gearing help
 

i need help with gearing. i've already got mod 1 13 and 15t pinions.

my setup:
g2r
lmt 1950/8 non hi-amp
bk 12020
6s 20c lipos
emax tranny
strobe slipper/ofna 51t spur
40 series wabash wheels/40 series crimes (5.8" dia.)

i used a gearing calculator and figured on roughly 36mph top speed with 15t pinion. seems a little slow. did i figure correctly? thanks,carl

Maybe a 16?

looking for a little more info. what final drive ratio should i shoot for while racing and for bashing?

you should be hitting atleast 40mph, no?

it seems to me that i'm going about 40-45mph, but i plugged all the info in and came up with 36

Do you have a link to a gearing calculator? I think final drive ratio should be somewhere around 18:1....I think...

i found the link:http://www.scriptasylum.com/rc_speed.html

Well it seems as though a 18 tooth pinion would be about right. Especially since I run a 10XL (only 30rpms per volt different) with 20/51 on 14 cells.

so that puts me at about 13.9 fdr and 43mph? is that what you came up with. what factors made you say 18t. i'm trying to understand all this gearing stuff. thanks, carl.

Well tally. Did you figure in the tire swell into the figures as well. If the tire grows .2 in it really increases the speed. If you are happy with the truck and run time that is the man thing with good temps. I run a 15 51 gearing with 3.31 diffs and 2 speed emaxx trans. I am happy with it. I run bigger tires to. The motor you have is rated under load. I wonder if they under rate them some time.

one time i figured it in just messing around. my tires don't balloon much 'cause i taped them. how tough is my tranny, gmaxx single speed, flm half case, steel idler, all boca bearings? i think i'm losing power somewhere. slipper seems ok, using mgt spring on a strobe, almost all the way compressed. how do i tell if its my diffs stripping? need help.

Well I run my spring all the way compressed. I find it will slip if got it little loose. The single speed is tough. I ran a 2250 on one. It would shear the pegs off on the pressure plate. If the diffs start to stripe it won't last long.

with the body off i can sometimes hear a high pitched noise, slipper slipping? i know it isn't the motor. what do you think?

Well with the setup you have. You are applying more force on the slipper than i am. I can slip my slipper pretty easy if choose. I don't like to but can. It very well can be your problem. I am unsure of a great solution.

Try to tighten the slipper as tight as you can. Thats what I do and mine still slips...

i tightened it all the way, no difference. i think eveything is ok. on grass it doesn't get the same traction, just seemed like the slipper was loose. i guess the tires were breaking loose with less traction. thanks, carl.

You can take if off make sure the grease from bearing did not come out and get all over the plates. That will cause it to slip. Make sure you didn't shear the pin off in the plate to. While you got it apart you can see if it was slipping or not to.

will try coolhand.

everything looks ok to squee and myself. check my "burnt slipper pads" thread in brushless, it has a pic. thanks, tally.

After running it for a while, feel the slipper plate. If it is slipping a bit, it will be quite hot (be careful not to burn yourself like I did once!).

As to the rc speed calculator: the speed calculations were made based on the various gearing (which IS correct BTW), motor kv, battery voltage, and tire diameter. Factors such as weight, rolling resistance, drag, real battery voltage, and actual kv can have a significant impact on the real-world result, especially at higher speeds.

For instance, in the RCM store, the Wanderer motors there are listed with loaded kv values. However, if your model is quite light and you are running at top speed, maybe the actual kv approaches the unloaded value instead? Or the actual kv value of your motor may be slightly higher than specified. The battery voltages listed are based on 1.2v for NiMH/NiCD, and 3.7v for Lithiums. NiMHs can be higher, like 1.3v under a light load, and Lithiums can be higher as well. This can also make a difference.

There are so many factors to take into consideration that it is difficult to come up with something very accurate. Even in my experience, my Revo seems to go faster than I calculated. But, I can't simply add a "fudge factor" to compensate because of the vastly different vehicles and it would be inaccurate at best. Unfortunately, I realized all this after I finished it.

its still a good baseline. at least you'll be in the ballpark by using the calculator. a useful tool!

Thanks! Glad you like it.

To get a baseline range, enter values like you have been. Then, enter optimistic values like unloaded motor kv and a battery voltage that uses 1.3v per cell (or 4v for Lithium) to get the maximum possible speed. Your real speed should be somewhere in between.

thanks, i'll try it.

I found it pretty accurate for my 10XL in my Revo but not so with my XL3100. With my XL3100 it was doing over 50mph easy on 12 cells but the calculator said 32....20mph off is a big difference. Whereas, it said 42 for my 10XL which is about right. Why was it off so much on the Lehner motor but not the Feigao?