Diffrunner concept
 

To bring back my old idea on the integrated-inline-differential-motor package concept (IDM?).

I am not sure who remembers this from the fall, but here is a sketch of what I mean. It would improve efficiency of the powertrain (theoretically), and would allow more space on either side of the chassis for things like batteries, while pushing everything towards the center line of the chassis, thus improving handling characteristics.

Okay, first off I like this idea I am just trying to wrap my brain around it.

It looks in my mind as though due to the shaft running through the motor it would only give you diff action in one direction as the other end of the motor (where the mounting face is in your drawing) would still be controlled directly by the motor shaft.

I guess I am trying to understand how the motor shaft would give you the diff action independently of the motor shaft without a way for the motor to spin the diff like in a center differential setup and allow the two drive shafts some independent movement.

I could very well be missing something.

The Outrunner part of the motor will act like a spur gear and the shaft will run inside the motor to the other side. This is basically bolting the motor to the diff case which seems to benefit outrunner style motors. When will the final unit be built? It looks very easy, but I know there will be challenges with it. I think a new diff case will have to be built for quick access in case things needs to get changed. I also think a larger bearing would be nice to support the outrunner case in place better. Things can twist and bit and jumps will put a high load on it as well.

Maybe I got it all wrong, but it was worth a try :lol:. Awesome idea to exploit the torque available in outrunners.

Makes sense. The motor is tied to the diff cup itself and the shafts run through the motor without being attached to it at all.

Yes, I remember this discussion.

I believe what the picture fails to illustrate is:

The back of the can is attached only to the diff housing. The can is attached to the shaft running through it by a bearing only. No longer a press fit with a set screw.

It would effectively spin the diff housing just like a spur gear spins a center diff.

I believe this design WILL work, but............there's always a but.

Current diff designs do not support this setup. Both in available gear ratios and toughness.

The lowest toughest gear ratio on the market currently is the 13/43 diff setup. I do know MT tires in the 5.75" size won't work with this without cogging. Perhaps a smaller tire size will.

Granted, the diff unloading to the front will cut down on some of the abuse. This then switches the game into trying to not make the diff unload.

This center diff will need the thickest grease you can find, and then some.

One other thing this setup needs, is a good HV ESC with the Mamba Car Software. Come on Castle. LOL

Some thoughts need to be spent on Motor Cooling also. A fan made into the endbell along with an Aluminum motor mount/chassis will help things greatly.

A Really Low KV Motor on 8S to 12S would be hard to beat. :yes:

Yep I remember this! :yipi: Have you made any sort of prototype yet?

I also like the idea of a special inrunner motor of relatively high pole count and low Kv. with a large diameter hollow shaft be used. This would take MUCH technical design as the motors output shaft needs to house the diff output, couple to the diff for power transfer, and somehow support the diff all at the same time. :oh:

Nope not yet, I usually shut down completely from R/C come fall and then get re-inspired in late winter, such as now.

Luc, supporting the outrunner housing is a challenge as well, as there is alot more leverage on it that if you would just use it normally, roughly twice it would seem? Just trying to imagine the forces.

Okay, I see what I was missing. I knew their had to be more to it. I am just tired, and brain is not fully functional.

"Current diff designs do not support this setup. Both in available gear ratios and toughness. But wouldn't this depend on the Kv. of the motor and Volts used? I am sure the ideal unit could be found to match a good racing speed and the correct torque loading to match diffs capacity."

The outrunner shines in the Torque department. Diff design is advancing. I'm impressed with the New E Revo Diffs. I have put my MT through hell and back over the past two years and I'm only on my second set. LOL

I like one members quote. "I don't use a slipper clutch, I use Tires".

We NEED drivetrain parts tough enough to transfer Explosive Torque Levels of power to the wheels. It's getting there. :yes:

"The lowest toughest gear ratio on the market currently is the 13/43 diff setup. I do know MT tires in the 5.75" size won't work with this without cogging. Perhaps a smaller tire size will. This is what I am wondering myself, but haven't you tried this with pretty good success?"

Yes, with a AXI 4130/20 305kv motor. It did work pretty well, but it did cog some on start up. It needs slightly lower gears. Top Speed was lacking. A good Castle HV Controller would take care of this.

Castle has improved startup routines. They may have practically solved this problem themselves. More testing would answer this question OR a lower kv motor and higher voltage.

The Diff will unload to the front wheels. Yep, just like over powered center diffs do now. Be prepared to stiffen things up.

The MMM works fine with outrunners but limits things to 6S operation.

