Landracing Forum
Tech Information => Technical Discussion => Topic started by: Jonny Hotnuts on May 16, 2008, 11:07:16 PM
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Someone told me it was better, as in easier on the drive, if you were to use the largest countershaft sprocket and achieve gearing by your primary drive. This person said that it was needed to keep chains from breaking.
For instance:
17-35=[2.06] makes almost identical gearing to 19-39=[2.05]. While the gearing is basically the same this person told me that it was better to run the bigger sprockets....even thought I cant understand why this would have any affect. The HP/torque of the motor is the same, the drive speed will be the same and the same resistance forces at a wall speed are the same.
So was this person crazy or is there some merit to the statements that I dont get?
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Someone told me it was better, as in easier on the drive, if you were to use the largest countershaft sprocket and achieve gearing by your primary drive. This person said that it was needed to keep chains from breaking.
For instance:
17-35=[2.06] makes almost identical gearing to 19-39=[2.05]. While the gearing is basically the same this person told me that it was better to run the bigger sprockets....even thought I cant understand why this would have any affect. The HP/torque of the motor is the same, the drive speed will be the same and the same resistance forces at a wall speed are the same.
So was this person crazy or is there some merit to the statements that I dont get?
I can't see too much difference with your 17 vs. 19 tooth primary sprocket, but if you geared it the same with say a 12 tooth vs. a 17 tooth then the chain going around the 12 tooth is not as good a deal as it is turning around a smaller radius.
I just know from my motorcycle days you wore the chain out faster with a smaller front sprocket.
I'll be interested in others thoughts on this also,
Sum
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Larger c/s sprockets definitely make the chain life better , it's the whip around the radius that's hard on chains, but as for saving on chain breakages, but if you are that close to your chains breaking point, investing in a stronger chain would make more sense than changing sprocket sizes , after all , LSR is not about getting another 1000 miles out of a chain ? :?
Tiny
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The fact that a larger sprocket combo increases radius making the chain links pivot less could be a factor in how much heat it builds. I will bet this is the basis of what the reasoning was and not the stress load on the chain itself.
As far as chains go I am using the D.I.D. X-ring 530 ZVM2. I have used the EKZZZ 530 and have had good luck with all the quality chains….and as far as mileage…..here is last years chain (and an expensive chain to boot) with only about 25 miles on it!
(http://photos-579.ll.facebook.com/photos-ll-sf2p/v240/69/50/1114496579/n1114496579_30064406_5451.jpg)
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Also how much would I expect the diameter of a 22" tire to grow at speed, a little off topic but I am trying to figure out gearing. I assume that a 22" tire will grow about .5" at speed.
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hey hotnuts excellent chain maintenance :? I use tsubaki 530 HQR non oring chain on my turbo bikes, busa is running a 20T front ,35T rear with TTS 12% overdrive 5trh and 6th , , the master links recieve a dab of silicone (after cleaning with acetone) no problems to date ,and because Im a run on the smell of an oily rag racer :-D here are my secret chain maintance tips ,after a hard week on the salt I try to dismantle /clean the bike as soon as possible to counter the effects of salt corrosion , 1. remove chain and place in a solvent bath , clean thoughly ,remove ,drain & dry , move chain to kitchen sink ,wash with hot soapy water ,dry ,inspect chain for any damage ,if ok place in a container of engine oil and seal ,leave untill required again , to prepair for the bike again ,,remove chain from oil and allow to drain for 24 hours (this removes most of the excess oil ) wipe clean and inspect for any rust / corrosion ,I use a white lithium grease to lube the chain with , it comes in a solvent base and is like water ,place chain in a container of lube and agitate chain ,this allows the lube to access all the links ,rollers etc , remove chain and allow solvents to flash off , chain is now coated with a thin thick coating of lube , it does not fling off easly , chain iis ready to be used again :-D
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hawkwind, you mean the chain I have in the pic isnt suitable for use this year....I figured with a little wd-40...... :-D
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hawkwind, you mean the chain I have in the pic isnt suitable for use this year....I figured with a little wd-40...... :-D
........ it looked good to me, it fact I was going to ask if you would consider selling it to me since it had history and that might help my car.
Hawkwind great info, I'll save that, thanks,
Sum
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Jonny,
Going to a larger sprocket will actually reduce the tension load on the chain. If you think about it, torque is force X lever arm, so if your engine make 100 lb-ft of torque and the sprocket has a diameter of two feet, i.e. radius is 1 foot then the chain would have 100 lbs of tension at your maximum engine torque. If you went to a sprocket that is 1 foot in diameter, radius = 1/2 foot then the chain tension would be 200 lbs. So going with the largest countershaft sprocket does reduce the tension on the chain. Looking at the difference between a 17 tooth sprocket and an 19 the tension reduction would be about 18%.
