On-road BL project

[BrianG]

Batfish: I read in the Jato area where you did a Jato conversion. Got any pictures? Did you do the single speed conversion, and if so, does it allow you to use ESC brake and reverse?

[Batfish]

Originally Posted by BrianG

Batfish: I read in the Jato area where you did a Jato conversion. Got any pictures? Did you do the single speed conversion, and if so, does it allow you to use ESC brake and reverse?

The Jato transmission has a one-way bearing in the first gear, which does not allow the use of reverse by default. I did not do the single speed conversion.
I originally ran the truck with a servo for the mechanical brakes. In the second configuration, I locked the transmission into second gear, which bypassed the one-way bearing in first gear and allowed me to use the ESC for braking. In the third (and final) configuration, I unlocked 2nd gear and added a servo again for mechanical brakes.
If you want to do some custom work inside the transmission, I'm sure you can get it set up to use the ESC for braking.

[BrianG]

Thanks. Sounds like you have a bit of experience with the Jato tranny. :)

I looked at the Jato's exploded views and I see the OWB on the first gear you are talking about (similar to the Revo actually). There is a single gear conversion for it, but it's probably the equivalent of first gear more or less, but it does look like it does away with the OWB without further mods.

What motor would push it well for high torque, high speeds, without heating up? I would think a 540 "S" size? Or is an "L" can a better choice? I'm not sure how much it weighs, but it can't be too heavy especially since it's only 2wd. As you can imagine, I'll be using lower voltage, probably 2s or 3s lipos (maybe even E-Molis). How does the rest of the drive train hold up under BL?

[BrianG]

So, does anyone know of a good motor to use in a Jato conversion? Like I said above, cool running, high torque, and hi speed are desired. Then again, being 2wd, too much toque will tear stuff apart, so I dunno. Cell count is flexible. Would an "S" motor be too small and run hot, or should I go with an 9L or something?

[Batfish]

Originally Posted by BrianG

So, does anyone know of a good motor to use in a Jato conversion? Like I said above, cool running, high torque, and hi speed are desired. Then again, being 2wd, too much toque will tear stuff apart, so I dunno. Cell count is flexible. Would an "S" motor be too small and run hot, or should I go with an 9L or something?

I used a Lehner Basic XL4200 in my Jato. That, with an MGM 12012 and 2s lipo is what got me 37MPH on my street. That was the only time I checked the speed. That setup ran nice and cool.

I also played a little in my back yard with 3s lipo, but never measured the speed. The drivetrain held up to 3s lipo for at least the 15 minutes I ran it :003:

In the regular use of my converted Jato (racing) I ran 6-cell nimh packs with an MGM 8012 and the XL4200, and never had a problem with the drivetrain or heat.

[MetalMan]

How about a Mamba Max? It should work very well. Based on what Batfish used, the Mamba Max with the 4600 motor should work excellently.

[Batfish]

One other note for you with the Jato - the Mod .8 spur gear that Traxxas uses on the Jato meshes up with standard 32 pitch pinions just fine. I ran regular Robinson 32 pitch pinions on a 48T Mod .8 Jato spur for 3 months with no noticeable wear.
If you wanted to go to Mod 1, the Revo spurs bolt right on to the Jato slipper assembly. It reduces your gearing options overall, but does give you the ability to easily use Mod 1 if you want.

Yet another Mod 1 option is the Associated MGT spur gears. The slipper peg holes line up with the 3 slipper screws for the Jato. This spur will stick out a little further than the stock spurs, so make sure your motor shaft is long enough and the pinion will reach. This option does require two modifications, though. First, the center hole has to be shaved out a tiny bit (maybe 1mm - I did it with my dremel and a sanding wheel) to accomodate the bearing it rides on. Second, one of the screws that hold the rock guard comes up right under the spur gear and will interfere with any gear larger than the stock Jato 48T. If you remove/relocate that screw and cut off the plastic nub, you can use a larger spur.

[MetalMan]

I used a MGT spur gear on a Revo slipper clutch unit for quite a while. If you have a 5mm drill bit, you can bore out 3 of the wholes (triangle pattern) on the slipper clutch plate and the spur gear is a nice tight fit - that doesn't stick out far.

[BrianG]

Thanks guys. I have a place to start.

