8XL Gearing
 

Hi,

I am new to the forums.

I have purchased a E-maxx 3906 second hand.
The current set up is as follows

UE 8 Sypder Diff: 3.31
Standard Trans locked to 2nd gear 1.72
OFNA 51t spur
Strobe Slipper
2x 7.4v trakpower
BK 9920
Proline 40series Bow Tire 5.8"
Gorilla G3 chassis
8XL motor 2084Kv

I want to gear it to about 40mph

according to the R/C calcuations at
http://scriptasylum.com/rc_speed/_solver.html

It suggests I need to run a 21 or 22 pinion.

Would this cause any heat problems or any problems at all? thanks

Also I'm planing to run 5s in future.

Sounds reasonable to me. 40mph on 4s should be pretty easy to do. Feigaos in general will tend to get warm no matter what you do since their efficiency is lower than other better motors. Stepping up to a Medusa 60 (or 70mm) motor around the same kv would be better.

4s on the 8XL is good, but 5s is pushing it a little. Those motors like to go no higher than ~35krpm before they starting getting too warm. Another reason to get a Medusa because they don't mind higher rpms.

BTW: Welcome to the forums!

The feigao motors heat up no matter what you do. I run at 7xl at 20t pinion and am up to 38-42 mph depending on the timing I choose on the motor. I would get the novak heatsink for the motor. It helps a lot. I would go 22T for that motor with your setup. If you need the extr mph you can play around with timing even though some people recommend against it, it works for me.

Wow! thanks for the super fast reply.

I've got the 21t and rcm XL motor clamp on order.

22t is out of stock :-(

check the speed calc and see what the MPH is for each gear, if it isn't a big difference and you can live with the speed of the 21t I'd go with that. Either way when you melt down the feigao, get a better motor.

If you want more speed just play around with the spur gear. They make them all the way down to 52 or something. At 21t you will notice incredible torque and you will probably not heat up as much as my 7xl. If you havent run this combo you will be thoroughly impressed. I got another stock emaxx just to compare and there is no comparison. With the titans you can have good low end, but dismal high end or good high end with bad low end. With the XL motors you get both.

My 7XL is still going strong. I have learned you cant run it in temps over 100 degrees or stuff starts to melt. During winter you should have no problems. My temps have dropped dramatically ever since temps got down to 75 during my runs.

Thanks guys,

its currently got a 9L with 51/15 in it and temps 215.6 F

I just purchased the 8XL just waiting on the pinon now.

215.6 is way too much for that motor. You should be really careful at those temps you can demag the motors and then it might take the speed control with it. 8xl will work much better. I havent tried running an L motor but for 40mph think it would be overworked.

yeah I figured it was too hot. What is a safe temp to keep the feigao motors at?

IMO, max=160*F, preferably ~140*F. Tough to do over a long runtime.

Mine was getting up to 180 on just street running which I didnt like. I cant imagine how hot it would have gotton in sand or in the grass. When I added 2 40mm fans it didnt go over 140 even during hot ambient temps. I think now that winter is here we are ok. I have only recorded temps of 115 right now with only the novak heatsink.

Thanks guys you have been great help. I think I will be pretty satisfied with the 8XL 51/21 setup.

I think I will stop playing with the Maxx till I have the 8XL in and correct pinon. Just encase I damange the ESC.

I'll run 8XL till castle releases the Mamber Monster Neu combo - should have money saved up by then.

PS guys I'm in Australia.

Thats what I'm doing. I'm going to run the 7XL till the MMM combo too. Good luck.

what price will we be looking at?

I think the combos will be around 280 for the MMM with the 2200 motor.