As posted previously reducing the radius that the chain has to go around is probably the biggest advantage of the larger sprocket.
Rex
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hey hotnuts excellent chain maintenance :? I use tsubaki 530 HQR non oring chain on my turbo bikes, busa is running a 20T front ,35T rear with TTS 12% overdrive 5trh and 6th , , the master links recieve a dab of silicone (after cleaning with acetone) no problems to date ,and because Im a run on the smell of an oily rag racer :-D here are my secret chain maintance tips ,after a hard week on the salt I try to dismantle /clean the bike as soon as possible to counter the effects of salt corrosion , 1. remove chain and place in a solvent bath , clean thoughly ,remove ,drain & dry , move chain to kitchen sink ,wash with hot soapy water ,dry ,inspect chain for any damage ,if ok place in a container of engine oil and seal ,leave untill required again ,
Hawkwind,
Do you run a master link? Or do you break/re-rivet the chain every time?
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Rex wins the six pack :-D
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Does anybody use an onboard chain oiler? At the speed of the chain and the length of the run it certainly makes sense. I raced karts in the 70's and the race was an hour and a chain oiler was the only was to make the chain last. Of course the oil went right on the track. You would have to make a cover for the chain to collect the oil.
Rex! Excellent answer.
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Does anybody use an onboard chain oiler? At the speed of the chain and the length of the run it certainly makes sense. I raced karts in the 70's and the race was an hour and a chain oiler was the only was to make the chain last. Of course the oil went right on the track. You would have to make a cover for the chain to collect the oil.
Rex! Excellent answer.
This reminds me of an old Bultaco... Sr. Bulto had the right idea!
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Does anybody use an onboard chain oiler?
3 of my old HDs have auto chain oiling, I think 1 of them is intentional... :|
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Jonny,
Going to a larger sprocket will actually reduce the tension load on the chain. If you think about it, torque is force X lever arm, so if your engine make 100 lb-ft of torque and the sprocket has a diameter of two feet, i.e. radius is 1 foot then the chain would have 100 lbs of tension at your maximum engine torque. If you went to a sprocket that is 1 foot in diameter, radius = 1/2 foot then the chain tension would be 200 lbs. So going with the largest countershaft sprocket does reduce the tension on the chain. Looking at the difference between a 17 tooth sprocket and an 19 the tension reduction would be about 18%.
As posted previously reducing the radius that the chain has to go around is probably the biggest advantage of the larger sprocket.
Rex
Rex,
I always your posts carefully, so I can learn as much as I can. If you reduce the radius doesn't that make the sprocket smaller? Maybe at speed week I can have one of those beers. Make mine O'Douls.
Nothing was said in this thread about the transmission shifting better when it was turning faster, which a large primary sprocket provides. Maybe that was only in the old days?
Looking forward to seeing you Speed Week if I can make it.
Harvey
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[/quote]
3 of my old HDs have auto chain oiling, I think 1 of them is intentional... :|
[/quote]
funny! but so true.
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Rex is right. At the drag strip, the high horse powered busas that run a 15 tooth front sprocket are harder on their chains and are more prone to rounding the teeth on the front sprocket. As you use more teeth on a sprocket, the individual tooth and chain roller load gets reduced because your engaging more links simultaneously. It would probably also help reduce the heat generated by a really dirty chain. :-D
Scott
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Here is where I am having the problem:
At the drag strip, the high horse powered busas that run a 15 tooth front sprocket are harder on their chains and are more prone to rounding the teeth on the front sprocket
(http://photos-f.ak.facebook.com/photos-ak-sf2p/v257/69/50/1114496579/n1114496579_30067349_4779.jpg)
I am not talking about changing one sprocket that will change ratio, ture many drag bike guys lower the counter to get a harder launch (and becaue most busa are not doing 200mph in the 1/4 and dont need that high of gearing) but they dont also decrese the size of the drive sprocket. True a smaller counter sprocket will lower the ratio and pull harder on the chain. I am talking about increasing both sprocket sizes incrementally, retaining the same gear ratios.
I am certain that a larger sprocket will have a heat reducing affect….based solely on the fact that friction is reduced because the amount the links pivot is lower. This is because the larger radius they have to travel around the sprocket. Let face it, if a chain did not have to go around any bends it would not build heat.
