Erevo / Emaxx 1/8 center diff
 

So I have begun designing and constructing a center diff for the erevo / new emaxx tranny. Basing my design around a std 1/8 scale diff cup. So it will employ 4 spider gears and 2 output gears. My current diff cup is a HPI al savage cup that has the steel blocks to reinforce the cross shafts. Strongest design I could find. My adapter will also fit any kyosho, OFNA, or hot bodies cup, and any other cup that has the std 4 hole mount pattern.

Some pics:

http://i206.photobucket.com/albums/b...p/DSCF2514.jpg

http://i206.photobucket.com/albums/b...p/DSCF2515.jpg

http://i206.photobucket.com/albums/b...p/DSCF2516.jpg

The al adapter is not complete yet. It still needs to be cut to the correct length and the end tuned down to accept a 8x12 bearing. The black gear also needs to be milled to a certain thickness, as you can see in the 3rd pic it sits too high compared to the input gear. I have done the measurements and should be able to have the machinist finish the adapter on Monday.

Due to the overall thickness of the diff cup and the adapter, and the diameter of both they will contact the idler gear. My only method of fixing this issue is to remove about 1/5 of the thickness of the teeth from the idler for adequate clearance.

This is necessary due to the mounting issues with the stock lower gear to the adapter. If I can have a gear custom made, I can modify the adapter to place the gear closer to the face of the diff cup, although I may never be able to get it close enough to work without some trimming of the idler. Just not enough room inside the stock tranny case.

More info when I get some more progress! All ideas and thoughts welcome...

Hmmm... Ill be watching this one.

Ok, I see how its looking now....couple of ideas or suggestions possibly....
can you machine adapter to be thinner at the attach point to cup....this can bring the gear closer, also how does the gear attach to it, and the output shafts....I see one side is threaded.....are you going to use a modded stock lower shaft?..all in all...looking good and is a good start....

The lower gear has a .080 think flat area on one end, and I will mount the gear to the adapter thru that. The adapter has to be that thick for the mount screws to have something to screw into. I will use cap head m3x6 screws, just the right length.

I'm watching this one too.

Interesting idea Linc....I might build another E-Revo...

Do you have one of those tmaxx 2.5 Forward only gears? It's thinner than that but I don't have one on hand to make some measurements.

http://www2.gpmd.com/imagel/t/ltrac4991.jpg

http://www3.towerhobbies.com/cgi-bin...?&I=LXCNA8&P=7

I think that is a 26t gear, not 33t...

I may be able to use the gears, modded a bit. If I can get a set, I may try to use them with the next proto shaft. I will probably do this, as I can run one style setup in each of my trucks and see which one breaks first!

http://www3.towerhobbies.com/cgi-bin...?&I=LXTKP2&P=7

One side of the gear is recessed a bit, and only has those 2 ribs where the dog clutch engages. If I mill them out, I can reduce the diameter of most of the al adapter to fit inside of the gear, bringing the gear closer to the diff cup. I would only need a small amount of the adapter to be the full diameter, maybe .050" thick, it is currently .200" thick. I have a truck with a 2 speed setup in it, so I may have to rob the tranny out of it for testing purposes!

Will you have enough space for the screw holes on those emaxx gears? I have a couple of those and was looking at how are you going to mount them.

I am sure that I can figure something out. They look more promising than the stock lower gear.

More progress. Had the machinist turn the output gear down to the correct width, and shorten the adapter and turn it down for the bearing. My measurements were slightly off, but it is going together ok. Need to drill and tap the mounting holes for the output gear and put the diff internals in properly. Then I can do some testing in the erevo with the 1515!!!

http://i206.photobucket.com/albums/b...p/DSCF2519.jpg

http://i206.photobucket.com/albums/b...p/DSCF2518.jpg

http://i206.photobucket.com/albums/b...p/DSCF2517.jpg

wow, that looks awesome linc, let us know how it goes

Thanks guys. I need to order some shims, and have the machinist do a little bit more work, so that I can shim it all properly. Plus I also need some ceramic bearings, as the shielded ones I have may not hold up...

Then the testing begins...

looking go0d...keep us posted on the testing....

Will do!

Are those considered mod1 linc?

The gear pitch is mod 1.

Thanks. That is what I thought. I been looking at ofna centers and I think those are mod 1 as well.

