RCM Available gears
 

I'm trying to figure out what gear set I want to use on my E-Jato project. I'm not sure if I want to go with Mod 1 or stay with 0.8 pitch. Mod 1 has thicker teeth for durability, but the Jato is so light, I don't think that will be an issue.

Anyway, the problem I can see is that the transmission doesn't leave much room for a variety of gearing options. So, I need a fairly large spur. The Revo spurs go as high as 40T, but are not very big around. So, I need a large pinion to give me the room I need. Besides, I want a spur-to-pinion ratio of about 2.2:1 or 2.3:1. At 40T, that's an 18T pinion, which aren't available for Mod 1.

Soooo, I figure I'll stick with 32p. If I stay with the 54T spur, I need a 23T or 24T pinion, which also aren't available.

I can't go with a smaller spur because then I get tranny clearance issues between the motor and tranny.

Argg. Any other ideas?

Mike sells 18t Mod 1 pinions, and they're in stock.

You can run a 32pitch pinion on the .8m pitch spur. If that helps you out any.

mike might be able to make you something:032:

Brian, are we talking 1/8th inch shaft? If so, that shouldn't be much of a problem. Even then, contact Mike, he can get larger pinions than are in the store.

Aah, now I see; they weren't in numerical order. My bad. So it looks like I'll be going with mod 1 gearing., as long as the motor I select uses a 5mm bore. That negates the use of the Mamba Max systems because there are no 1.8" bore Mod1 pinions above 15T, and I would need 18T. I also have to watch the size of the gears to make sure they are big enough so the motor will clear the tranny.

Edit I took so long to post my response that two oither posts came in! I guess I'll have to figure out what motor/ESC I'm gonna use and then pick my gearing based on that. Once I decide, I might have to ask Mike if he can make/get the right size. Thanks guys.

You may have to make sure the spur gear will fit on the trans as well. I think my jato has a 40 tooth jato spur on it. It was run with a 32 pitch pinion with no wear. 15 tooth pinion with 40 tooth spur 40000 rpm 2 speed trans is like 50 mph. That is not fast enough. Or you want faster?

The Jato has a 54T, 56T, and 58T spurs available in 32p. If you use Revo spurs, which are Mod 1, you have 36T, 38T, and 40T. Revo spurs do fit.

I'll list a few gears and their diameters to make my next argument easier:

Mod1
- 40T = 42.67mmD
- 38T = 40.53mmD
- 36T = 38.40mmD
- 20T = 21.33mmD
- 18T = 19.20mmD
- 16T = 17.07mmD
- 14T = 14.93mmD

32p
- 58T = 48.33mmD
- 56T = 46.66mmD
- 54T = 45.00mmD
- 22T = 18.33mmD
- 18T = 15.00mmD

Purely for sizing purposes, I lined up an 8XL motor (just to guage the clearance between the motor and the tranny using real parts) with a 14T mod1 pinion with a 54T 32p spur. The clearance is VERY close, but do-able. So, I added the two diameters together and divided by two to get the distance from the tranny shaft to the motor shaft, which is about 31mm. So, no matter which gear set I choose, I have to have at least 31mm between the two shafts or the motor will hit the tranny.

Now, a little info about my Jato. I did the single speed conversion, which has a ratio in between 1st and 2nd. If I use the stock spur/clutchbell ratio, 3s Li batts, and the BK 10S motor, I get about 45mph. A little slow, but I didn't factor a couple things. So, I want to keep the spur/pinion ratio the same or lower for equal or more speed. 54T/22T is 2.45:1. Using a 40T, that means I would need to use at least 18T to get the same ratio and keep a safe diameter. I can't use anything larger than a 54T 32p spur because the rear a-arm could conceivably hit the spur under certain conditions (although unlikely).

So, long story short:
Using 32p, I need 54T spur and 22T+ pinion.
Using Mod 1, I need 40T spur and 18T+ pinion.

Then, aside from all of this, I have to make sure the pinion I select is available in the shaft bore I need. Ugg.

Sorry I have a 58 tooth spur.
But the .8m pitch and 32 pitch will work together if you worried. May help may not.

Brian, If I were you, I would choose the Mamba Maxx controller with a different motor depending on what shaft you want.

CHC: Actually that does help. I wonder what the "32" in 32p stands for? I know the "0.8" is metric (in mm), but it doesn't mean anything if I convert it to standard...

Squee: Yeah, that controller seems like it will fit the bill. I especially like the fact you can program your desired torque curve! That will save the tranny and diff and help runtime! Plus, I'm using 3s e-molis and I want to keep the current down somewhat.

I was thinking about the BK 10s. Does the S series have enough torque to get a 5lb truck moving without going over 130 degrees?

I would think it should. Just remember, its got a 5mm shaft. My personal choice would be a Lehner 1920.

Here's a good link for seeing the equivalents, if not how they actually convert. I don't understand most of the terminology, however :003:

http://www.engineersedge.com/gear_pitch_chart.htm

Joe is the one that hooked me up on the info. He should know. :D

The "32" in a standard 32 pitch gear is known as the diametral pitch. Pretty sure this means there are 32 teeth per inch(diameter). 48 pitch would have 48 teeth around a 1 inch diameter. Same idea as the metric sizes, just uses inches (mod1 - tooth count = mm pitch diameter, so a 51 tooth mod1 one gear has a 51mm pitch diameter). This is handy information of you are drawing a part that needs gears to mesh.