I am NOT convinced that the chain load (X) will change between examples if torque loads and speed loads are identical if the gear ratios are the same.
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:-D Hi Jonny,
In the scenario that you have illustrated, you are nearly correct. Your ratios DO remain the same, however if you consider the radius of the countershaft sprocket as a “lever”, the shorter the lever, in this case, the more torque or "force" you will apply to the chain.
Back in the 70’s when I was doing a lot of Karting (Sprint and Enduro) we found the kart pulled harder out of the turns when we used the smallest countershaft sprocket that would allow the chain to “live” for the duration of the last practice session (to get rid of the chain stretch) and 1 hour race. The top speed was the same with either sprocket as verified from the maximum RPMs. Sprint proved to be the same but wasn’t quite as noticeable because of the abundance of torque due to the lower gearing. Again, maximum RPM proved the same top end speed.
Since the very small benefit in torque you may obtain from the smaller countershaft sprocket won’t make any difference in your top speed, you should use the largest sprocket combinations to keep your chain alive. 8-)
Hope this helps a little.
Yours in Sport
Terry A. Hume
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jonny i think you are right --there is something to consider though the bigger the sprockets the faster the chain speed --what i try to do is run a big enough sprockets so the sprockets dont wear out and small enough to keep the chain speed as slow as possible--i buy cheap chains and expensive sprockets --i race 3 races at el mirage and throw the chain away --speedweek and throw the chain away --3 more races at el mirage and throw the chain away --total cost 3 chains 104 dollars and the sprockets still look new - willie buchta
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(http://photos-d.ak.facebook.com/photos-ak-sf2p/v257/69/50/1114496579/n1114496579_30067523_9660.jpg)
For argument sake lets say you could progressively add identical weight to the 25 LBS blocks.
Because the gear ratio is identical both 50 LBS blocks would raise at the same time AND at the same rate.
I would think that the chain load between the sprockets would be the same if this were true.
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Wrong Jonny. Because of the size of the larger sprockets the weight on the right would raise twice as far in the same length of time as the weight on the smaller sprockets. The circumference of the larger small sprocket is twice that of the smaller one. Remember, the small sprocket is driving and not just an idler.
Pete
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if the ratio is 2 to 1 on both sets of sprockets then if you turn the small sprockets 1 turn then the big sprockets will turn 1/2 turn the only differance is the chain speed ---you might pick up some leverage on the smaller front sprocket but you will loose it when the rear sprocket transfers power to the rear wheel--- i think-- willie buchta
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:-D All very good arguments. But, when you boil it all down, it is still better to use the largest sprockets that will fit and give you the ratio you need. Keep the chain speed as slow as possible. 8-)
If you race on a different type track and you need to come out of the corners hard, then use the smallest sprocket pitch diameters to give the added leverage on the countershaft sprocket. Just remember, your chain will run hotter due to the constant flexation from the smaller pitch and may not last in a long race. :wink:
Terry
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Nice discussion. I looked at this for a couple of days and used all my spare time thinking about it. Not much time which is why it took so long to find the missing piece.
If you add a wheel to the bigger sprocket and attach the rope/chain/line from the weight to go around the wheel, which will be the same size on both examples, then we find the lift speed is the same. A full turn of the small sprocket will turn the large sprocket a half turn, turning the wheel a half turn. The same for both examples.
Clear as mud!
Geo
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Jonny,
Regarding your second drawing of the two sprockets and the 25# and 50# weights, the tension in the chain from one end to the other is 25# the ratio and the sprocket sizes have nothing to do with the tension in the chain. To make the 50# block to move upward you will need to add 25# plus in efficiencies to the 25# side and this will make the tension in the chain 50#. Again, per your drawing the ratio between the two sprockets will have nothing to do with the tension in the chain, it is 25#.
Rex
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Here is where I am having the problem:
At the drag strip, the high horse powered busas that run a 15 tooth front sprocket are harder on their chains and are more prone to rounding the teeth on the front sprocket
(http://photos-f.ak.facebook.com/photos-ak-sf2p/v257/69/50/1114496579/n1114496579_30067349_4779.jpg)
I am not talking about changing one sprocket that will change ratio, ture many drag bike guys lower the counter to get a harder launch (and becaue most busa are not doing 200mph in the 1/4 and dont need that high of gearing) but they dont also decrese the size of the drive sprocket. True a smaller counter sprocket will lower the ratio and pull harder on the chain. I am talking about increasing both sprocket sizes incrementally, retaining the same gear ratios.
