YACDM (yet another center diff mod)

Hey guys,
Took me a while, but looks like I have finished creating my center diff mod for my Savage.
I am running Xerun 2000kv motor in it now, but I am planning to change it to one of those big leopard 5682 motors (1000 or 1360kv). Not only they are big and torquey, but also will be easier to gear properly. 2000kv motor on 4s gives me theoretical speed of 50mph or so...
Some details of changes done:
- center diff comes from Losi 8ight-t, mount is custom made of 8mm thick alu
- front dogbone is from Alza-Racing (thankfully Dejan had one conversion set with just the length I needed)
- radio box is waterproof from Traxxas (Stampede I think?)
- lipos are mounted between TVPs. Still have to be 2 lipos, as the front dogbone is running in the center between them
- rollcage made of 12mm nylon rods. They are super cheap - which is why I made it in the first place. Got tired of wasting $$$ on bodies.
- Baja knobby wheels are on the way...

Didn't have a real chance to test it yet. If I do like it, I will probably make new TVPs, as those come from old XL and they are full of holes because I used them for various prototypes ;)

Just a couple of pics now, will post more later if you are interested Wink

:

Looks really amazing Twisted Evil

If I may suggest something, you are going to need more chassis bracing for sure. Removing the tranny also removes ALOT of bracing. I added more and now the truck is a tank

Also where do the batteries go?

Thanks!
Yeah, I admit that I am a bit worried about bracing - will have to figure something out once I get new TVPs made for this conversion. This one is so full of holes that it wouldn't last long anyway ;)

Here is where lipos are mounted, without zip-ties that usually keep them in place. Between them is the seriously beefy Alza-racing dogbone (it's twice the thickness of original XL HD dogbone Twisted Evil

)

Radio box next to servo and the diff mount:

Hows the movement of the lipos. I ask because of the dogbone going between them and in the pic you can see how close they are to the diff cup...spinning like made at speed looks like it could chew something up. I can see your foam blocks in there to try to account for this...

Do you notice any flex with that cut tvp? I chopped mine way more than that and didn't have any issues, but I never did any super extreme jumps with it for fear it would buckle.

Yeah, I placed the small pieces of foam to prevent lipos getting shredded by spinning differential cup. Once I secure them with zipties they are practically immovable.
Chassis flex is minimal, I am just worried about one place on right TVP where old motor mount used to be - it's missing around 1/3 of material there.
Once I return from my holidays I will drive it hard and see what happens Twisted Evil

I just returned from a bashing session... and WOW! That thing is absolutely fantastic!
It handles so much better than a regular Flux. Body roll is no longer an issue, with lipos between TVPs and also lower than normally. I ran stock GT2s with stock springs and had to try real hard to flip the truck on corners.
Rollcage also rocks! Didn't do any serious jumps, but did try to "test" it as hard as I could (which involved 50ft cartwheels at top speed Laughing

) Looks like it flexes enough to absorb impacts. The horn on the front absorbs a lot of energy as it flexes at least 2 inches on impact.

Two things I am worried about:
- I wonder how long will the spider gears in diff last... will have to open center diff and see if there is any sign of wear
- gearing is way too high... even on 4s and 13t pinion the truck was way too fast. And I am planning to put Baja wheels on it this weekend... I guess I have to try some ridiculously small pinion (8-9t) or buy a lower KV motor. I saw new Leopard 4092 1050kv motors, specs look very nice Smile

RCmonster makes some killer pinions and they go as low as a 9t pinion. My current setup is 12/46 on 6s with GT2s

Im super stoked to hear you like the CD, I think its the best mod for a flux

12/46 with stock 2200kv motor on 6s?? Wow, did you measure the speed?

Haha no I havent put the truck on GPS yet. Using the GT2s at 3/4 throttle is nutso it will just flip LOL

My guess is right now the truck does about 45mph, its not faster than my nitro for sure.

But in time ill tag it on radar or GPS or both haha

Well SpeedCalc at Scriptasylum says that at 12/46 & 6s your truck has a theoretical top speed of nearly 85mph Shocked

That's not taking into account drag, powertrain losses etc. but still very high... Should be able to reach 60mph easy Wink

You might be right but ill have to tag it to be sure. I know this tho im going to need to belted wheels to try top speed runs. I do have a set, ill tell you this tho it will fly but I dont think its as fast as my nitro savage

Got some new wheels today... Straight from Hong Kong :D

Even though they only cost $30 a pair, they really look and feel good... Rubber is nice and medium-hard compound. Those are beadlock rims and hex in them is metal so they should never strip.
As soon as I receive the hexes (probably Monday) I will test them out in the field.

Quick shot with new wheels on. Integy hexes arrived, and I can't say I am too impressed... They're... "Integy quality" if you know what I mean.

Sorry about the mess in the background Wink

huge heavy wheels with such a tall gearing???

Only because it's the smallest pinion I have at the moment... Still pondering whether to buy a new motor with lower kv or get some really small pinions...

i say get the 1717, should kick some asses out there...

Here's the link goths pinions from rcmonster. I highly suggest dropping down a few teeth on the pinion with those wheels

http://rc-monster.com/proddetail.php?prod=5mmmod1pinion

your diff mount has a lot of space on sides so you could try some bigger spur gear. 52t or 54. 12/52 should be 75mph and 12/54 should be 72. A bigger spur would also give you more gearing options for other pinions

I have 50t spur which is biggest I could find for Losi diff. I think it is easier to drop from 13t to 12t pinion - which is about equivalent to increasing 50t to 54t on spur gear.
If I change motor I will be able to use bigger pinions which I have a couple of. Plus, it's more powerful than Xerun:
http://www.leopardhobby.com/product/product_veiws.asp?id=1500&functionID=01020201
I am thinking 1300 or 1390kv motor


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