Batfish: Yeah, I figured the Jato used 32p teeth from parts in the stores. Not sure yet if I want to stick with that or go Mod1. I guess I'll have to pick up a Jato roller and go from there. I plan on coverting to single speed and use motor brake, so tranny work will be in order. While I'm at it, I'dd do any kind of drivetrain mods I can. To get better runtimes (and less current draw),, I was thinking of a slower motor, using 4s E-Molis and gearing it up, something like a XLBasic 2400?

MetalMan; The Mamba Max package does look like it would work, and relatively cheap too. Seeing the picture, those motors look to be an "S" can, is that right? With a kv of 4600, that's a 6 or 7 turn right? That's gonna suck quite a bit of current too I'm assuming. If I decide to do low cell counts, that will work fine. I'd like a bit more runtime though...

Sorry for all the newb-like questions. I've done two Revo conversions and both are relatively heavy trucks, have quite decent drivetrains, and have room for basically any reasonable amount of cells. The Jato is lighter and only 2wd, so probably has a not-so-robust drivetrain. So, I don't want to throw too much power into it and wreck everthing - then again, I DO want insane speeds (~50mph for me is insane) :)

[squeeforever]

I would go for a 1920 if you can. That would be the ultimate motor for a small light weight truck.

Brian, was that your E-Revo on ebay?

[Batfish]

Originally Posted by BrianG

The Jato is lighter and only 2wd, so probably has a not-so-robust drivetrain. So, I don't want to throw too much power into it and wreck everthing - then again, I DO want insane speeds (~50mph for me is insane) :)

Stock 2-speed with a xl4200 and 3s lipo is right around 50mph with a 21t 32p pinion. I can say that the Jato's drivetrain is pretty strong and not at all loose, but it is all plastic gears so you can only put so much torque through it before they start stripping.
It's also nice that the rear axle diff is a geared diff instead of a ball diff. Ball diffs have a harder time coping with large amounts of torque.

[MetalMan]

Just to add this, the XL4200 and the MM 4600 motors should draw about the same current, the 4600 a slight bit more.
If you go by Feigao's turns, the 4600 could be like the loaded kv of a 7s.

The only way to get longer runtimes is to get batteries with higher capacity (Lipo) or go with higher voltage. For higher voltage, extra NiMh cells would add extra unnecessary weight - Lipo's the option for high voltage as well. For 6 NiMh cells, you're going to have a bit of a hard time coming by a motor that's powerful enough yet light enough at the same time - a Feigao 380C 6L would probably be the best choice for 380 motors (and that has a similar kv to the MM 4600 motor).

[BrianG]

Squee: Yeah, that's my E-Revo (v1) on Ebay. I like V2 much better so I'm keeping that one. Just curious, what is a good and fair price for something like that? The proceeds from this sale will be going to the purchase of a good Lithium charger and batteries for V2 Revo.

Batfish: I'm glad the tranny and diff is strong. Like the title says, it will be for on-road use only, so it won't be subjected to the same rigors as a normal MT or buggy. Once I get the roller and get a feel for its structural strength/weight/etc, I'll have a better idea if I want to go with 3s or 4s and then an appropriate motor. I know enough of BL to know the relationship be and power. I'm leaning to a slower turning motor at higher voltage, but that depends on the physical space on the truck and the weight.

MetalMan: Feigao's chart is what I'm using to get a rough idea of the kv vs turns ratio and therefore, current draw. I'm hoping that by using higher voltage and less vehicle weight, I can keep current draw to ~80A peaks with ~20A (or less) average current draw. I figure the E-Molis might be a good pick for this. I know and realize that e-molis drop voltage after 30A or so, and I'm actually counting on this a little to help keep the "punch" down a little on take-off to protect the drivetrain.

Thanks for the assistance! Once I get going with this project, I'll post back with my progress and pics...

[Batfish]

Originally Posted by BrianG

Batfish: I'm glad the tranny and diff is strong. Like the title says, it will be for on-road use only, so it won't be subjected to the same rigors as a normal MT or buggy. Once I get the roller and get a feel for its structural strength/weight/etc, I'll have a better idea if I want to go with 3s or 4s and then an appropriate motor. I know enough of BL to know the relationship be and power. I'm leaning to a slower turning motor at higher voltage, but that depends on the physical space on the truck and the weight.

Just keep in mind that on-road applications typically have much more traction than off-road. This extra traction can actually be more harmful to a drivetrain than slipping in the dirt off-road.

[BrianG]

Originally Posted by Batfish

Just keep in mind that on-road applications typically have much more traction than off-road. This extra traction can actually be more harmful to a drivetrain than slipping in the dirt off-road.

Good point.