ok. i want some SERIOUS advice
 

im building a e-revo, with a motor mount and CD custom made by MetalMan (just like his) and stock diffs. i really want to use the MM esc because my LHS still has the old one (itll run 5s!!) this rig will be about 8-8.5 lbs with batts (trueRC 4s 4000mAh packs, or 5s 4000mAh packs) id like lots of power, good availability, lightweight, and a price of under $350 or so. i am in the US, so its hard to get a plettenberg, but i like the lehner 1930/40 series alot, because of price and weight..... brians speed calc says i need a kv of around 1100-1700 with the CD instead of tranny unless i run super low gearing (it recommends the 1930/9 with 10/46 gearing! :gasp::surprised: if you know of a great motor, that i can get fairly easily, please LMK!

can you post the specifications? that's a slow turning motor with a high gearing ratio! Something must be wrong here.

specs of what?

the speedcalculator results.

Please post them..

Here's what I came up with:

Vehicle Weight (approx): 10
Desired top speed in MPH: 40
Differential Ratio: 2.8461538461538462
Transmission Ratio: 2.2
Additional Ratio: 1
Spur Tooth Count: 40
Pinion Tooth Count: 20
Battery Voltage: 14
Tire Diameter (inches): 6
Total Ratio: 12.52308 : 1
Tire Circumference: 18.85 inches (478.779 mm)
Required Motor RPM: 28062.983 RPM
Required Motor KV: 2004.499 RPM/V
Good Motor Choices: BK Wanderer 9 XL (kv=1853)
BK Wanderer 8 XL (kv=2084)

Better Motor Choices: No motors of this class fit the parameters you entered.
Best Motor Choices: Neu 1515 1y (kv=2200)
Neu 1512 2.5d (kv=2000)
Neu 1512 1.5y (kv=1900)
LMT 1940/9 (kv=1742)
LMT 1940/8 (kv=1959)
LMT 1940/7 (kv=2239)
Neu 1521 1.5d (kv=1860)
LMT 1950/7 (kv=1867)
LMT 1950/6 (kv=2178)

12:1 FDR? that does sound rather high for a large MT type vehicle- and only 28,000rpms on 12cells. Im no expert, but that sound like an under powered & overgeared setup... I could be wrong though.

Yeah, I think that FDR is abit high too. Also, look at the total motor speed in MM's post; 28k rpm. You'd need to gear up pretty high to get the speed you want with that motor speed. I would suggest going with higher voltage or slightly higher kv motor to get rpms in the 35k range. Then you'll see you won't need such high gearing.

Well, since I own Metalman's old revo with the sliper/diff setup I may be of some help.

Now I have one issue, the motor that Mailman sent me is supposed to be a 7xl, but according to BrianG's calc and my radar tests it must be an 8xl. In any case here is the speed calc with an 8xl and 46/20 gearing:

Differential Ratio: 2.8461538461538462
Transmission Ratio: 2.2
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 20
Total Voltage: 14.8
Motor KV: 2084
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0073
Spur/Pinion Ratio: 2.3 : 1
Total Ratio: 14.40154 : 1
Tire Circumference (inches): 18.06 inches (458.83mm)
Total Motor Speed: 30843.2 RPM
Vehicle Speed: 36.64 MPH (58.85km/h)
Effective Speed Rate: 2.48mph/V (3.98kmh/V)
Effective KV Value: 2084
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...

I am currently running 40/20 gearing and while the motor stays cool, the mm is very hot, as are the 5k batts I am using. The 46/20 kept everything much cooler. The lehner 1950 may be able to handle the higher gearing better than the feigao. I have had Griffinrn mod a mm for me and I need to install it and see how it does with this combo. I also have a pair of 4000 14.8 lipos to replace my pair of 2s 5k lipos. So 8k mah compared to 5k should help with batt temps. It is a good setup and the slipper/diff make the steering very good. Also has a low CG, so it is more stable.

Hi lincpimp
I ordered the 7XL - starluckrc may have sent me the wrong one. I think the KV rating is marked on the enbell. 2084kv for the 8XL and 2382kv for the 7XL. I never paid attention to it when I got it - I just assumed they sent me the right one.

IIRC it is labeled as a 7xl, but I could only get 36-37mph out of it so the calc seems to think it is an 8xl. I have a 7xl in my terror, so I may swap out and try it. Not sure why the mm gets so hot and the motor stays cooler?

correct me if i am wrong, but the true RC 4000s have 40 continuous amp draw. Isn't that a little low for a setup like this.

E-revo at 8-8.5lbs:surprised: ggggggggggggoooooodd lck man

9.5 lbs is the lowest without going to extreme measures to reduce weight... and power.

Is that RTR or without the batteries? :whistle:

Dan's Cells are not over rated and as long as you don't get your hands on some cheap 10C China cells that are over rated, You might be surprised what 10C can do.

The 4000mah 10C cells are pretty strong. I have several packs that I've ran in my E maxx pretty much all summer. A 6S1P 4000mah setup pushed it past 50mph several times.

One of my favorite E maxx setups has been the 4S 4000mah 10C setup. Weight for both packs is like 14 ounces. Lighter is better in alot of ways.

How many Amps you're going to draw from your packs really depends on motor choice, gearing and vehicle weight. 40 amps continous, 60 amp burst is respectible depending on your setup.

Remember the days of Nimh? The best of them today can't beat that, especially since they're twice as heavy.

The 10C choice is a good decision IMO, IF you're not running a super HOT setup that pulls 100 amps. Even then, I have some 10,000mah 7.4v Lipo packs made from 5000mah 10C cells (2S2P) that will go 100 amps continous.

For HOT, High amp draw, lightweight setups, a higher "C" rating is the way to go. But for the mid stream, and low end applications, the 10C is more economical.

Completely RTR. :yes:

OMG! I have alot of trimming to do. Mine weighs 9.5 pounds without batteries. :lol:

Time to swiss cheese the batery mounts and the esc mount. You have alot of al on that truck, not a bad thing though!

well i found a new kind of lipo today, known as hextronic. available at www.hobbycity.com and is about the same price as truerc. better or worse in your guys's opinion?

With the Revo that Lincpimp has now, I ran a 7XL on 5s2p A123 with 20/46 pinion/spur. It had plenty of power, and 40mph top speed was enough for me. The 7XL ran at a good temp, but as Lincpimp noted, the MM runs hot.

Yeah, I found that the 7XL has loads (s**t loads) of power on 5s2p, but it also takes s**t loads (huge s**t loads) of power from the battery. Drawing 135amps consistently.

ooooh! you cussssssssssseeeeeeeeeeddddddd iiiiimmm teeeeellllllling! :lol:

I too have the TrueRC 4K cells, but in an 8K pack. I think 4K is too small. I think the motor you are looking at is a bit small too. A 1940 at a min. A 1940/7 on 4S would be great. The MM may or may not like 5S, I wouldn't bank the setup on it.

You should be getting ~120A peaks, which is alot for a 40A continuous cell. Driving is very peaky, and I think you will overdraw and heat up the cells. If you really want low weight you got to pony up a bit. I'd at least get the 5K cells if you are determined to stay cheap and 1P

You little tattle tailer!! :na:

hahahaa

Actually, no one tattled, but I saw the response and just HAD to edit it for you. No extra charge. :tongue: :lol:

Geez Brian, you always got my back! :angel: