Savage BL Conversion

[spiftacu1ar]

Thanks. I have updated my CAD to accept a max bearing to bearing (outside) dimension of 34.3mm. The total mass now is about 218.6grams with room to reduce mass if neccesary.

Anybody know how far the slipper adjustment hole is from either of the bearings. I would like to add an opening to adjust the slipper without taking apart the truck. (kind of like the shift adjustment on the stock savage)

[spiftacu1ar]

Changed my minf. I made the outside dimension 32.6, I don't think I will be using the hyper8 diff if there are other diffs that do the same thing in a smaller size. Unless, of course, there is a reason that the hyper8 diff is somehow superior. Is it?

[spiftacu1ar]

UPDATE:
Now that school is out, I have more time to work on this project (at least for a couple weeks until my internship begins).

So, getting these made via CNC mill from aluminum will be VERY expensive. But who cares if its made from aluminum. I mean, its a tranny, and as far as the chassis is concerned, it does little to strengthen the vehicle. (which is why no one really uses the few avaible alum trannies for the savage)

I have access to a rapid prototyping machine that is much more practical.

I will be churning out one two for myself this coming week. I am wondering if anybody would be interested in a plastic version. A few changes may be made to the design you see now, but overall, it will be the same. Instead of tapping the holes, i will make holes ready to be tapped, but since its plastic, I will let the screw thread itself in. Machine screws will work fine, plastic screws are not neccesary. (I have always found the machine screws to be more snug than actual plastic screws anyways.)

Also, since rapid protoype makes it easier to do curves (like things curved in multiple dimensions), I may add some extra stuff (or remove) to make assembly easier. I can also easily customize them for different motors/pinion sizes if needed.

For low kv motors, I may offer a version that sits the motor a tad higher (like .125" or .25") to allow larger pinions (15+ teeth)

[lincpimp]

Sounds good to me, I would be interested in one to try in my 5th scale savage. Pm me a price...

[spiftacu1ar]

Also, to anyone interested, please understand these 2 things:
1) You will need to get ahold of your own custom length dogbones (as the output shaft is offcenter, and the gearbox is narrower than stock).
2) It is HIGHLY reccomendded that one use a skid plate under this. WHY? I designed this for my FLM tvp with skid plate, and I made the bottom pretty thin near where the spur goes in order to keep CG low as possible. (I may or may not make a version with a thick bottom for people not using skid plates)

UPDATE:
cahnged the parameters in the CAD to reflect the change in material. The new mass of the gearbox itself is approximately 102grams not including hardware (screws, etc). This mass also includes the included ESC deck.

[spiftacu1ar]

UPDATED PICS ADDED: HEre is a newer version of the gearbox including fillets since it will be made from plastic. THe deck you see on top is for mounting a CC Mamba MOnster. It has slots for zip ties built in. The deck is removable, and other versions for larger ESC's can be made.





Based on FLM tvp's, so the motor/ esc deck will end up where the stock reciever box goes. If you want to keep the recieevr box, you can drill new mountin holes and mount it the other way (so the motor is at the rear).

[RC-Monster Mike]

Cool looking tranny. I understand that some people want the gearbox enclosed, but there really is no need to do it - and any lube you think you may put on the gears will fly off regardless of if there is an enclosure or not. One huge advantage of an open gearbox when using the slipperential is the ability to adjust the slipper without taking it all apart to get to the adjustment nut. Another possible advantage I can think of is the occasional situation where the pinion set screw loosens. It can loosen to the point of actually coming out of the pinion - in an open design, it just flies away. In the closed box, it is likely to get into the gear mesh and cause carnage.
Also, I think the prototype will be fine with the rapid prototyping, but the motor has some weight, and there will be a substantial amount of torque on the assembly as the motor generates the needed power - aluminum is probably the best bet for a rigid tranny and sound gear mesh. Looks to be a cool project and I am excited to see it completed. :)

[spiftacu1ar]

Originally Posted by RC-Monster Mike

Cool looking tranny. I understand that some people want the gearbox enclosed, but there really is no need to do it - and any lube you think you may put on the gears will fly off regardless of if there is an enclosure or not. One huge advantage of an open gearbox when using the slipperential is the ability to adjust the slipper without taking it all apart to get to the adjustment nut. Another possible advantage I can think of is the occasional situation where the pinion set screw loosens. It can loosen to the point of actually coming out of the pinion - in an open design, it just flies away. In the closed box, it is likely to get into the gear mesh and cause carnage.
Also, I think the prototype will be fine with the rapid prototyping, but the motor has some weight, and there will be a substantial amount of torque on the assembly as the motor generates the needed power - aluminum is probably the best bet for a rigid tranny and sound gear mesh. Looks to be a cool project and I am excited to see it completed. :)

About the pinion getting loose, generally, the set screw gets loose enought that the pinion doesn't spin with the motor, and then still has to back out quite a few turns before coming loose. I don't see how it would go flying out. ALso, I was going to have holes on the final version for adjustments.

Secondly, I called the shop today, and found out they charge $50 per cubic inch printed, so its much too expensive. Im getting quotes for cnc milling 6061-t6 alum from some other places.

You guys have a lot of custom made stuff, but i wasn't sure if you did machining in house. If you do, let me know, maybe I can get a quote?

