aliens8mycow

Heck, we can speculate each other to death until then, so no hurry!

Do you think the eagletree can tell us the difference (if any) in torque, top speed, etc.? If there is a small difference, it just might be one more thing to help someone who is racing in a very competitive situation, or someone going for a speed record, or whatever. If nothing else, as speed said, it'll take our minds off some of the more common questions for a bit!

tarantis

Wow. That's almost completely wrong and an awful comparison as well.

SkrapIron

Boy, isn't smeone grumpy this time of the morinig?

First gear is small crank gear, large axle gear. 5th gear is small crank and small axle gear. 10th gear is large crank and small axle gear. I was talking about ratios, not the actual gears!. The point is, given the 10 gear setup, it requires you to do almost 10 times the amount of work to get rolling using the taller gears in 10th, compared to the smaller gear ratio is first. Use 3rd gear and 6th gear as an example. If you divide the number of crank teeth by the number of axle teeth, you will find that they both have a close a gear ratio (3rd gear 64t crank/20t axle: 6th gear 84t crank/24t axle). But, the 6th gear setup is taller and requires more work to propel you forward. The third gear setup is easier to get going. The same can be said for the work that an electrical motor has to do to get a mass in motion, given the example gear ratio's.

So, no. I don't think it's a bad comparison at all.

tarantis

The fact that your comparing a gear turned by a crank to one rotating on a spindle makes it a bad comparison. Also comparing 30k rpm to 80-100 rpm makes it a bad comparison. You also don't have the inefficiencies of a chain

Take this gear set up as an example. I chose a 7 speed rear-end because it gives you a wider range of usable gears. Your typical "10 speed" never had 10 usable gear combos. 42/52T on the front and a sprocket containing 15, 17, 19, 20, 21, 23 and 26. Gear ratios only come close to overlapping when the chain is the most out of alignment. You don't do big/big or small/small on a bike because of chain alignment and you can't compare the middle gears because their ratios aren't close.

sleepy23

My Feedback: (1)

i dont know how small it will detect, but we sure will test it to see. i cant imagine a gram amounting to much rpm loss, but i could be way wrong.

aliens8mycow

We seem to have theories on both sides - one theory that the heavier gear will generate more top rpm, but take longer to get there. Another theory that the larger gear will cause lower rpm since it's harder for the motor to turn. Should be fun to see which is right, or if it doesn't really matter.

Speedmunkey

I doubt the difference is going to be 2% either way. But then, I know guys that spend hundreds of dollars trying to gain a 1% improvement.. So test on Sleepy!

savage_beast99

a body in motion will stay in motion, there for the heavier the body the longer it will stay in motion due to inertia. so, heavier gears will get up to the save rpm at a slower rate, but be able to maintain the said rpm will less energy exerted, there for a longer run at top speed is possible. the differences are probably only noticeable on some kind of dyno for the whole car.
also this set of heavier gears would work better on a car with less resistance like a 2wd over a 4wd. you would probably see a difference in energy consumption if you maintained top rpm for extended periods of time but again the difference is probably not noticeable.
thanks for the mentally stimulating post, this is where science meets hobby and it gets fun!!

SkrapIron

I thought about that on my way to a customer site this morning. [] Bad example. A bicycle uses a high torque, low rpm crank and it's gearing to multiply the driving RPM's to the drive tire. The electric motor is using the High RPM divided by the gearing of the drive train to create sufficient torque. It is using 2 different principles of gearing to achieve 2 different results. One is a multiplication of work, the other is a division or distribution of work. Hey, it was early this morning. The coffee hadn't kicked in yet!

So, the concensus is thet the bigger gears will accelerate slower, but run at the top speed longer? I can buy that.

S.A.E.W.O.T.

HEHEHE!...yupperz!...hey is there a thing that i can do 2 make the tranny on my evader better!?

tarantis

Hey I thought about it some more on my way to a customers site as well. Nothing else to think about when driving through 30 miles of boonies.

aliens8mycow

I would think that (while not on the same scale), that larger mass would give you the 'speeding locomotive' deal. It might take a bit longer to get up to speed, but once you're there, it's easier to maintain, or possibly even get a slight bit of extra speed.

