RCM Available gears

[Batfish]

Originally Posted by BrianG

Thanks "Joe". :) I read some of that thread and I didn't see where it said why the motor mount on the chassis didn't work. I would think the mount on the tranny would be far weaker, but I wouldn't dream of second-guessing someone who went through 3 versions of a Jato! :) Did that Lehner Basic 4200 get hot? Any idea how much amperage the motor drew on average and pulse? I wanted to see the videos you had, but the they were removed or something. :(

Two reasons for the motor mount on the chassis not working for me.
1 - Weight distribution. It kept too much weight in the front of the vehicle, which was no good for racing. Aside from testing in my back yard, the only way I used the Jato was on a race track.
2 - Design. The "L" mount I made was held in using the nitro engine mount holes with a couple of weak post/hole screws that just kept moving.

Considering the tranny had those two convenient screw holes and the mount got the motor up (so I could move the batteries back) it was the next logical step, and the best one. That mount held the motor just fine for a couple months and about 20 races. It never broke or bent - it just went to coolhand :003:

I used a basic XL4200, not a basic 4200. The XL4200 never heated up in the tests and running I did...maybe 120F tops, if I remember right. When I was using the MGM 12012, that never got warm. When I used the MGM 8012, that got over 110F a couple times, but never hot enough to be concerned. Although I can't tell you definitively how many amps it was pulling, I can say that the last few times I ran the V3 it pulled on my unmatched GP3300 packs hard enough that they came out of the truck at 120F or more after a 5-minute qualifier, and my IB3600 packs would just barely make a 6-minute main, also coming out plenty warm. The electronics remained warm/cool, so I wasn't concerned about hurting them.

By the way, "Joe" has been in my signature for well over a year :dft012:

[RC-Monster Mike]

40k rpms isn't so much an efficiency limit, Brian. It is just that higher rpms yields higher amp draw and higher heat in almost all cases. This includes the speed controllers, which have to "think" at the motor rpm to keep time. 30k to 40k is a nice place to be - plenty of rpm to have smooth control and a wide range of gearing options to tune, along with decreased chance of overheating or motor damage(if you scream the motor at 65k rpms and jam the brakes with a heavy truck in a high traction situation, the speed controller will hate you, and you risk throwing the magnet on the motor - better to keep things on the safe side IMO).

[BrianG]

Batfish: Cool, thanks. I was just a little skeptical that those little clutch guard screws would hold a motor mount. I think I'll still try an L bracket, but won't use the Nitro mounting holes, but make two or three new 4mm holes. This won't be for track use, but more for parking lot/driveway/sidestreet use, so I'm shooting for a 60/40 weight distribution.

So, it looks like I may want to stick with NiMH cells for the current draw. The e-molis I have are lighter, but they only like 10C discharge rates, 15c if you don't mind the dropped voltage. I suppose I could go with 2s2p instead of 3s, but that adds weight - however, it would give me 6Ah. Your IB 3600's lasting 6 minutes equates out to an average 36A draw. A bit higher than I was hoping for such a small/light vehicle. With a similar setup, 6Ah would give me a whopping 10 minute runtime. Oh well.

And about your sig: I'm sure I read your posts dozens of times, but I don't remember names well. :)


Mike: Thanks for the info. I thought maybe the LMTs or Lehner Basics might stay cooler at higher rpm compared to the "lower-end" Wanderers due to better bearings.

[RC-Monster Mike]

The Lehners will run a little cooler than the feigaos. A lot depends on how you use it as well. If your just bashing around, you likely won't have extreme heat with the lesser motors. If you plan on long races on a track, the Lehner "19" series is the answer.

[BrianG]

Originally Posted by RC-Monster Mike

The Lehners will run a little cooler than the feigaos. A lot depends on how you use it as well. If your just bashing around, you likely won't have extreme heat with the lesser motors. If you plan on long races on a track, the Lehner "19" series is the answer.

I was looking at the 1920's you do have in stock and thought maybe one of them will work if I can rearrange the windings for a higher turns ratio. Before this is done, will the various speed controllers (BK, Quark, Castle) be able to hook up to wye configurations? All the inrunner motors I know of are delta wired, so I don't know if the ESCs can properly drive and read wye configs. Also, do you have the formulas and such for re-wiring them? I think I had found a document explaining this at the bk-electronics website, but they have since re-structured it and I can't find it now.

[coolhandcountry]

The formua is the amount of turns multiplied by1.7. It you have a 10 tunr and change it to a 17 turn. If that helps you any.

[BrianG]

Originally Posted by coolhandcountry

The formua is the amount of turns multiplied by1.7. It you have a 10 tunr and change it to a 17 turn. If that helps you any.

Yes, that does. So, I assume then it also divides the kv by 1.7? How about the question I had asking if all ESCs can use the wye configuration?

[neweuser]

There is also another guy on the traxxas forums that converted a jato, if you wanted to look at that one as well. i know this does not answer your above question, but thought it could be useful.

[squeeforever]

Brian, I'm pretty sure that all controllers can run a motor in wye configuration.

[BrianG]

I got tired of trying to find a motor for a semi-high voltage setup (11.1v) while maintaining relatively low currents (~30A), so I changed my e-moli cell pack from 3s1p to 2s2p. Now I have 60-90A to work with at 7.4v instead, which should allow me to look at the higher kv motors like the 1920/7. According to the LMT site, this motor draws up to ~62A.

[coolhandcountry]

The 62 amp draw for the lehner motor is the maxximum efficency amp draw. So it may draw more. It may draw less. Read that on the lehner site.

[BrianG]

I figure it's a good starting point. The e-molis work good up to 10c, then drop their voltage at 15c. Plus, if I get the Mamba, I can set the torque curve so it's a little easier of the batteries and drivetrain.