sprocket should be an odd number of teeth. The rear could be even because the large number of teeth spreads out the load.

Mike Baker #904101 03/01/23 3:08 pm
Joined: Feb 2007
Posts: 2,868
Likes: 141
Britbike forum member
Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,868
Likes: 141
Also check to see that the rear sprocket is lined up with the counter shaft sprocket. If they are miss-aligned? There is a probably a Bimford laser tool for this..


Have a basic plan and then let life fill in the blanks.
Mike Baker #904123 03/01/23 11:30 pm
Joined: Dec 2013
Posts: 6,793
Likes: 397
DOPE
Offline
DOPE
Joined: Dec 2013
Posts: 6,793
Likes: 397


watermelons, and turnips, and a contaminator

and other stuff
Mike Baker #904142 03/02/23 12:30 pm
Joined: Jan 2006
Posts: 2,503
Likes: 127
Britbike forum member
OP Offline
Britbike forum member
Joined: Jan 2006
Posts: 2,503
Likes: 127
Oh yea, this.....Kinda forgot about chains and such what with the 2 rebuilds in the last month or so:[
Made a slider block to go under the top chain run and it has helped if not totally cured the whipping. Jake made one that sits taller than mine and captures the chain vertically and horizontally. Cured his problem.

1 member likes this: Big Al in York
Mike Baker #904214 03/03/23 4:04 pm
Joined: Nov 2011
Posts: 688
Likes: 130
Britbike forum member
Offline
Britbike forum member
Joined: Nov 2011
Posts: 688
Likes: 130
Originally Posted by Mike Baker
Jake has noticed that the event actually saps about 5 hp on dyno runs. As soon as the event is over, the power returns.

I'm curious to know how Jake has tested that. Maybe on a brake dyno, he slowly accelerates, holding the rpm constant at various rpm and watching the chain whip and the dyno at the same time and noting a loss of hp with that chain "event" occurs? Which implies that chain whip may be dependent on harmonics probably related to sprocket ratios and rpm. Of course, we don't usually have a lot of sprocket selections for a given speed and rpm, so for example I run a 21 tooth front with a 35 tooth rear on my B50 land speed bike and the chain is extremely long. I run an idler sprocket near mid point on the bottom run and use a rear wheel with a cush drive, so maybe that helps, but I sure could use that 5 extra hp if I knew at what rpm/sprocket ratios Jake has found to be best or worst! There might be a way to change ratios to avoid those detrimental harmonics. Weight of each component (each which has its own natural frequency) might be important as well, so a harmonic dampener might help, but where to put it?

This is photo of my bike before I added a swingarm and made it 4" longer:

[Linked Image from i.postimg.cc]

Tom

Last edited by koncretekid; 03/03/23 4:17 pm.

Life's uncertain - go fast now!
Anything worth doing is worth doing well. Steve said that. Anything worth doing well is worth teaching to others. I said that.
1 member likes this: pushrod tom
Mike Baker #904274 03/04/23 12:31 pm
Joined: Oct 2009
Posts: 721
Likes: 59
Britbike forum member
Offline
Britbike forum member
Joined: Oct 2009
Posts: 721
Likes: 59
OT, That is a great picture! We have noticed that condition on the dyno where your face is almost level with it. Quite disturbing. Worst I had was a Yamaha 650 'bobber'. The builder decided to omit the head steady and whip was severe. Eventually broke the frame. On my own bike sometimes the little head steady tube will crack and go unnoticed but you can tell from the vibes. Rear cross tube has cracked a couple of times. Not sure which comes first though. Yes, a conundrum! PRT

Mike Baker #904996 03/12/23 9:07 am
Joined: Oct 2008
Posts: 8,476
Likes: 443
Britbike forum member
Online Content
Britbike forum member
Joined: Oct 2008
Posts: 8,476
Likes: 443
So, does this happen with rigid rear suspension, with constant chain tension?


Keep your head up and your stick on the ice.

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"


Moderated by  Allan G 

Link Copied to Clipboard
British Cycle SupplyMorries PlaceKlempf British PartsBSA Unit SinglesPodtronicVintage MagazineBritBike SponsorBritish Tools & FastenersBritBike Sponsor






© 1996-2023 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5