EDIT: Also about the lube flying off. I made the circle around the spur only 1 mm from the spur itself, so once could put a bunch of low viscosity lubricant at the bottom , so even if it flies off, it will pick more up at the bottom. Kinda lke the oil pan in a car. I kept assembly in mind as well, so you can add oil without dissassembling it. ALso, if you look at the other thread, you will notice there is a removable cover over the pinion for setting the mesh easily.

I don't like open for bashing because if you are jsut drifting around in dirt i think soem of the rock could damage the gears. I konw there is dirt on the gears on my kershaw gearbox, and even if it doens't shred immediately, it definately wears the gears.

[RC-Monster Mike]

If you have a healthy flat spot on the motor shaft(like Castle or neu), the pinion can be quite loose and the motor will still enagage. It can happen and has - just thought I would make mention of it.
All our items start production in house until volume justifies sending it out(or my time). Yes, I could make it, but not very fast, as I am up to my neck in projects at the moment.
Regarding the oil/lube flying off - I would run dry myself, but a sticky lubricant in very small quantitiy would be the most I would suggest. You wouldn't want the main power transmission to have to trudge through any oil at all - it would rob tons of power and generate a lot of motor, esc and battery heat (would have the same affect as oil in the sealed front/rear diff in that it would SLOW DOWN movement). If using the Slipperential, it would serve to defeat the slipper(make it too slippery) anyways, but even a straight diff shouldn't run through liquid on the power side. :)

[spiftacu1ar]

Well, I wasn't planning to run oil, but my point was if someone wanted to, they could. Also, i meant a very little amount of low weight oil. Like only enough so the tips of the gear teeth would touch it. no so much that it is submerged.
My main reason for runninng sealed is the dirt. also, it makes mounting easier, since you have more surface to moun to. i.e., i can make it a drop in repalcement. Most center diffs i have seen are mounted to a skid palte, sicne that allows you to drill holes wherever you want.

Also, the pinion can be quite loose and still engage, you are right. But if the set back out to the point where it cannot possible touch the shaft, the set screw is still inside the pinion itself. And would have to back out at least 2 or 3 more turns before it could fall out.
I understand it could happen on rare occasions, but I do not see that happening often enough for it be an issue. The easiest way to explain would be for you to pick up a pinion
and then loosen the set screw until you can no lonher see it through the hole the sahft goes through. (that is how much it would have to back out before it stops engaging, flat or not). Now see how many turns you have to go before it comes out. I jsut dont see that coming out of a stationary pinion.

[spiftacu1ar]

Oh, I forgot to ask, how long is the backlog if you make it. Cna you give me a quote, I can send you the necceasry files (although they are not finished yet, just for quote purposes)

[RC-Monster Mike]

Any oil bath at all would be a bad idea IMO. Even if it just skims the teeth, it would provide resistance. Also, unless the case is sealed with o-rings, dirt will get into it - oil attracts dirt, so you would effectively have a power robbing gear box that grinds itself to death with this strategy - like a sand blaster. :)
I agree, it is rare to have the set screw fly completely off - which is why I said "occasional" in the initial statement. No explanation needed. It can and has happened - to me even. Not often, but possible. I will also say that I have lost my pinion set screw more often than I have foiled the gears due to the open case/no case. :)

I am reluctant to attempt to quote a date at this point - in addition to a few custom projects for customers, I have my own backlog of "new stuff" that I am trying to work on. I will gladly take look and try to determine a realistic price if you like, though. :)

[Savage03]

This still a go? Debating on the kershaw for my savage conversion but from the reading this would be much better since well the savage slipper blows.
Saw the other thread and he got it mounted but not sure if he made the slipper/motor mount....Mike maybe have plans on making a setup for the savage?

[spiftacu1ar]

I couldn't find a place to do it at a reasonable price. FLM price might not be too bad, custom machining is generally 150% of a similar item they have. HOwever, they take FOREVER to reply to emails, and I gave up on them. I working on another design right now that can be made on a 3-axis, non CNC mill thuogh. I can go to the techshop and crank it out by hand. It's not a closed design though, it will be open. It may also rely on a skid plate (which I was trying to avoid). I will let you know when the design is finished. I'm trying to find a way for it to mount up to the chassis sirectly, not the skid-plate. I hate when removing the skid plate means components come out.

EDIT: If mike releases his own setup, that would be ideal, becasue ti would proabably be cheaper anyways, Plus he has his own CNC mills, so he can do a lot more. If he does it, I would snatch one up soon.

SPeaking of which, when I made the last update, Mike had said he could quote me on my project, but it would take a long time, b/c he was backlogged on production. I *might* give up my designs (for the sealed one on these pages) and see if he wants to make/sell them.

[Dafni]

Originally Posted by spiftacu1ar

I hate when removing the skid plate means components come out.

Well, you better stay away from 1/8 truggies n buggies then

Just playing mate, couldn't resist that one.

Honestly, on Savage center-diff conversions, I found that when you can take the skid plate off with the diff/motor/ESC/etc it makes for a very user friendly layout. Things like adjusting a slipperdiff, even just changing gearing become much easier.
Especially when you want the batteries inside the TVPs a Savage can become a pretty tightly crowded affair, making even the simplest jobs a PITA. So easy acces to everything by just taking out the skid-unit is nice IMO.

Just thought I share my experience with these kind of conversions.

Daf