New Savage Center Diff ideas......
 

Well I tore the truck down and sold the Kershaw tranny and 1717 motor. I picked up a 1520 and HB D8T center diff instead.

I have 3 different concepts in my head that I want to try. I'm close to finishing the first one in Solidworks so I thought I would post some pics. I just need to add the shelf for the RX and ESC. Possibly do some weight reduction.
- What I don't like about this idea is the center of gravity is very high.
- What I do like is the center diff drops out the bottom while the motor and housing stays in place.

Pics attached.

More pics.

Very cool design, alot nicer than my settup. I take it you'll be using a skid plate of some kind. alot of spur exposed on the bottom

I can drop the center diff out the bottom of my truck and it is a big plus. If you move the motor to the side you will able to get it a lot lower and fit something beside it to help counter balance. My motor still sits a bit across the center line.

Check my build here for ideas
http://www.rc-monster.com/forum/showthread.php?t=26870

http://i1010.photobucket.com/albums/...t/IMG_0415.jpg

Ya the spur gear does hang lower than I like. It was either that or the motor sits higher. I intentionally designed it using a 50T spur gear so I can always use a smaller one. Plan B was to take one of my RPM skids and see if I can heat it up and form it around the spur. (Or just cut a slot and deal with it)

The second concept is going to move the spur gear higher and hang out the side of the chassis so the motor sits lower and off to the side like _DV's layout.

Nice build _dV. I just went through the whole thing. Very clean and solid. I like how you can fit 4s and 6s inside of the tvp's. The slipperential looks a lot smaller than I thought it was.

I was originally concerned about having a cutout in the skid plate for the spur. After countless runs on various terrain though I can safely say it's not a problem. I haven't had a single issue with small rocks being jammed or the spur being damaged(metal spur). I do have a large cutout though due to the slipper being a larger diameter than a normal diff.

One thing that I did notice though is that your diff is an enclosed area. If small rocks get in there the only way they could get out would be through the cutout in the bottom, or if the truck turns upside down.

That's a good point^^

I may open that bottom plate up so the diff isn't tightly enclosed.

would be cool if someone sold this kind of diff conversion (please correct me if im wrong:whistle:)

I think RCM has a universal diff mount that can be integrated. Once I settle on a design I like, I plan on making 5 or 10 of them. It tends to be cheaper that way when you have them machined.

i would be interested for sure. interested to see what you come up with. kinda like the current design though

I would be interested in one as well. You have some very good ideas, this would really make this truck alot better.

I'll talk with the moderators on here to make sure I don't step on any toes with selling some extras.

I'm not an approved vendor.

Some updated pics:

1. Opened pocket around diff per _dV's suggestions.
2. Slotted hole for motor shaft and reduce diameter to keep dirt out.
3. Added shelf for electronics.
4. Chamfered some sharp edges.
5. Added slots on 2 sides for motor wire routing to ESC.

One more pic

Looking good! hopefully Mr. Mike allows a few extras to be exchanged

are you making up custom dogbone(s) too?

This setup uses the aftermarket flux center driveshafts.

http://www3.towerhobbies.com/cgi-bin...2&I=LXGPE9&P=K

http://www3.towerhobbies.com/cgi-bin...?&I=LXGPE8&P=M

I haven't ordered them yet or I would have drawn them in there.

hey those are the same as a stock replacement so dont you still need longer ones? hpi measures pin to pin and those are measured pin to cup pin so they arent actually any longer than stock flux. i though they were also and ordered one a while ago to try on a flat chassis project i wanted to make, but it was the same as the 78 with the stock drive cup.
your chassis pics look good. must be a low kv motor you have

i just figured out you maybe made the chassis plates shorter to make up for the more small center diff. is that right?

Im using 2 of the rear drive shafts. When I started the project I centered the diff between the front and the rear and then measured the distance. I determined that 93mm was my sweet spot so I searched online for all available dog bones and universals of that size. It turned out the HPI drive shafts worked.

They arrived last night so I need to model them in solidworks and see how they fit.

The motor is a 1600kv

Well you were right^^

The axles are too short. Back to the drawing board. I guess I will either eat the $40.00 and find some new dogbones or eat the $50 chassis and make a shorter one.

I finally have a few minutes to mess with the project. I decided to pull the CVD's out of my LST2 and what do you know.... They fit!! Well close anyway. The are just a hair too long and bind if they are straight. If I raise the center diff they seem to work nice.

I modeled them up tonight without moving the center diff yet. Here are some pics.

Hey bud, whats the length of the CVD? pin to pin..

I need 93mm. (3.66 in)

The Losi cvd's are 3.835 in.

After working on this last night I don't like it. The diff needs to move way up. I'll look for another dogbone or change things around.

Is this the front or the rear? Do you have the other measurement as well?

That was for both. I have the diff centered in the chassis.

No what I meant was the measurement for front or rear of LST2 CVD.. Or do they have same CVD for front and rear?

Is this set up for stock length or xl?

The LST2 shafts are the same length for the front and rear. It would have been sweet if they fit.

This is going to be a standard length build.

Design #2 is under way. I've flipped the motor 180 deg so it's now in the front of the truck. I think that will be better for weight distribution. I'm also working on a new bracket layout. The heavy duty Flux CVD will be in the rear and a 110mm dogbone will be in the front.

It's been a while since I updated this post so I thought I would share my progress.

I'm working on the second concept now that is a lot stronger and probably over-kill but that's what makes it fun. My Kershaw tranny would constantly bend hardware from the weight of the motor & tranny.

I changed the hardware from 4-40 to 6-32 screws and all parts are machined from 1/4" 6061-T6 stock. It won't be light but hopefully less than my last 14.8pound Flux. The motor mount changed from vertical slots to a pivot. Easier to mesh and less chance of slipping.

Did I mention the motor also flipped 180 deg and is now in the front of the truck above the servo? The shorter universal will be in the rear where most of the torque is applied. More weight balance to help with traction as well.

More pics......

Also an alternate motor plate with heat sink fins. I'm worried about strentgh though. To get as much surface area as I can the actual meat left to hold the motor is only .100" thick.

With heat sink plate.

I'm really liking the project, myself am still in the middle of something similar.
If you don't like wheelies and want more planted stance, definitely go with motor in front flipped backwards, thats what i did, and it drives really great! still need to update a video in my build.
What esc are you planning on using?
If you are going for mechanical brakes, the motor heatsink you modeled can be thicker to clear the brakes, then you won't be worrying about strength.
planning on machining it yourself or getting it done in a machine / cnc shop?

Thanks man. I'm not planning on using mechanical brakes. My last Savage build had a problem with the brakes being too strong on the 1717. If I tapped the brakes the truck would do a violent front flip. I had to program it out on the MMM. I will use the same ESC again with the 1520.

I plan on machining some it it myself and farming the rest out. I have a bridgeport at work but I'm not the greatest.

I hope with this design, and some programming, I can get on it and the truck just takes off. Before, anything over 1/2 throttle and I was on my lid.

Regarding the dogbone issue. Why not make a custom lentgh cup at the front or rear diff? Obviously you have to have it manufactured properly to avoid unbalance and vibration... but it would give you alot of freedom when playing wit h3D drawings. You can then fiddle with standard dogbone lengths and place motor/batteries as you like.

In my truck I put the batteries far up front and low. like a G-max. works well in regards to the "no wheelies plx" :)

http://www.hpibajaforum.com/forum/sh...4&postcount=96
http://img.tapatalk.com/186ad8e2-1818-d3b2.jpg

So what all is needed for the 5sc center diff? Will it bolt right in? Anyone done it?