I am quite sure the Castle controller will perform quite well. They obviously spent a lot of time developing it. ;)

The BK10s has plenty of snot, but pretty much all the Feigao based motors will run on the warm side in a car. I agree with Squee on this one - Go Lehner or go home. :) The "s" motors have a 1/8" shaft unless otherwise noted.
Th Neu motors are quite nice as well, though the ends are open(good for cooling-bad for harsh environments).

Also... LMK what gears you need, Brian. I can easily make an 18 tooth mod1 pinion in 1/8" bore if that is what you need. :)

That pitch chart and explanation is great! Thanks.

So Mike, when you say "Lehner", which do you mean? The basics or the LMTs? Yeah, I don't like to use any motor with exposed insides - too much risk of getting crap inside.

Mike, I thought all the Wanderers have 5mm shafts??

I was referring to the "19" series motors, Brian. The basic series is a step above the wanderer/Feigaos, but 2 steps below the "19" series in terms of real world efficiency in a car/truck application.
Squee...I get the "s" wanderers with a 1/8" shaft - 5mm doesn't make sense in the small vehicles these are likely to work well in, as gear selection would be a giant PITA. :)

Hmm. I was afraid of that. I'm sure those 19 series motors are very nice, but man are they expensive! Seems almost a shame to use one in a Jato.

For the sake of argument; based on the fact I'm using this motor on a Jato (~4 lbs fully loaded), using 3s E-Moli Li cells, what is a good turn motor to get? I want speed (about 3100 rpm/v), but I also need to be careful about current draw since the e-moli cells are only good for 10-15c tops. Maybe a 1920/9? Also, I just noticed you don't even have 1920's.

I DO like the fact that they are efficient and stay cool though, and are lighter.

I have a jato in the making as well. I going to try it with a couple different motors. I am leaning to a 4s lipo oand a 12s feigao. I have esc and motor already. I have a 8s as well. I may try a 380xl in it to. I can give you my report on it.

Yes, please do.

By the way, how are you laying out your components? I didn't like the plastic thing covering the majority of the front end so I made a new upper deck out of 1/16" 6061 Aluminum, which is meant to hold the Rx, steering servo, and ESC. The motor is in the back (obviously), and the batteries just in front of the motor. I still have to make the motor mount, but I think I have what I want to do in mind (thanks to the help here). After calculating the weights of the various parts, the truck should be right around 3.5 lbs (and that's being generous).

WEll I got mine from joe. He had it converted already. I just got to do a little here there and see if it helps or hurts. I have not totally decided yet on everything. The stock plastic plate has been hacked down some on mine. It is light and strong still. I let you know. I am still running a two speed trans with manuel brakes. :D I have a need for speed.

Sorry, Brian. I have a few 1920 motors here, but forgot to activate the listing! No wonder they haven't been selling! :)

I hacked up my plastic part as well until I decided it just wasn't right for me - only about an hour of wasted effort. :rolleyes: As far as two speed tranny, that was the first thing I removed. You'd be surprised, it saves quite a bit of weight. Plus, I wanted reverse. The single speed ratio falls pretty much right in the middle of what the first and second gear ratio was. I figure I can make up the speed with gearing and/or a faster motor. Do you have any pictures? I won't steal any ideas, honest. Just curious how things are laid out and what a BL motor looks like in there. :) What did Joe (is he a forum member?) use for the motor mount? I plan on using some 3-4mm thick angle 6061 aluminum.

Well, don't list them until I get one! :027: How much are they, or are you going to list them?

EDIT: Nevermind, I see you listed them... I take it you don't have any 9T? The 7T will probably suck too much current... If you don't have them, can you get them in a reasonable amount of time?

Joe would be me :003:

You can see the evolution of my Jato conversion at http://www.rc-monster.com/forum/showthread.php?t=957
The V3 with the motor mount on the tranny is what I sent to Leroy (coolhandcountry).
It's a little bit of a read, but if you get through the whole thread you'll see all of the things I did to make it the way it was.

Hope that helps!

Don't forget, Brian...the Lehner motors are kind of "2 in 1". The 6 turn can be reconfigured into the same Kv as a 10 turn. The 7 turn can be reconfigured into the same Kv as a 12 turn. They kind of serve dual purpose in this respect.
By the way...Joe is Batfish on the forums. :)

Whoops. Didn't see your post, Joe. :)

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. :(

Mike: Yeah, I forgot about that. I now remember reading something about that somewhere but I never really understood it. I know you are basically changing the windings from delta to wye configuration, but I didn't get the calculations for the kv/amperage ratings for each configuration. IIRC, the document was translated or something and it wasn't too clear.

EDIT Oh, do the LMT have the same efficiency limit of 40k that the Wanderers do? How amount the Lehner basics?

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:

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).

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.

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.

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?

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.

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

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.