My e-revo brushless edition build

[mistercrash]

I started by modifying the Traxxas TRA5415 and TRA5416 Traxxas output shafts. You cut the gear part off and have to drill a 2.6 mm hole for the spider gear pin. The tricky part is having the hole perfectly centered in the shaft.



Here are two of the TRA3985X Traxxas output gears, you see them with the flat side of the spokes up. The left one is stock and the right one has been drilled in two holes with a 6 mm bit. If you use the Axial posts I linked above, the holes will have to be 7 mm or 9/32 inch. There are two of the gear’s spokes that are thicker than the rest. The holes have to be drilled next to those thick spokes and which side of the spoke you drill is also important. I drilled according to the rotation of the gear inside the tranny, I wanted the forces exerted to the gear to be transferred to the posts from those thick spokes. The center hole has a little ridge that was cut off to allow the 8X12X3.5 bearing to sit a little deeper in the gear.



The two inner threaded aluminum posts that will be screwed to the diff cap. The length on the posts is about half a millimeter less than the thickness of the Traxxas TRA3985X output gear.




Now to start modifying the ring gear. I make the holes and I counter sink them first. To make sure that the holes were in the correct position, I used the Traxxas output gear and aluminum posts as a template. I slipped the two posts in the holes I made in the output gear and the 8X12X3.5 bearing in the center hole. The bearing is there just to center the gear perfectly on the ring gear. An 8X12 bushing would work also but I couldn’t find one.
I take the Traxxas output gear with the posts and bearing and I slip it on the ring gear, I rotate it to center the posts between the screw holes of the ring gear the best I can and with a 2.3 mm drill bit chucked in the drill press, I go through the posts and make contact with the ring gear. The 2.3 mm bit will not touch or damage the threads in the posts, this is just to make a couple marks on the ring gear to show me exactly where to drill the 3 mm holes with the carbide bit. I take off the Traxxas output gear and then I can make the holes and counter sink them.



Then I take a 6 mm threaded rod I have and with two nuts and two washers, I secure the ring gear to the threaded rod. I can then chuck the rod in my drill press and with an angle grinder, I grind off the teeth until the gear is left with a half millimeter lip that will fit over the diff case.



This step is optional; I chuck the threaded rod in a power drill and with a belt sander, I can clean up the marks left by the grinder.

Here’s the finished ring gear from both sides, now transformed into a cap. You can see the counter sink holes on the inside of the cap.



We’re ready to assemble the center diff. I start with securing the posts on the ring gear with the M3X6 mm flathead screws. I put blue Locktite on the threads.

[mistercrash]

Then I put the 8X12X3.5 bearing on the cap. Here you can see a shim underneath the bearing, you can do without it. I had the shim so I used it, it just positions the bearing in the middle of the output gear.



I assemble the diff with my choice of diff lube. I like to run 100k for a stiff diff. On 4S, this lube is thick enough to allow some wheelies but unloading to the front is minimal. 50k will give you a looser diff with more unloading to the front but on 4S wheelies are practically inexistent.



I slip on the Traxxas output gear over the posts and bearing.



Now for the carbon fiber disk to hold the gear in place with two M3X6 mm flathead screws.



The last part is one of the plastic spacers that come with the stock output gear and shaft of the ERBE. I sanded it down to the right length and it serves as a spacer so the CD can butt against the bearing in the tranny case.



I slipped it on the output shaft and in the carbon fiber disk until it is well seated against the cap and put a drop of CA glue to glue it to the carbon fiber disk.



Now install the CD in your ERBE and enjoy some trouble free CD action for racing. Next posts will be the Traxxas TRA3985X output gear installed on the scjrss and CowboyRay CDs.

[Chadworkz]

As always, MC, you have done something nothing short of amazing!

[revo guy]

Awsome, Just Awsome. Any chance of you selling these?

And if not how would you perfectly center the hole in the output shaft?

[mistercrash]

Originally Posted by revo guy

how would you perfectly center the hole in the output shaft?