Most if not all 1/8 scale vehicles use mod 1 gearing...

Kinda figured, but had to ask *cough* to sound stupid...... :)

Thats ok, there are no stupid questions, only stupid people! Some a-hole always used to day that to me... You can imagine what I said back!!!

lmao, for sure! Any progress? I know it has only been a day, but getting excited to see the progress of this thing.

I took it back to the machinist to have .050 taken off the bearing area. That way I can use some shims to properly set it up inside the trans case. I will be able to get some mocked up pics today, but have to wait until next week to get all of the parts I need in. I also have to make the output shafts, so I have a fair amount of measuring to do.

I also gave the machinist some diagrams and material to make the adapters to put lst diff cases in a maxx. So I will have a new thread on that soon. Those are much simpler to make, and should provide a good alternative to the other 1/8 scale maxx diff conversions...

Looks great. How much are you paying to get this machining done? I remember Matthew_Armeni paying $88 to get 3 holes drilled!

Honestly, the center diff adapter, gear mods and turning of the stock output shaft has set me back about 200 bucks. And I still have to mount the output gear, and cut/drill the output shaft. Not cheap... That is why I am buying a lathe, so I can prototype these parts myself. I am not sure if I will sell the center diff adapter. I would like a more elegant solution, and for that I need a different lower gear. I have an idea what to use, so I will give that a try...

$88 for three holes is a bit much. My machinist charges $1 a minute ($60 per hour) which is fair, IMO. That is why I am doing the drill/tap for the lower gear mount holes. It really does not matter where they are, so my drill press will do the job just fine.

:oh: That's alot of cash! How much will a lathe set you back? You should consider one of these:
http://www.harborfreight.com/cpi/cta...temnumber=5980

I am liking the look of this one:

http://www.harborfreight.com/cpi/cta...emnumber=45861

Should be a good start, and if I outgrow it I can always sell it locally and buy something bigger.

Nice, but you will *most likely* have to also buy their $150 lathe stand.

I have some really sturdy metal tables, that I can use as a stand.

Linc, im also working on a center diff design as well.......i should have all the parts by this weekend hopefully, and as for some of the lathe work, I'm able to do it at work, at my lunch time......

Shall be interesting to see what you come up with. I have my patent number for mine already, so hopefully you are not infringing on my design...

nope not at all...this is what im doing......
<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8"> <title></title> <meta name="GENERATOR" content="OpenOffice.org 2.4 (Linux)"> <style type="text/css"> <!-- @page { size: 8.5in 11in; margin: 0.79in } P { margin-bottom: 0.08in } --> </style> so here is what i have coming and planning
purchased the following
traxxas cd
ofna hyper 6 spyder diff
acer 8X12 bearings...( these will fit onto end of diff cup and still fit into stock tranny bearing hole, which is 6X12 bearings)
here is the plan....
take apart the traxxas diff, measure it's cup to the hyper diff, use the traxxas outputshafts, with ofna spyders( hopefully they mesh good ) then use the gear off the Traxxas cd... and bolt it to the ofna ring gear, after the teeth are machined off, then drill & tap 4 holes to hold the traxxas lower gear to the modded ring gear... on the front side of the output shaft...I will use a std. 6X12 bearing..... so the back of the diff will be supported in the bearing hole, and the front by the shaft.....that is the intent anyways.......so I hope you don't see this as infringment.....but after seeing yours, i figured there has to be an easier way.....so that anyone can possibly make one with the right parts and some work at the bench at home.....but I'll post pics ect.... as i try to get it all together....

I was just joking. It will be interesting to see how you do with drilling the ofna gear, as it is hardened. Please post some pics when you get some progress.

np...lol, im actually gonna have one of our seasoned machinists at work drill & tap them...he is also runs rc's as well, so he knows about the gear too....i hope the simplier design will work.....not trying to take anything from you.....just seeing if my idea will work......however if it does...I wont produce them (unless people are asking for the modded ring gear....), but more than likely will post info on how to do it yourself.....

My setup is quite involved, not sure if it is worth selling it as it will be expensive. I really need to test it out and see if it will last. I have another idea of how to make it a bit better and simpler. Good luck with your idea, hope it works...

Have you found out if traxxas will sell the output gear seperately like they do with the nitro revo?