Here is the deal: went from 15 tooth clutch bell to 17 tooth, so it is 13% more teeth, or 13% faster. Also, went from 60 tooth spur to 56 tooth, so 7 % difference there, or 7 %faster. So is it safe to assume the total difference of gearing now is 13%+7% = 20% faster????
The truck is an Nitro Evader, not that that will matter, the original speed I guessed at 38 MPH, so with 20% more top end speed will it now run 45.6 MPH?
Thanks, Joe

Haven't ran it yet, plan on having some "me" time tomorrow and run it to see if I notice a difference, or to see if it will even move off the line without a push from me with the new gearing.

I dident go over your calculations to closley but it seems right. altho you have to factor in drag and friction. the faster you go the more wind resistance and bearing or bushing drag you will get.

speaking of gearing and what not, how do you factor gear ratios? and what are the stock gears and gear ratio on a team built rc10gt (few years old)? i have a o.s. .12 cvx that needs a rebuild so i'm using that as an excuse to get a new engine. i'd like to get a fantom fr12 or somthing of that nature. at the very least i'm getting a .12 cv-r. and seeing as how my current engine would reach top speed in 3-5 seconds i want to re-gear it. any suggestions?


oh yeah. and whats one of the most powerful .12 engines that will bolt up to my rc10?

Is that the BX gearing? If it is.. then your calculations wouldn't be correct based on your first speed. Thx BX (fastest of the evaders) has been officially clocked by two review's at 34.X MPH. So an ST would never hit that with stock gearing and stock sized tires. The only way your going to hit 45 is with the 21t or 22t gear ran off that custom clutch bell you can get for the evader (with the 56t bx spur gear).

yoster,
Traxxas has a claim of of 37.8 for the Evader ST, which is in line with all the reading I Have done , taking personal guesses with a grain of salt.
So I will still stick to the fact it will run 38 MPH stock, being traxxxas will not exaggerate a competitor truck to be faster than it really is to prove their point of the Jato being the fastest of all.
I have done exactly as you suggested with putting the bell and spur in from the buggy, but gearing is 20% different than stock, so what is the drag % increase with the extra 7 MPH? , Maybe 10%?, thus changing my original calculations from 45.6 to 44.8 MPH.
This make sense ........anyone??
Joe

How are you getting that the BX is faster? The BX and ST are roughly the same speed. The BX is geared higher but that's just because the smaller tires effectively lower the gearing. Taller tires are gonna make you go fast than smaller one's, setting aside weight and power issues.

get big tires and good rato ull be fast[X(]

o ya i member a post that his evader topped 50 ya maby he retro fitted every thing so it could hit it tho dont rember

I was just going off gearing alone.. didnt think about tires... but the bx tires arn't even that much smaller than the st ones.. 5mm oustide diameter to be exact. The BX's 2 extra teeth on it's clutch bell, and 4 less teeth on the spur gear should more than make up for the 5mm smaller tire.

I'll paypal someone 5 bucks if they can show proof that their Stock evader BX or Evader ST with BX gearing can go over 45mph (stock tires).. heck maybe even 40mph.. tho you'd only get money if it goes over 45

Here's pretty good evidence that it won't.
http://www.rcuniverse.com/forum/m_27...tm.htm#2721707

Your %age calcs are correct, you can expect 13% more speed with the new clutch bell. Your starting point of 38mph is wrong. A stock geared evader, in perfect tune, on a perfect day, on a perfect surface, will only reach 34mph. On a good day you're likely to see 30. Which means your new bell will give you 38.5 on a perfect day, and 34-35 on a good day. If you get the bx 56 tooth spur, you can expect 37mph on a good day, and 41 on a perfect one.

You can download [link=http://www.rctek.com/pdf/rcgears111.zip]rcgears[/link] and do the calcs for yourself. The evaders transmission ratio is 2.89 and it's engine will rev at 30k (estimated) on a good day, and 33k on a perfect day, perfectly tuned. The stock tires are 4 inch diameter i believe.

well what is the stock spur and bell on a rc10gt? and is it printed anywhere on the gears?

and another question. what does the pitch number mean?

The angle of the teeth. For example.. if u had something crazy like a 90p.. it would be like blocks around the gear.. 90 degree turns at the top. A 32p means that the tooth makes a 32 degree angle to the center of the spur. Doesn't mean anything to you as long as the gears are all the same pitch.. has nothing to do with speed or anything like that.

Higher the pitch, smaller the teeth.

Stock clutchbell/spur on the GT is the same, 15/60. It has a taller transmission ratio though, so with the same rpms from a motor, it will go faster. Evader's transmission is 2.89:1 and the Gt's is 2.6:1

my GT is about 4 years old though so i think the older stealth trannys had a 2.25 ratio. could be wrong though.

Hey Gerwin,

Can you suggest a clutch bell gear ratio combo and where I can get it for my evader st,
I have a OS 18 cv to put in it. what do you all think.

Thanks

the CV should be strong enough to pull both the stock gears and the BX gears (17t clutchbell, 56t spur)

You will get better acceleration with the stock gears, and higher top speed with the BX gears. If only swapping one gear, the clutch bell will have a much greater effect.

seen as youve done all hese maths youve forgot to notice that it will give more strain on the engine having it higher geared so that will prob knock a bit off aswell, bearings and other transmission parts could be looser or tighter than the stock car you based your whole estimate on, no way of getting it exactly right but if you think of every possible little thing then you could get close but still not perfect
so get a radar gun or venom speed meter to see how fast you really do go, only real option tbh

I know that psot is like 4 months old, lol, BUT....

the GT always had a 2.60:1 ratio, 2.4:1 for the B2, 2.25:1 for the old RC10 and 10T, and 2.60 for the T2, 3, and 4 and the B3 and 4.

That post was based on radar data, both from stock and higher geared rigs. The rpm's were inferred from radar top speeds, not the other way around. There was some speculation, but it was labeled as such.

Working link to post [link=http://www.rcuniverse.com/forum/m_2721707/mpage_1/tm.htm]here[/link].

Thanks for info Gerwin, I replaced the clutch bell with BX's 17t and it tamed the engine a bit, The thing was a wheelie machine with stock gearing and a Blast to drive. It's more fun and controlable as it takes off now