Gear ratios 219 vs 35

The issue here is that we are not piloting a small sprocket, but rather an entire vehicle, and one that is still subject to the same final drive ratio. In other words, any gains realized in the sprocket department are disproportionately outweighed by other factors/masses involved. This is my opinion.

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No Matt, that’s the point of my offer. I don’t want to buy anyone beer. :joy:

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So, no beer for Dom? I wasn’t very optimistic. I run all sorts of gearings in sim and tend to agree. (Am ex drunk so wouldn’t take you up on it anyways).

Isolated, yes. Flywheel effect. However, the acceleration of the sprocket is negligible compared to the 350lb kart it is hooked to. Dang physics is hard IRL.

There is time in chain/gear optimization. I have contacted the most knowledgeable people on the subject like Stuart Burgess.

Lighter chain>Heavy chain
Front driver must be 14t or higher!
The larger the rear gear the higher the loss
Waxed chain > oil lubrication

Now, the reality is 99% of people wont see a difference between the best setup and the worst (same ratio) because your talking very small numbers but there is alot of really smart people doing advanced research on the topic for things like Olympic Cycling and Motor GP and they are NOT the same because RPM and Loads are completely different but my opening statement is always true regardless.

I would agree with your first statement. The closest I think you could “test” the larger driver vs a smaller driver with the same ratio would be with an RC car and the reality is while there may be a slight difference in certain parts of the track the reality is the lap times will be the same. Perhaps the further apart the difference with the same ratio the more likely you would see a difference, but as someone else said, set up and driving is where you need to be spending your time.

If there’s a difference wouldn’t you be able to see it on an inertia dyno? Take out all the kart/track/driver variables.


You can see it on the Dyno…

Also, there is some good scientific papers on it.

There is some differences between motorbike and kart chains that change the optimization formula mainly mass and articulation losses. (Roller vs Bushed chain) also, rotational RPM of the sprockets (mainly the large end) vs MPH as motorbike tire are much larger Diameter then a kart tire.

50 laps 9.66 (7.33)
18.204 w/ 17.993 optimal

50 laps with 12-88 (7.33)
18.231 w/ 18.018 optimal

Did not seem to be different, really

You must have one hell of an accurate and precise dyno for 8hp engines.

I just use our DynoJet Chassis Dyno, in conjunction with a wideband for track correlation.

Seems to be be very repeatable and even small changes seem to show up. Its nice to have atleast some control over environmental conditions as well. Amazingly enough spinning a 2700lbs drum with a 9-10HP Kart seems to work well. The self start feature allows you to spin up to clutch lockup speed and with a stinger it doesnt have any problems. I do change gearing on kart so pull length on Dyno is very similar to T1-T3 at G&J with my most used gear ratio.

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