Scorpion answered this problem with their press fit endbell bearing. On the large end of the motor, by the mount.

Three bearings to support the diff/endbell. A large bearing on the mount side, one at the center to the shaft, then the last bearing would support the end of the diff.

Understandable Texas, most people at the track didn't understand it when I drew it out for them either.

Here is the inrunner variant of the concept, obviously more work and design issues. I am still trying to come up with a good connection between hollow output shaft and diff housing. There would have to be some sort of adapter plate screw onto the diff and then that to the motor shaft. Maybe even a slipper clutch could be implemented with this setup?

This would work also, but would require even lower diff gears to multiple the available torque.

Enlarge the hollow output shaft and use a flange that bolts to the diff housing.

Here's an inrunner that impresses me and makes me curious. If it weren't so spendy, I would have one. It's "only" a 8 pole though. LOL

http://www.aero-model.com/Hacker-Hel...0mm-720mm.aspx

Oh, that sounds good. But what is the second bearing supporting? Doesn't make sense putting a bearing in the middle if it's to support the rotor? Am I missing something?

It's to eliminate flex.

You don't want the diff housing and the larger span trying to tame the magnetics of the motor, do ya?

Hmmm............trying to visualize everything here.

If the diff housing were thick aluminum, and the bearing on the diff end was enlarged, then the center bearing wouldn't have to support the endbell at all.

Two shaft bearings inside the motor would help hold everything true.

Ok, place the magnets on the outside of the diff case, and use a oversized can with the windings on the inside as an inrunner does. The can would be solidly mounted and the "diff/stator" would ride on bearings that are suppored by the ends of the can. In reality the endbells of the can could be made as bulkheads, and the center of the can would be removeable with the windings attached. 1/4 turn design would make removing one endbell easy, just pull the 4 chassis mount screws (2 in each bulk) turn 1 bulk 90deg and remove the stator/diff. Have one end of this stator/diff unbolt and you can service the diff as easily as a regular diff. Solidly mount the other bulkhead to the can, maybe with screws. This would allow kv chages easily, as only the center section of the can would need to be removed, or make it completely modular like a novak motor.

Multipole woould be required, and the diff height would be taller, as would the center drives. Worm drive ft and rear diffs with top output and bevel gears (think dump truck axles) would allow for more reduction and higher center driveline angles without raising weight too much. Place the rx/servos below them to offset this. Chassis could be narrow due to center motor mount and saddle syle trays with lipos split into series packs. Center motor/diff could also be placed front or rear for desired weight bias.

Aside from the added complexity of the center section and multi gear diff assemblies it would offer alot of benefits. Solidly made al or fiber reinfored plastic (carbon fiber?) front and rear diff bulks would be required to keep the worm drives meshing well. Off power coating would not be doable, unless you use one way bearings between the diffs and the wheels. Or you could use a gear reduction with std gears in the diffs, with a bevel output to direct the flow back to the center assembly. Seeing as these could be made smaller, and sealed it would be better than a center diff with exposed gears, even though it is more complex.

Of course a reduction could be applied to each end of the center assembly's outputs, and sealed. This would aloow std front and rear diffs and still not wear like an exposed setup. Gears could be spiral cut to improve effecintcy and strength and thus be made smaller. Still more complex that what we currently run.

For the inrunner concept... I think you'd basically need a cu$$$tom motor. :lol: I think the picture is pretty self-explanatory.

http://i52.photobucket.com/albums/g4...ffinrunner.jpg

Yeah man! Great idea, maybe not doable any time soon with our R&D access, but doable. Although, I am not too keen on using warm gears for anything R/C however, I just don't like them. This idea though having the diff being physically built into the motor housing is awesome, and on each end of the chassis you are saying? I don't think you would even need warm gears, as you can really do anything with motors, increase torque, lower speed, yada, yada.

Sike, ya, I think a sufficiently thick alum. plate screwed to diff housing then if the motor shaft was keyed, or squared, or splined..... then it would just slide in and be supported by the motor shaft, which because of the fact that it would be over sized from the increased size hollow shaft then it would be fine maybe.

Wicked man, I was like perfect solution. But then I am wondering how we screw the large motor shaft plate to the diff housing. This is one PITA of a problem. :whip:

The yellow area is the center diff. The little black rectangles are "screws". :lol: There are a few things missing. I left out the "wall" of the diff that houses the bearing, which would be between the red rotor and the blue pinion.

