chuckharrisjr

iTrader: (30)

Thanks for info I appreciate it. So will a bigger or smaller spur have a cooler running motor?

rocket-mtrsprts

iTrader: (1)

Not really, though getting up to speed quicker helps the motor run easier as there is less strain on it.

chuckharrisjr

iTrader: (30)

Gotcha thanks again....

AreCee

iTrader: (1)

I'm sorry, but I can't follow your logic.

Are you saying that a larger spur gear and larger pinion will give quicker initial acceleration than a smaller spur and smaller pinion with the same FDR but spinning up less mass? I would think that the larger mass would be slower to spool up.

BadSign

iTrader: (15)

When my off-road track switched from 27T to 13.5, we all geared about 6-7 teeth higher (48 pitch) on the pinion. I think that's 8 or 9 teeth on 64P

BadSign

iTrader: (15)

heavier gears place more load on the motor, which raises amp draw and increases torque from a dead start.

AreCee

iTrader: (1)

So if heavier gears give you more torque then why do we buy lightened gears with holes in them and pinions machined from aluminum. We should be using solid steel spur gears and steel pinions in 64P for mod motors. Right!

I guess all those physics classes must have confused me.

BadSign

iTrader: (15)

Place more load on a motor and it creates more power. Just look at any dyno sheet.

Too much load, though and we all know what happens- the power to weight ratio goes downhill, and the power curve doesn't improve enough to make up for the additional rotating mass. It's the law of diminishing returns.

It's really a nit-picky thing. All my pinions are aluminum, but steel is just fine.

rocket-mtrsprts

iTrader: (1)

When you're talking about gear size versus spinning up mass I guess you're forgetting the most important part of the scenario -- and that being the relationship between the size of the spur gear relative to the rear tire.

John Tag

iTrader: (42)

Heavier gear were used in PAST for larger Oval racing to keep RPM range up and motor rotion up. Light wt gears are choice now days for all racing. Lighter always spool up faster. Put a brick on your motor shaft see how long it takes to turn over..

BadSign

iTrader: (15)

That's why I said it's a real nit-picky thing. I guess my words should have been "too small to make a noticable difference"

AreCee

iTrader: (1)

We've had similar arguments regarding bicycle gearing before. Finally someone put a power meter on his bike and we tested the different big ring/cog vs small ring/cog that gave the same ratio. The results were that the power was equal in both combinations.

I will assume that other than an infinately small difference of mass that you would never notice any difference using different sized gears as long as the final drive ratio or rollout is equal.

Bigger Brother

I can't believe some of the small numbers you are talking about running....... :O A few weeks back at one of our regional champs, I had one of the fastest cars down the straight in 13.5, using a Novak SS with the standard (sintered) rotor, timing slightly above 0, geared at around 5-5.1. Speedo was an LRP TC Spec with punch on one from the highest setting. Motor was temping around 130-140 F.

Although it was on a really small track - something like a 30m straight, so maybe thats why I was geared so differently from the numbers you're talking about??

AreCee

iTrader: (1)

Our tracks are similar in size 100' x 40' (30x12m) and using an FDR of 4.5 my motor temps at 155-160F or 68-71C after a 5 minute qual. with the ambient temp around 80F or 27C.

Grizzbob

iTrader: (2)

Yes, the track that the original poster & I were talking about is fairly big, has a long back straight & a VERY high-speed sweeper right after(at least it's that way every time I've raced there). But while I would gear my cars at about 4.6FDR there, here at home, I gear it at more like 5.1FDR, because of the smaller track we have here(near Tulsa, OK) to get in the ballpark.....