Starting work on a basher e-jato

[olds97_lss]

I've had a 2.5 jato for a long time, at least 10 years. That's the oldest photo I have. Tried selling it a few months back, but nothing but low ball offers. So, now that I'm seasoned vet with electric (5 whole months), I decided to try converting it to brushless.

I'm using the motor/esc from my stampede 4x4 vxl. Figure 2wd will make it less likely to overheat. Especially since I'm going to try 2S.

Upon taking it apart, I noticed the trans was really notchy/gritty feeling. I needed to put a single speed conversion in it anyway, so I tore it all apart. Then found that one of the two-speed pins broke off and had it's way with pretty much every gear in there:

As for the e-conversion "kit", I bought it off ebay and it came with just the mount and esc/receiver/battery tray from a guy that makes them in Greece. Fit and finish was pretty good. It's a very solid well machined hunk of aluminum. It screws to the trans where the stock plastic brace did and bolts to the chassis near it's front edge to a stock screw hole. I liked that the mount had at least one bolt to the chassis to stiffen things up a bit since pretty much the entire top deck was cut off. I did have to grind a little spot because the slipper cooling fin hit it and wouldn't rotate:

I just kind of have everything sitting in there. I did drill and tap one of the esc mount screws. The receiver is literally wedged in there. I have a new smaller receiver coming in the mail with a bipole antenna as well as a replacement diff.

I also have a 20T pinion coming. I put a 17T in there just to see how it fit. I have no idea what gearing to use. For what I do, with the 2.5R, I ran relatively low gearing and it was plenty fast, 18/54. It seems that 17/54 doesn't fit, so I ground a hair off the trans to get it to mesh. The single speed trans is geared between what it had with 1st/2nd. Running 2S at full charge and a 3500kv motor will put peak rpm's right at 30k. Guessing I'll be playing around with gearing a bit.

I'll need to figure something out for the roll bar though. One of my main issues with the jato when I first got it was I'd frequently snap the rear shock tower off. I made a roll bar that kind of protected it, but it also connected to the stock roll bar. Many hours were burned making this thing with a vice, torch and pliers. Sooo many bends...

It has done it's job well for many years and fit nicely under the body. As it is, the shock tower in it has one side cracked that I didn't know about and that was the first one In installed with the roll bar. Prior to that, I had replaced 6 or 7 of them. So, figuring something out is a must.

When the diff and whatnot all show up, I'll hopefully have thought out a way to mount my roll bar on. Will probably have to make something out of some steel flat stock and mount it to the chassis deck somewhere. Not a whole lot of room for things with the battery right where I'd want to mount a roll bar. I'll post up more pics when I get it finished.

 

[olds97_lss]

Well, ran half a pack through it last night as a test. Using 54/20 spur/pinion and 2S. Seemed pretty quick and pulled easy wheelies.

Worked on making a support for the rear tower since I couldn't figure out a good way to mount a hoop/roll bar to it with the battery in the way. Hoping a little bracing will help extend the life of it. I just put in a 6mm post, drilled/tapped the bottom for 4mm countersunk screw and the top for 3mm, then ran a steel bar from a plate I made on the rear tower. I didn't connect it to the front chassis upper deck, I figured with it sitting right against it, any force bending the post would push into the chassis deck. Since the chassis deck is more or less floating now, I didn't want to rely on just screwing to it and figured a post was my best option.

Still waiting on the new receiver. May throw the spektrum in a ballon and tape it up so I can velcro it down for now. I don't get near the range out of it as I do the aftermarket ones.

Now I need to clean up my work bench... looks like a bomb went off.

 

[olds97_lss]

Got a little bit of video of it today:
https://www.rcnitrotalk.com/forum/threads/my-latest-bashing-vids.113919/#post-1111968

Only made it 10 minutes into my run and the single speed conversion gear spit out it's teeth. I've ordered a hot racing steel single speed conversion which replaces all gears except the large diff gear. Hoping that holds up just due to it's size, more plastic can take more abuse. Also ordered a set of traxxas steel cvd's. Couldn't find MIP's still available and from what I read, Traxxas makes the better ones anyway.

 

[Certified Mike]

So, while I have been working on my revo trans, I have run into an issue. I have never taken the trans apart before and bought it new so everything in there is stock and def has low hours. It seems my bearings are very difficult to remove and even more difficult to reinstall... Did you or have you run into similar and what did you do to resolve? Is this just an issue of cheap bearings from the factory and I should just replace them all? Any input would be appreciated.

 

[olds97_lss]

It's more the tight tolerances of the case. That issue is really bad with an alloy case, sometimes requires heating the case to get it to expand and freezing the bearings to get them to shrink, then installing quickly. For getting them out, the best you can do is just pry at them at an angle from the inner race with a fine point needle noes pliers that has teeth in the jaw, so the last tooth on the tip can grab under the race. Then you just gently pry from one side of the race, then pry from the other to kind of rock the bearing out. That's with bearing seats that completely block the back side of the, bearing. There are a few like that in the transmission housing. Pretty sure both ends of the 2 speed shaft are like that. For the others, you can usually push them out from the other side of the case by using a tool that tapers so your pushing on the inside of the bearing race.

To get them installed, the best you can do is make sure the case is clean, put the bearing as flat as you can, then put a flat dowel end on it and gently tap it with a hammer to get it to seat.

 

[Certified Mike]

I was afraid you might say that. I haven't had much issue with the outers going into location but the inner races just s to want to grab what they are on or going on and don't want to let go. I have tried all sorts of tricks... I will figure out something that works. Blah!!!

