Official Erevo 1/8 scale center diff thread - Page 3 - RC-Monster Forums

simplechamp · 09.11.2009, 09:19 PM

SUCCESS!

I annealed the metal, made a divot with some diamond dremel bits, and then drilled with carbide bit and tapped with cobalt tap. Couldn't believe how easy the drill and tap went through. I almost wonder if I softened too much or if the bits just made it that easy? I wasn't that surprised at the carbide bit chewing through the steel, but the tap was also much easier than I expected, barely required any force. The threads seem solid though and the drill bit was 2.5mm.

I feel kind of dumb now. I had this turned into such a big deal in my head and it turned out to be no problem. Oh well, it's done now! Going to do a test fit and see if anything else needs to be changed. Thanks again for all the help guys!

sjcrss · 09.11.2009, 09:44 PM

Looks good, great job, I would make sure the heads of the bolts don't interfere with anything inside, I don't think they will, i can't remember off of the top of my head right now...sorry, but great work ..

simplechamp · 09.11.2009, 10:15 PM

Test fit confirms everything is A-OK including the shortened outputs. The screws are very close to the inside of the trans case, but a few shims on that end gave them enough clearance. Rotation is smooth all the way around with no binding. All there's left to do is fill it up with silicone oil and make sure everything seals up tight.

mistercrash · 09.11.2009, 10:51 PM

I'm so glad it's finally done

Just joking SC

If everything checks out, if it rolls nice and free inside the tranny and there's no big leaks then go out and enjoy it, you'll love it for sure. Great job.

simplechamp · 11:51 PM

It was definitely a learning experience. Knowing what I know now I could probably put one of these together over a weekend. To anyone thinking about making one of these diffs: if I can do it, anyone can. Don't be intimidated by the hardened steel, it's very do-able with the right tools and right advice.

EDIT: One more question about the silicone oil. 50k and 100k seem very high to me for a 1/8 diff. Is that just the nature of the E-revo to need heavier fluids even with this hybrid diff? Or do you guys just like the diff to be very firm? I figured once I swapped all my diffs to 1/8 diffs I could run similar setup to a truggy (7k/10k/3k for example), but now it seems like I'll need heavier weight oils?

sjcrss · 07:12 AM

Here is a article I typed up out of RC driver some time ago, it should help explain the basic concepts behind diff oils...
http://www.rc-monster.com/forum/showthread.php?t=5050

mistercrash · 10:25 AM

Quote:

Originally Posted by simplechamp

EDIT: One more question about the silicone oil. 50k and 100k seem very high to me for a 1/8 diff. Is that just the nature of the E-revo to need heavier fluids even with this hybrid diff? Or do you guys just like the diff to be very firm? I figured once I swapped all my diffs to 1/8 diffs I could run similar setup to a truggy (7k/10k/3k for example), but now it seems like I'll need heavier weight oils?

Great article there scjrss, I think that the weight of the truck and the amount of suspension travel it has are a big part of the reason why the center diff needs heavier oil than a Truggy would. The E-Revo squats quite a bit in the rear on acceleration, the front end wants to go way up in the air because of the power of the MMM. Anyway, the truck looses a lot of front traction on acceleration because so much of its weight is transferred to the back wheels. With that said, if the CD has thin lube in it, the front wheels will just spin like crazy and overall acceleration will suffer. Weight transfer can be controlled a bit by putting the front pushrods in the most outer hole of the suspension table, less droop. Putting the hinge pin of the rear suspension arms in the lower hole helps two I've heard. Using the extended rear arms for a longer wheel base and puting your batteries to the front of the battery compartments.
With 10k in the CD, your truck will not wheely, but it will feel sluggish on acceleration and the front tires will look like pizza cutters. With 50k, you will be able to wheely moderately on high traction surfaces, less unloading to the front but still a lot if you don't use throttle control. The acceleration will be much better. With 100k, you can wheelie on demand on asphalt and grass, but not on dirt. High wheelies that make the rear wing touch the ground but the truck won't flip on its lid. Throttle control is a must on start ups, accelerations are explosives on asphalt and grass but a little squirrely on dirt (throttle control fixes that)
This is just from what I have tried up to now, I also tried 30k and I thought it unloaded too much to the front, less than the 10k but not by much.
From what I have experienced and according to MY preferences, the ideal weight lube for me would be around 68.24k to 72.86k

Now about those machinists you talked to and wouldn't help you, go back to them and show them what you did.

sjcrss · 09.12.2009, 10:38 AM

Thanks MC, I agree about the machinists, go back and show them what you did......since they said it couldn't be done....as for the diff oil, I like mine at 50k, but I also have throttle, ect and a few other things set on my radio, and this helps me control my erevo, but it still can wheelie on asphalt as well, still kinda tweaking it.....

simplechamp · 09.18.2009, 01:00 PM

Anyone have any new developments?

I still need to get silicone diff fluid, then I'll be dropping in all of the 8th scale diffs. Decided to start at 10k front, 50k center, and 10k rear. Not sure if the F/R diffs will be thick enough? I have the 10k fluid but I need to get 50k. If the 10k is too thin i will need to also order some 30k and run 30k/50k/10k or 30k/50k/30k. What do you guys think?

sjcrss · 09.18.2009, 04:45 PM

I use 30k/50k/30k in mine..it works for me

mistercrash · 09.18.2009, 07:52 PM

The last CDs I will probably make. They are IMO the best built and best looking ones I've done so far. Made from the heavy duty Losi diffs, one for the ERevo tranny and one for the nitro Revo tranny. For the posts, I found that these Kyosho ones worked great. The gears were originaly white but I dyed them black because I thought it looked better. One more thing I found out is the Losi hardened steel seems to be harder than the Ofna steel and much harder than the Thunder Tiger steel. That is just by using the same tools to modify and drill them. I wouldn't dare try to put threads in the Losi hardened steel so maybe the machinists were thinking of really hard steel like that when they refused to do the job for SC.

The ERevo one

The nitro Revo one

simplechamp · 08:54 PM

Wow those look perfect MC!

I thought I would mention that I think spot annealing can really do wonders to soften up the steel. I took a small blow-torch and put the very tip of the blue flame exactly where I was going to drill for 10 min. or so. It got a dull red hot, not too bright. Then let it cool to room temp. The carbide drill bit and cobalt tap went through like it was aluminum being worked on. Unfortunately I haven't drilled/tapped the hardened caps without annealing, so I don't have a reference to compare how much the annealing helped. Just going off of what you guys say about the un-annealed steel I can almost guarantee that the annealing will help.

sjcrss · 09.18.2009, 09:00 PM

WOW, MC, those look great......job well done......and to everyone who has made one...great job as well.....I'm glad everyone was able to make one, and hopefull a few more people will to.....

simplechamp · 09.23.2009, 06:49 PM

Ugh... All I'm waiting on is diff oil and it's taking FOREVER to get here. Then the center diff can be dropped in along with the RCM hybrids. Can't wait to have this project completed!

mistercrash · 09.23.2009, 11:11 PM

After all that effort, time and money invested in this, it's ironic that it's presently all useless without a couple of 3 dollar bottles of diff lube