Center diff as a slipper?

[BrianG]

I recently replaced the chassis on my Hyper8 (bent getting too overzealous when jumping), but didn't realize the Hyper8.5 chassis is 4mm longer than the older 8. I thought the extensions were an optional part, but turns out you can get 2mm in F and R, 4mm in F, or 4mm in rear - but always a total of 4mm longer.

Anyhoo, my dogbones are too short, but I found one in my parts bin that was perfect for the rear. So, I put that on and ran around a bit in RWD only (front bone totally out). Obviously, the CD limited my take-off, but then got to thinking; what if I use really thick fluid? So, I grabbed an extra CD, changed the fluid to 100k, and then ran that abit. Despite still being 2WD, it handled surprisingly well. The thick fluid allowed plenty of punch, yet really helped tame the take-offs. 100k is a tad too loose for my taste, but I think 200k would be perfect.

Anyway, just an observation. I may just run like this for a while.

[hootie7159]

this could be yet ANOTHER class in racing.... 2WD buggy OR 2WD 1/8th scale corr racing....time to separate the real drivers from the novice ones....driving 2wd was always harder than 4wd :) .....you might be on to something brian...

[MetalMan]

I can imagine it turns extremely well too! Only problem is that the weight isn't optimized for RWD, but oh well.

[BrianG]

Originally Posted by MetalMan

I can imagine it turns extremely well too! Only problem is that the weight isn't optimized for RWD, but oh well.

No, it's not optimized for RWD, but it did work quite well. Optimization would be a matter of pushing the motor and batt tray a little further back.


It was just an idea for a slipper system that is less prone to wear than a pad-based system. Sure, something has to absorb the extra power during slip, but fluid should be able to dissipate that far better I would think. Just thinking a little out of the box...

The diff will more than likely overheat and commit suicide by the end of a 15 minute race.

[MetalMan]

With a plastic diff cup that is quite likely - how about with an aluminum case? I used to have the Savage aluminum diff cup on a center diff in one of my heavier vehicles, and I can recall it being quite hot to the touch. But that vehicle was maybe 5lbs. heavier than Brian's buggy and had more power, along with MT tires.

[BrianG]

I can see heat being an issue if it diff'd out a lot, which would be caused by oil that was too loose. But the thicker oil necessary for this application would limit the diff action to only take-offs and maybe on-power landings. But yes, an aluminum case would probably be recommended, but then again, I ran for about 10 minutes with the stock plastic case and it was only warm to the touch. Again probably only because the fluid was thick limiting the diff action.

The idea is to have the diff basically locked unless too much power is applied.

Personally, I think it's a neat idea and might build a cheap buggy based on this. Getting rid of the front driveshaft, axles, diff, etc would lighten the load quite a bit. Not to mention allowing different layout schemes since the front will be more open. Might just be my next "Project X" entry...

[lincpimp]

Originally Posted by Cowboy

The diff will more than likely overheat and commit suicide by the end of a 15 minute race.

Put a fan over it for forced cooling HAHAHAHA

I had to say it, sorry Brian!

[BrianG]

Originally Posted by lincpimp

Put a fan over it for forced cooling HAHAHAHA

I had to say it, sorry Brian!

[lincpimp]

When I first started the direct to diff stuff I was going to use some sort of viscous coupling between the outrunner and the driveshaft. Similar to what you are doing now, I wias going to drive into one outdrive of the diff, and output to the rear diff from the other outdrive. If the fluid was thick enough the entire diff would turn, but if sufficient load was placed on the wheels just the input and the case would rotate. I eventually scrapped the idea due to weight concerns, as I would have to run 2 setups for 4wd.