I made a simple jig from a piece of 1/2'' X 1'' X 2'' steel. The jig has to be made very precisely, if you can make it with good precision then it will help you have perfectly centered holes in your shafts every time. I just put the output shaft in it, flush with the surface, tighten the set screw so the shaft doesn't move, I put the jig in a drill press vise much like this one and drill in the hole of the jig which guides the drill bit.

[mistercrash]

I FOUND IT!!!!
Here's where I got the idea, it was ''its-me'' that came up with the idea of the posts. I was sure he used 4 but apparently he used two. So finally, thank you its-me for the brilliant idea.

Here's the post
http://monster.traxxas.com/showpost....&postcount=336

[mistercrash]

So here's how I installed the Traxxas output gear on the Hyper 7 CD that scjrss made. Here's the cap made from the Hyper 7 spur gear with the 4 holes that are threaded with M3 threads.



The red you see in the holes is just something I am trying to stop lube seapage between the threads and the screws. It's very sticky and tough tape used to tape the seams when you put vapor barrier on your house's walls.



Here's the CD assembled ready for the output gear.



Other than the center hole that was trimmed to let the 8X12X3.5 bearing go deeper in the gear, it didn't need any more modifications. The thick spokes of the output gear are lined up between the threaded holes of the cap.



Four M3X16 mm flathead screws that were trimmed down to 14.5 mm in length to secure the output gear to the CD.



And here is the final product ready to use.

[mistercrash]

Finally here's how I put the Traxxas output gear on the CowboyRay CD. Here's three shots of the machined diff cap. This is a well used cap so that's why it looks a little grungy.



A shot of the stock Traxxas output gear on the left and the modified one on the right. Some grinding was needed in the spokes for the screws to meet the holes in the cap and some grinding of the spokes from underneath the gear so it would fit on the cap's elevated portion.



Here's the CD assembled.



And here is the output gear on the cap lining up with the cap's holes for the screws.



The finish CowboyRay CD with the Traxxas output gear using 4 M3X8 mm flathead screws to secure it to the diff cap.

[sjcrss]

Very nice MC, I like the new design.....great job

[Chadworkz]

Sick, just sick!

[revo guy]

MC could SAE drill bits of similar size also be used? If not any places in Canada (winnipeg, mb) that I might find a 2.6mm, 3mm and the countersink locally? If not does that site you linked have a 2.6mm bit?

[mistercrash]

The site I linked has a 2.5 mm straight flute carbide bit but not a 2.6. This site has a 2.6 mm Tungsten carbide bit, but it says it's a drill bit and not a straight flute bit. It will do the job but a drill bit is more fragile than a straight flute so you have to be careful and go slow, especially when the tip of the bit is just about to go through the piece you're drilling. I made 3mm holes for 3 mm screws but a 1/8'' bit would do the same job as it is 3.175 mm. Close enough IMHO. I don't know of any places in Winnipeg to find carbide tools.

[revo guy]

So then for the 2.6mm would a 7/64 (2.78mm) work for the output shaft?

[mistercrash]

Originally Posted by revo guy

So then for the 2.6mm would a 7/64 (2.78mm) work for the output shaft?

The real measurement of the hole for the spider gear pin in the shaft is 2.5 mm. I went with 2.6 because it gives me a little more play just in case the hole I made is off by a thousandth or two. If you have a way of making an absolute centered hole in the shaft you can use a 2.5 mm bit. If you're like me and your work is ''precise enough'' then I suggest a 2.6 mm. 7/64th or 2.78 mm is too big IMO, the pin will wobble in the shaft too much.

[mistercrash]

It took me more than 4 hours total but I finally did it. My ERBE is now running with 5.5 mm bullet connectors.

ESC bullets


Ready to go with a couple 2S packs plugged in


The parallel harness


Now I don't know what to do next on this ERBE. I think I covered just about everything and addressed a lot of issues. The thing is running so well now when I race or bash it. I'm out of ideas, I need to get a new RC. How about a Losi 8ight E 2.0 buggy.