Ya, okay but how do we thread the screws in? :whistle:

Funny, after seeing B4maz X2 vehicle I had a glimmer of an idea like yours zpb. You've taken it a fair bit further

http://lh3.ggpht.com/_3N0hwXEVK9I/SO...0/IMG_0427.JPG

Sure you may need to create some space for the screw heads but why don't you think What's_nitro? idea would work?

PBO is that you street basher for idle wednesday arvo's :rofl:

Looks like some serious power in there! Strictly speed runs or something else? Do you have a diff in it. If so we need the full monty. :tongue:

No, it will work, and it's exactly what I have in mind, it's just the troublesome coup,ing of the motor to the diff housing. Observe the DIFFiculty (really no pun intended ;) ) in getting the screws into the diff from the motor side.

I think CEN (I might be wrong) has a metal diff cup and it opens from both sides. It would make things easier then the conventional plastic diff cases.

@ zpb, I was thinking you'd go the other way, from the diff toward the motor. Probably need a customer diff cup but at least assembling would be as normal as possible?

@ pinkpanda3310, it's not mine but when I saw it I thought of a diff each side

The screws need to go into the coupler from inside the diff cup. :yes:

Alright, I guess I am not too familiar with 1/8 differentials as I have not yet owned one, this project is for one however.

So, could you guys post some links or pictures to diffs? I am only familiar with Traxxas garbage... I recall a diff that can be opened from either end like Luc mentions, but I also can't find anything on CEN diffs.

Maybe a diff housing could be modified even to thread in from the diff side, if not already?

http://www.rcplanet.com/ProductDetai...GS001&CartID=1
http://www.rcbasher.com/savcendiffs.html

Hope that helps.

How stupid of me. Here's a nicer example:

http://www.rc-monster.com/proddetail...diffcup&cat=40
http://www.rc-monster.com/proddetail...aplarge&cat=40
http://www.rc-monster.com/proddetail...iffcapt&cat=40
http://www.rc-monster.com/proddetail...Msldiffrebuild

Great, thanks Luc. Those look perfect.

Now for starters I think I should do the outrunner idea first as this idea is not really proven yet, so no sense in getting Neu to make a custom motor... yet.

I think a plate can be machined and screwed onto the outrunner body, then these diff housings screwed into place on the plate from the diff side.

The Scorpion 4035 - 460Kv. I think is what I had in mind? IIRC, I would run it on 6s lipo, and with a truggy setup would equate to a ~40mph top speed, perfect for my local track. (well, 120miles away...)

I have to get Alibre Design up and running again, I haven't used it in pretty well 2 years now. Might have to relearn how to use it. :oops:

I use Autodesk Inventor 9...and MS Paint. :rofl:

I really like Alibre CAD, it's very user friendly and is just as powerful as 'bigger' CAD programs like AutoCAD, Autodesk, etc. The bare bones CAD program is only $97 too. However, I haven't used it in awhile and I can't seem to get into my account, and Alibre gave me a new password but still no go. :neutral:

Alright, I got all the Alibre V10 downloaded, went to install, but it says I need JVM (java virtual machine) installed before I can install. I DL'ed the one at Alibre but it is the wrong version (I am using Windows 7 Ultimate), and just closes. I went to Java website to get it, but I can't seem to find JVM for Windows 7, all I can find if just 'Java'. Do I need VT enabled in the CPU (Core2Duo E8400) in BIOS?

ANY help is appreciated, just point me in the right direction, I am great with PC's, just not with this type of stuff.

http://www.java.com/en/download/manual.jsp

It's right there, either 32 or 64 bit flavors.

JVM = Java Virtual Machine. This is the engine that actual runs the compiled Java application. It is individually compiled for each OS/hardware as it is compiled to machine language. Java applications are compiled into intermediate language that is processed by the virtual machine. Same thing as MS' .NET and many other forerunners.

JRE = Java Runtime Engine. This is essentially the packaging from Sun (or Oracle or Sun or Oracle... joy) that contains the JVM. It is intended for consumer use.

JDK = Java Development Kit. This is the full monte, the JRE, source, tools, etc. for developing applications in Java.

Okay, I guess I already installed the latest JVM. Why is Alibre still saying that I don't have JVM installed?? :neutral:

I sent an incident report to Alibre about it, hopefully they reply back tomorrow about it. I should be able to get it running on Windows 7 don't you think?

Well I just noticed that Alibre DID in fact reply back to me and I never saw it until now. What they told me is that the V10 Alibre design I have is not compatible with Windows 7, and that I have to upgrade to V12. Well I guess that is not too bad, as it's only $97 to buy it. :smile:

I'll let you know when I get it up and running, although it might not be until next week.