Prototype 98-102mm Motor Mount - Mini-ZRacer.com Forums

Ronac · 2010.01.20, 04:09 PM

I’ve attached some pictures a motor mount I design and built myself. I call it the “Reverse Sidewinder” in reference to the side winder layout of slot cars.

The difference about this motor mount is that the motor position is fixed (no slots to move the motor). There is an idler gear (which does NOT affect the gear ratio) being supported by two bearings to adjust the meshing. The purpose of the idler gear is to change the direction of the motor rotation relative to the chassis. If we look at the car from the passenger side, the conventional motor mount has the motor spinning counter clockwise. With this motor mount, the motor spins clockwise. The reaction moment from the motor (which is opposite of the motor direction) now contributes to rearward weight transfer rather than forward weight transfer. Since one direction biases forward and one biases rearwards, the total change can be up to 15-20% in load on the rear wheels depending on the torque of the motor and gearing being used. The idea with this mount is to increase the rearward traction through on power sweepers. I found that the lack of rear traction with mod motors to be a problem so my motor mount is the solution to that.

The differential has been switched to the other side to prevent the user to have to swap the motor wires backwards.

dxm2 · 2010.01.20, 05:05 PM

Looks like a great modifciation.

How would you characterize the improvement? Slight improvement or Substantial improvement?

Ronac · 2010.01.20, 05:10 PM

When I first tried this mount with a Mazda LM body and an Atomic Stock R motor, I was able to power through the wide sweepers much faster than I was able to before. My setup has changed a bit since then and so has the track. I've been struggling a bit with the Lamborghini recently so my testing progress had been slowed.

I'll post a video later on to demonstrate the effect of the motor mount. Even with motor that isn't particularly powerful, you can visually see the motor mount moving down under forward acceleration.

ianc · 2010.01.20, 05:33 PM

Looks like a brilliant idea. Another head slapper.

In addition to loading the rear wheels more, it looks much easier to set the mesh via the idler gear rather than moving the motor in slotted holes.

I foresee two potential problems however; increased friction in the idler gear's bearings causing driveline loss, and possible slippage of the idler arm under load if the method of adjustment is not secure.

How do you prevent the idler arm from rotating?

Are you using standard wheel bearings for the idler gear?

What are your plans for the mount? Do you intend production and sale?

Great idea and execution!

ianc

Ronac · 2010.01.20, 07:06 PM

Adjusting the mesh requires you to only loosen one screw.

I do agree that there will be additional drivetrain losses. The amount that it adds is hard to say but there are bearings in there to attempt to reduce the rcition. As I've mentioned before, this mount is a bit more focused towards mod racers and with mini z's you can usually get more than enough power but the problem is putting the power down. So with more losses, you could potentially just use a more powerful motor to make up for it.

I've raced over 6 weeks with this motor mount and the idler arm coming loose hasn't been an issue I've used a bit of loctite on the screw and screwed it in very tight. It doesn't come off even in accidents. The friction from the screw will prevent the idler arm from swinging up.

As for bearings, there are two standard front wheel bearings that are buried inside the orange idler gear.

For plans for the mount, I've shown Pn and they seem to think the market for this mount wont' be big enough to justify a production run. Hopefully with some good results from a trusted test driver, that opinion might change and it can become available to the public.

ianc · 2010.01.20, 07:58 PM

Hi Ronac,

Thanks for the info. Hopefully Phil and co. will see this thread. If enough people express interest, it might change their mind,

ianc

Felix2010 · 2010.01.20, 09:14 PM

Ronac, I saw your reply on the other threadand I think I see what you are talking about reversing the torque from being biased towards the rear with your new mount than the front with a normal mount.

Keep up the good work bringing new ideas to the scene Ronac

Inventors are always welcome

color01 · 2010.01.20, 10:21 PM

As you might imagine, the market for a Mod-only motor mount is pretty small... so I wish you the best of luck in convincing PN. But as a one-off solution to the unique track conditions where you race, it is a good idea and well executed at that. How is your idler gear made? If you machine a spacer to put between the bearings in the idler gear, you may be able to get rid of the swing arm. Just have the axle slot into the motor mount and you can tighten the nut on the end of the idler gear to secure the whole assembly. If you give the end of the axle a rectangular shape to slot into the mount, like such,

Code:

 _
| |
|O|     (the "O" is the cross-section of the actual axle)
|_|

then when you tighten up the whole axle you can actually make a stiffer structure that what you have now, that will definitely not bend or shift when you apply Mod power through it.

MantisMMA · 2010.01.20, 10:41 PM

if you want to produce them seriously contact me and we can talk about it.

herman · 2010.01.21, 05:59 AM

pretty cool motor mount... can't wait to read the reviews... hoping and wondering when this will come out commercially...

herman · 2010.01.21, 06:00 AM

hmm... will a 90-102 version be available?

Ronac · 2010.01.21, 06:54 AM

color01: I wouldn't say that this motor is specifically for mod class since it could benefit anyone that lacks rear grip under acceleration. Although it is less of a problem with stock motors, it could still prove beneficial. Regarding you idea with a rectangular slot, I've though of trying that however I actually need two degrees of freedom (x and y) to adjust the mesh. Thats the reason the idler arm can swing around the screw and also slide along the slot on the arm.

Mantis + herman: I'm going to see how the thurough testing of the mount goes. If it proves to be a winner then I'll have a more serious look into production. However, I wouldn't mind getting a quote for a small run of these actually. Could you pm me and we'll figure something out?

Ronac · 2010.01.21, 07:12 AM

Here's a little teaser video

Sorry for the poor quality..

http://www.youtube.com/watch?v=Vm1QGhB1dqY

addicted · 2010.01.21, 09:48 AM

looks like a cool idea!

color01 · 2010.01.21, 10:01 AM

Quote:

Originally Posted by Ronac

color01: I wouldn't say that this motor is specifically for mod class since it could benefit anyone that lacks rear grip under acceleration. Although it is less of a problem with stock motors, it could still prove beneficial. Regarding you idea with a rectangular slot, I've though of trying that however I actually need two degrees of freedom (x and y) to adjust the mesh. Thats the reason the idler arm can swing around the screw and also slide along the slot on the arm.

I see your point, I was going to suggest a slot in the shape of an arc but there are different spur gear sizes to consider too...

The thing about stock motors is that you need to be smooth, i.e. the less weight transfer the faster you'll go, period. Your motor mount design deliberately accentuates the weight transfer response to throttle inputs, so you'll be hard-pressed to keep up with the standard-motor-rotation cars in stock. The drivetrain efficiency also hurts a lot. I'm not saying it can't be done, just that it doesn't make sense given that stock-motored racing has no traction problems anymore anyways unless your setup's REALLY off (in which case this motor mount ain't gonna save you).