If that's true, then going with smaller mass could increase acceleration, so depending on the application, if it's a measureable difference, this might be something that folks could take advantage of.

S.A.E.W.O.T.

or get a big PHAT!... motor like a 6x6!... on 24 cells!....thats if u wanna go fast tho!... if u wanna go slow get a 15x2 on 6 cells!...lol well do u guys think that RRP makes good gears? im jus kiddin 15x2's arn't slow!

aliens8mycow

Within a reasonable price range, rrp gears are good stuff. Sometimes you'll need to 'clean up' the edges, but unless you're super picky, they work well.

acexxxoasis

My Feedback: (4)

for top speed im going with a 100t pinnion and 20t spur gear :P

S.A.E.W.O.T.

YEEEEEEEEEEEEEEEEEEEEEEEEEA!... that would be sick!... thats like all i use is RRP!

SkrapIron

Yeah, I use the RRP stuff too. It's really durable, and stands up to alot of stop and go driving. I've been doing this a long time, I never claimed to be a good driver! I'm going to get my RC10 vid up on the web sometime this week. Still no word from the software vendor. GRRRR.

Other than a rumour, does anyone have any scoop on the E-revo?

pilut12

-coming in late-

i got my physics book in my car right now and i dont feel like getting it, but rotational inertia is very dependent on weight distribution
we need diameters to get actual numbers. if i have the time and still got the internet connection, ill give the formula but its like 1/2*r^2*mass [just looked it up online, this is simplified ie not using integral calc...). but anyways, that number would still mean little until its compared with the torque the motor produces. it seems (very much so to me) that the difference in rotational inertia would have no noticeable effect, but theres that chance the motor doesnt produce much torque relative to the rot inertia that there is something noticeable. i still highly doubt that but the calculations wouldnt be hard to show that there is SOMETHING going on.

as for the maintaining top speeds better with larger gears, i think there would be even less difference than acceleration because drag and friction would slow the car down way more at top speeds making any difference in rot inertia there even more meaningless. and i dont have the knowledge to say larger gears would pull less power from the motor/battery, but id bet that isnt much of a difference either.

sleepy23

My Feedback: (1)

"it seems (very much so to me) that the difference in rotational inertia would have no noticeable effect, but theres that chance the motor doesnt produce much torque relative to the rot inertia that there is something noticeable."

before i cut loose on this quote, please tell me it is in reference to the differences in pinions and spurs and not just in general

acexxxoasis

My Feedback: (4)

100t pinion and a 20t spur would be best I say come on think about it for every 1 rotation your motor makes your spur makes 5.... with a brushless motor pushing 45,000 RPMs easily it would be around 225,000 rpm at the tranny come on that would kick arse

Zorak

my brain is twisted by this braintwister

S.A.E.W.O.T.

ROFL!....that was wicked!....lol me 2!

aliens8mycow

... regarding the quote - I don't think we're looking for a massive difference here. As sleepy said previously, he's not even sure if the eagletree system will be able to calculate a difference. The whole deal is this - take a car with deans plugs on the battery vs. the same car with the battery soldered... in the backyard, you can't tell a difference, but on the racetrack, you can. It's very negligible, but it's there. We're just trying to see if there is a similar difference with gear sizes.

I have to wonder if designers/engineers have never thought this through before. Are the current 'standard' sizes of pinions and spurs that we see based on what fits a standard motor plate, just the same as they always have been, or were these proven years ago to be the optimal sizes?

A lot of racers seek to reduce rotational mass by 'narrowing' their tranny gears. Is the effect huge? No... but it's there. Would using smaller gearsets make a similar difference? We don't know yet. Would the different number of teeth (although the ratio is the same) cause a difference in motor performance? Lotsa questions... and I'm starting to sound like a philosopher... just call me Rene Descartes.

Zorak

OWWWWWWWW MY BRAAAAAAIN
STOP TWISTING ITTTTT

S.A.E.W.O.T.

lol...ok back on topic