Direct Drive to Diff E Revo Build

[ilpufxit]

Locked diffs would be a problem for sure. The whole concept of direct drive really gave my little brain a stretching but now that I've thought it through, I'm thinking maybe two outrunners back to back in the same center diff location could use a fully electronic system for optimal everything, ie traction control, stability, ABS, the works. It could be a quantum leap in controllability. Is there a software engineer in the house?

[DrKnow65]

servo mixing could be used to drive the front motor harder when turning as the front wheels spin more rpm in a turn. Assuming a 3 channel remote is used. ch1=steering, ch2= rear esc, ch3= front esc.

[sikeston34m]

I'm finding the limitations of the bearings in the truggy diffs.

With the spiral cut gears of the 4.3:1 ratio, the pinion not only side loads the bearing, but it also pushes or pulls against the bearings.

I've been using steel ball bearings and they aren't holding up to the increased torque levels of my setup.

I could hear the diff Pop occasionally in the rear under hard acceleration. I took the diff back apart, and found alot of slop in the bearing closest to the pinion. I swapped positions with the two bearings, reshimmed to take all the play out and it worked perfect.

Now about 4 runs later, it's doing it again. On 6S, it will do 60mph+ and top out very quickly. With NO slipper, the setup is able to transfer all the torque that the motor will make. Which is alot!

A needle bearing with thrust bearing type qualities would be ideal, but I can't find any in this size. 8x14x4mm.

Is Ceramic Nitride the toughest out there in a ball bearing? like this one:
http://www3.towerhobbies.com/cgi-bin...?&I=LXPVB1&P=7

I've heard they are.

@Lincpimp - You need to consider this on the setup you're looking at. Tough Diffs are a must.

[zeropointbug]

Wow, that is deadly looking! Use that with a speed record! I have mentioned the wheel motor idea a few times on this forum, but yeah it won't really work with these monster trucks. MAYBE, smaller on road cars... but they would need a very high power density to keep the weight down in the wheels, like someone said "unsprung weight" is a killer.

A few companies are doing wheel motor for full scale cars however, with GREAT results, works much better than motor/tranny/driveshafts.


About the diffs Sike.... I think all pinions have thrust on them when loaded, these spiral cut gears may just have more pressure is all. I don't really know what the best bearing are in these sizes? Sorry.

[sikeston34m]

Originally Posted by zeropointbug

Wow, that is deadly looking! Use that with a speed record! I have mentioned the wheel motor idea a few times on this forum, but yeah it won't really work with these monster trucks. MAYBE, smaller on road cars... but they would need a very high power density to keep the weight down in the wheels, like someone said "unsprung weight" is a killer.

A few companies are doing wheel motor for full scale cars however, with GREAT results, works much better than motor/tranny/driveshafts.


About the diffs Sike.... I think all pinions have thrust on them when loaded, these spiral cut gears may just have more pressure is all. I don't really know what the best bearing are in these sizes? Sorry.

What diffs are you running in your 7S1P A123 setup? Ever had problems?

I know that truck really runs!

[zeropointbug]

I recently got a Revo 3.3 (September), and am running 7s1p at the moment, with the emaxx tranny (GM single speed). I am using the stock diffs right now, as the truck is quite light (just over 10lbs) the diffs are holding up fine.

7s1p has pretty good power... 7s2p however, halls ass man!

[lincpimp]

Originally Posted by sikeston34m

@Lincpimp - You need to consider this on the setup you're looking at. Tough Diffs are a must.

Yes, I understand the need for a good diff! I have a feeling that your combo of larger (heavier) wheel/tire and higher (numerically) diff ratio put more strain on the pinion gear than my smaller (lighter) wheel/tire and lower (numerically) diff ratio. Your truggy pinion has fewer teeth than my buggy pinion (10 to 13) and that can cause mesh problems as well (not sure if it is?). Plus I will run on road which should offer less traction as my tires have much less contact patch than a mt tire.

The ceramic bearings are most likely a good idea, as they are built better and should last longer.

[Mod Man]

You may want to reconsider running only 1P in that case. If you are getting significantly more power on 2P, then you are overdriving your 1P pack. You will always get a touch more power on 2P because of less voltage drop. However, if there is a huge difference, stick with the 2P. That will keep your 1P packs from prematurely dying.

Matt

[zeropointbug]

Believe me, I have been running A123 packs since spring '06, I have had the most experience with them on this forum... a 7s1p pack can deliver 1300 watts solid, and only gets barely warm to the touch running a 1512/3D. This is probably because the truck is fairly light weight, so not much stress on the pack (plus it handles better with a 1p pack). I too usually recommend 2p packs (mostly with less than 7s though), but the combination of HV, the Neu's efficiency, and light weight truck, 1p is JUST enough to throw the truck around with authority.

As far as cycle life goes, the 1p pack is still delivering a little over 2300mah after >200 cycles at 4C average discharge (15 min runtime) and 4C/10 amp charging.

[Mod Man]

Oh, geeze, sorry. I had no idea you were running A123 cells. I have always run flat lipo cells (mostly Flight Power and Thunder Power Extreme cells). I was assuming these were standard flat cells.

A123s are pretty much bulletproof.

Matt

[its me]

bump??

[Mod Man]

Bump?

Where?

Matt

[sikeston34m]

I had some good success with the custom wound 3530 that I put in the E maxx.

My Ceramic Nitride Bearings came in for the Revo, so I figured I would get this 4130 wound for it and install them all at the same time.

I wound the stator beautifully with 6 strands of 22 awg with 4 turns on each stator pole. I pulled each turn tight as I went and it all laid really well.

After completing the Wye termination, I checked for continuity between the winds and the stator. Dead Short!

I removed the Wye termination thinking maybe it was the last set of winds that was shorted. After testing each leg of the 3 phase winding for continuity to case. I see EACH wind is shorted.

Now I get to start all over. I have decided to dress up this stator some and not pull the wires so hard. I'm gonna take a little more time next round.

When I was pulling it all back off the stator, the shorts are happening at the ends as the wire is being pulled tight.

A little sharp edge removal with a Dremel and several coats of fingernail polish should help. The fingernail polish is non-conductive and will help soften the edge.

Lesson learned. I won't be so rough this time.

[lincpimp]

Originally Posted by sikeston34m

The fingernail polish is non-conductive and will help soften the edge.

Lesson learned. I won't be so rough this time.

What color polish are you using, will you do your nails at the same time?

[sikeston34m]

It's actually Chrome Nail Polish. I hand picked it from this huge bag of little bottles that my daughter's have collected.

Naw, I won't be doing my nails.

I prefer that "Manly" look.