I am certain that a larger sprocket will have a heat reducing affect….based solely on the fact that friction is reduced because the amount the links pivot is lower. This is because the larger radius they have to travel around the sprocket. Let face it, if a chain did not have to go around any bends it would not build heat.
I am NOT convinced that the chain load (X) will change between examples if torque loads and speed loads are identical if the gear ratios are the same.
Hi Johnny,
I'm not sure how to do all the math but If I visualize leverage points I can see how the torque on the chain would go down as the diameter of the countershaft sprocket gets larger. If I take one of my bath fan motors and try to stop it spinning by pinching the shaft I have to apply a lot of force. If I install a 10 inch disk on the shaft and pinch the outside diameter its pretty easy to stop even though its spinning way faster. This is because I have a big lever arm advantage the further I pinch the disk from the centerline. This tells me that max torque on a driven shaft is at the centerline and as you move farther away from the center as in a larger sprocket the torque at any giving instant is smaller but the chain speed is higher. The rear wheel should work in the same fashion. Power is applied to the center of the wheel and the torque gets applied to the ground by the outside diameter of the tire. If I sit on my bike in the driveway with the front brake on and hold the tach at 3000 rpms and drop the clutch with a 30 tooth rear sprocket the engine would die. If I did the same test with a 100 tooth rear sprocket the tire would break loose. This is because the distance of the lever arm between the outside diameter of the rear sprocket and the outside diameter of the rear tire has been shortened. So now it takes less of a chain yank to bust the rear tire loose. When I apply the current images in my head to my bike with a 15 tooth front sprocket and a 30 tooth rear, I see the chain applying a lot of force to the rear sprocket to get the rear tire to bust loose. When I change the sprockets to 30 teeth front and 60 teeth rear I see less force being transmitted through the chain and less force being required to bust the rear wheel loose since it has a bigger sprocket. In the end I see a difference of chain pull and chain speed between the 2 combinations but the amount of torque that hits the ground is the same.
Scott M
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:-D Yep! That be correct thinken. :wink:
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From what I've seen, the most efficient sprocket setup is a ballance of chain speed and sprocket radius.
The weight, power, and drag of each machine has its own requirments, so like most things you have got to fool with it a bit before you get it right.
Just my opinion,
Don
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Originally I posted this because I was fighting with the idea of sprocket sizes VS HP VS tire size (and growth).
I decided that a 19 would be the best choice this year because it makes the hypothetical top speed 210 at redline in 6th but the motor stops making power @ 9500 (red is 10900). If the tires grow 1/2 inch 9500 rpm is just around 201.
And with enough spray anything is possible!!!!!
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dont forget that tire slippage willie
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Come on Willie, let the kid dream, we all know in this sport even the most unlikely dreams can come true.
Keep the faith JNuts, you are on the right track.... as soon as you are on the long one that is :-o . Small motor advice... Gear lower and get the 175 first, then you have room for the long gears.
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Originally I posted this because I was fighting with the idea of sprocket sizes VS HP VS tire size (and growth).
I decided that a 19 would be the best choice this year because it makes the hypothetical top speed 210 at redline in 6th but the motor stops making power @ 9500 (red is 10900). If the tires grow 1/2 inch 9500 rpm is just around 201.
And with enough spray anything is possible!!!!!
Jonny,
If your using a stock Busa ECU you can raise your rpm limiter. Email me and I will give you the details.
Scott M
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dont forget that tire slippage willie
The cars motor is over the drive wheels.....this helps.
--ALSO--
I have a traction control system on the car. The rear spoiler on the car is computer controlled with high speed actuators. If there is an appreciable difference in speed between the front and rear wheels the actuator raises the spoiler 1” and pauses and will continue to raise by 1" up to the legal limits (or desired) for spoiler angle. It will also lower the spoiler in one inch increments (30 second pauses), if no additional slippage is noted.
-JH
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Moving the spoiler is at that rate is too slow.
DW
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:-D At speed, probably a 3 to 5 second pause might be closer. 8-) Lean on the short side :wink:
Terry
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Moving the spoiler is at that rate is too slow.
DW
Yep, that is only 2 moves in a run at the speeds you want to go over 5 miles.... yes the run will take a little longer than 1 minute but the spoiler will not be effective until you are over 100... :|
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was changing sprockets on my bike yesturday and something came to me that i forgot to mention --you want the chain and sprockets to wear evenly if you run a front sprocket that will divide into the rear sprocket ( 24 x 48 ) the chain wont wear even ---much better to run one even number sprocket and one odd number ( 24 x 49 ) the chain and sprockets will last a lot longer --just something i learned over the years willie buchta
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Archimedes is spinning in his grave.