 

[olds97_lss]

Got the hot racing steel single speed conversion installed. Also installed a set of traxxas cvd's. Those tiny e-clips inside the diff were a pain.

Oddly, only got about 35 minutes out of my SMC 9000mah 2S 60C pack. When offroad, I got 27 minutes. Was kind of surprised by that. I get 25-26M in my stampede 4x4 with SMC 7200mah 2S 120C packs. I expected a lot more out of the 9000mah packs. At the skatepark, my motor/esc temps weren't bad. The ESC was about 20F higher than the motor. Was the same when running offroad. Motor got to 130-140, the ESC got up to 150. Maybe I'm geared a little too high for offroad. With 54/20, it's considerably faster than the stampede. Will probably order a 19T pinion to avoid overheating it during long bash sessions. Carrying the 9000mah pack probably isn't helping either. Or the hunk of steel plate and bar I put in for the rear tower... or the steel FOC. LOL!

The 9000mah pack doesn't fit that great. I would like it if it was about 10mm shorter. As it is, I have to flex the chassis pan skirts a bit to drop the pack in, then they hug both ends of the pack. I ordered a couple more 7200 and SMC's new 9500 packs. The new 9500's are a higher C rating than the 9000's and are a bit smaller per the specs. I have to wait for SMC to get 7200's back in stock before they ship me my order though. Hoping I get them before Memorial Day weekend.

With the 2 packs, I ran it very hard for almost a solid hour without any failures.

Latest vid from today: https://www.rcnitrotalk.com/forum/threads/my-latest-bashing-vids.113919/page-2#post-1112208

 

[olds97_lss]

Latest from today:
https://www.rcnitrotalk.com/forum/threads/my-latest-bashing-vids.113919/page-2#post-1112596

Got my new receiver installed. Now I can actually open it up and have some fun!

 

[olds97_lss]

I've now run both the SMC 7200mah 90C 2S and SMC 9000mah 60C 2S packs in the ejato. I get nearly the same run time, only 3-4 minutes less with the 7200's. I ran in the exact same area and drove it exactly the same. The only things I noticed was that it was a bit more punchy throughout the entire run and it did slap the ground as hard with the 7200's.

 

[olds97_lss]

Got a few updates. Busted a rear RPM arm in my last outing, so I replaced that with a new set of black RPM arms.

After running it so much lately, it really drags it's rear on the ground a lot, especially when hitting jumps and whatnot. Also makes it not go so great in the grass and it wants to float. So, while I was replacing the rear arms, I tried to figure out a way to eek a bit more height out of the rear. What I came up with was to use savage shock ends. They fit the revo shocks I have on there pretty well, but I did have to grind them down a lot to fit the spring cups. The savage shock ends were about 3mm longer than the revo ones, which added a decent amount of hight in the rear. The chassis still bottoms out before the shocks do, just barely.

I ran it for 5-10 minutes in my parking lot and the courtyard grass. It seems to move around a lot better. I don't have any jumps, so I wasn't able to see how it did with that.

Today I just got a t-bones front skid. I busted the RPM bumper/skid, so figured I'd give t-bones a shot. I had to cut some of it off because the tires hit it when turning. I also drilled a couple holes and put a couple more screws through it to screw it to the stock bumper to add some support.

 

[olds97_lss]

Latest video found here: https://www.rcnitrotalk.com/forum/threads/my-latest-bashing-vids.113919/page-2#post-1112899

 

[olds97_lss]

Some updates...

2018/05/17 - Better tires a year later:

2018/09/19 - Castle 3800 after smoking the traxxas 3500:

2018/11/03 - Found a front brace:

2018/11/03 - Built some 3S lipo's out of 2S ones I had:

2019/02/11 - Increased rear ride height with dubro 2319 rod ends on the shocks, also installed hard anno'd/teflon coated/tini shocks with VG dual rate springs and drilled out VDK pistons to 1/16" and 80wt oil (I think):

Still bottoms out before the shocks do:

2019/03/27 - Got some 15mm extensions so the rear was closer to the front in width:

2019/03/29 - New motor, hobbystar 3660 3300kv:

 

[olds97_lss]

The esc was acting weird the last time I ran it and I forgot about it. Was reminded when I ran it again recently. It would hesitate from 1/4-3/4 throttle when I punched it to launch a ramp or accelerate. Not sure why. I crashed it and busted a rear RPM arm which I'm waiting for, so I decided to put a spare max10 sct esc and hobbystar 3665 3100kv motor in it while I wait. Also bumped the gearing up a bit to compensate for the lower kv from 58/18 to 58/20. I didn't have a 19T.

Video from last weekend with the vxl-3s in it:

I showed the cutting out in a couple places, 16 - 19 seconds was the first instance. Guessing the new motor/esc eliminates the issue as I never had that when I ran the system in my stampede 4x4. Pretty sure it's not the lipo's as I'm running the same 3S 50C hobbystar 6200mah packs I use in my 6S trucks and stampede with a blx185/2200kv system in it without issue.

I forget how fun the eJato is until I take it out. Only works well in short grass or at the skate park though. Would be fun at the grass bmx track I run it, but the grass there is usually too long and it spends most of it's time just spinning the wheels.

 

[olds97_lss]

The esc swap did fix the hesitation issues I was having. And a new set of rear tires gave me good grip on the grass at the bmx track I run at:

My last run with it last year at the bmx track:

I'll be running 4S on it next year, so will need to drop the gearing a bit. I'm running 4S in my stampede 4x4 now and the packs I use in it, I also use in the eJato. Should be amusing...