2010.01.21, 10:20 AM
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#16
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Registered User
Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
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Quote:
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.
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It doesn't accentuate it, merely reverses its direction.
The drivetrain efficiency thing might matter with stock motors, but as Ronac says, it's primarily for mod, and with powerful motors the trouble is getting the power to the track, so it shouldn't be an issue in that regard...
ianc
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2010.01.21, 11:47 AM
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#17
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Registered User
Join Date: Aug 2002
Location: Burnaby, B.C.
Posts: 222
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I did some testing with this motor mount yesterday at the track. We use the smooth side rcp and I was using the 20 AW tires in the back. What I found was that I used a slightly different driving style than normal. It's actually a bit similar to driving a MA-010 in that you can turn in and control the turning radius with mostly the throttle. When I can drive like that, I find that I can hold the driving line that I actually want much easier. Regarding the weight transfer upsetting the car, I was actually able to drive the car pretty recklessly without having it spin out on me at all. I could literally just let off throttle, turn in hard and power on (the right amount ) to hold the line.
Anyway, I'll be sending off this prototype off to San Jose for Tj to try out and do a comparison with a regular style mount. Hopefully then I'll have a more unbiased list of pros vs cons of this mount.
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2010.01.21, 12:54 PM
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#18
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Registered User
Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
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One other thing strikes me: if the user didn't mind reversing the motor wires on the board or motor, then the setup could work similarly with everything else stock and as-is provided an existing motor mount could be modified to accept an idler gear to reverse the direction of rotation.
This would mean that a custom motor mount need not be manufactured, only the idler gear and arm. Might be much easier and cheaper to get into production if only the gear, bearings and mounting arm were needed.
Perhaps a reduced cost option for people willing to do the modification themselves? You'd have to test with different motor mounts to see what could be worked out...
Just a thought...
ianc
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2010.01.21, 01:10 PM
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#19
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02-Racer
Join Date: Sep 2004
Location: Belgium - Holsbeek
Posts: 949
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There was a setup with belt for Mini-Z, this has the same effect.
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2010.01.21, 01:16 PM
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#20
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Registered User
Join Date: Aug 2002
Location: Burnaby, B.C.
Posts: 222
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ianc: I've actually though about modifying an existing pod before I resorted to build my own from scratch. The problem is, the normal pod just don't have the clearance required for the idler arm.
HaCo: Yup the belt drive system does achieve the same effect. I've also considered going the path of a belt drive but I found that with the same motor to diff spacing, I couldn't quite get the same range of gear ratios as I could with the gears. I would be interested to compare the drivetrain losses associated with both systems.
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2010.01.21, 02:10 PM
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#21
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Registered User..Of What?
Join Date: Jun 2009
Location: S.F. CA.
Posts: 89
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you have a Great test driver with the talent to evaluate.
all the Best to you Ronac
D
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2010.01.21, 02:25 PM
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#22
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Registered User
Join Date: May 2006
Location: Los Angeles
Posts: 375
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Not quite convince there is enough of an advantage yet.
When I first heard about it, did a quick check on how much effect it will have. It was something like a gram more force on the rear tires. Verified it by taking the pinon off and running car with rear wheels on a scale. It gained about less than a gram or so when accelerating with a mod motor.
Mainly, 3 things will happen during acceleration. The pinion will try to "climb" up the diff gear. This will lift the front of the car up for more rear wheel traction. That effect will be there no matter which side motor is on.
Second thing is with the acceleration of the rotor in the motor, it will twist the motor mount. This will lift up the rear end of the car with the new mount. However, only during the split second that the rear end is being lifted up that you gain some more traction due to inertia of the chassis being lifted up. After that, it will be just as if you raise the ride height of the rear end.
The third thing is during steady state acceleration, the acceleration of the rotor will put a backward rotating torque on the chassis that put more force on the rear wheel while the motor rotor is accelerating. This is the most useful performance gain, but due to the size of the rotor in this scale, the effect is minimal. You just as well put an extra gram of weight in the back of the car.
It may be worth a try anyway. I actually drew up an adaptor plate to fit a pinion on the motor plate of a 94mm mount, but haven't given it to PN yet.
Just for curiosity, may be I will run a simulation at work next week after work. We have a dynamic simulation program that Ford and some race teams use to run simulation on suspensions among many other uses for other industries. It will tell you the whole story (If you set it up right).
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2010.01.21, 03:40 PM
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#23
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02-Racer
Join Date: Sep 2004
Location: Belgium - Holsbeek
Posts: 949
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The Turkish drivers that did the beltdrive system also said that because the motor turned in a different direction, the timing of the motor was different.
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2010.01.21, 03:46 PM
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#24
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02-Racer
Join Date: Sep 2004
Location: Belgium - Holsbeek
Posts: 949
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It were the TGR guys:
Wonder what happend with these guys?
Anyway, the thing you made looks really good, always nice if ppl make stuff by themselves!
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2010.01.21, 04:12 PM
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#25
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EMUracing
Join Date: Oct 2004
Location: NYC
Posts: 7,417
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Looks like an interesting mount.
Ben, great response.
I look forward to reading about this more, I have thought about trying the belt drive for this reason, but at the same time, if you are adding rear grip, wouldnt that reduce steering on power? I may actually prefer to gain steering on throttle, and gain rear grip off throttle. Which should give a more consistant feeling of how the car takes the corners. It should allow me to brake later into the corner, and accelerate sooner after the apex.
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EMUracing
Micro RC Syndicate /DG Designs /GSR /Reflex Racing /Fast By Faqish /MurderTown Racing
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2010.01.21, 04:32 PM
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#26
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Registered User
Join Date: Aug 2002
Location: Burnaby, B.C.
Posts: 222
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The problem with the method you used to test the effect is that with no load on the motor, there will be minimal reaction force. Every force has an equal and opposite reaction force. With the pinion in place and having it on the ground, the load on the motor will be substantially greater and so will the rearward weight transfer.
The only way to test this somewhat accurately is to have the car on weighted rollers and accelerate on there while the rear wheels are on a scale.
Regarding the first point, I agree. Having the gears on the left side and right side offer no differences at all. The reason for me doing so is so that the user doesn't have to wire the motor backwards.
There are 2 forces at play when under acceleration. One relates to what causes a car to do wheelies. Thats just the torque from the wheels accelerating the car. That torque is equal to the torque of the motor multiplied by the gear ratio (5:1 for example). The other force is the reaction from the motor. For a normal motor mount, assume transfer is 100%. The reaction negates ~20% (1/5) of this because the reaction torque is about 20% of the drive torque. With the sidewinder mount, the 20% torque is added to the 100% drive torque. So in essence, you're going from ~80% to ~120%. That could be up to 50% difference in weight transfer.
Just a little side story, the reason I got this idea is from an idea from Nascar. There was a team that built an engine that rotated opposite from the competition. This actually allowed them to transfer more weight to the outer wheels and they were cornering at speeds much faster than the competition. Although you may think the effects are negligible, every little bit counts when you're in competition.
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2010.01.21, 04:46 PM
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#27
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Registered User
Join Date: Aug 2002
Location: Burnaby, B.C.
Posts: 222
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To elaborate a bit more on your testing method. Imagine just holding a motor and accelerating. You'll feel a bit of a kick back but not very powerful. Now do the same but hold the pinion gear with your other hand. Now you're feeling the full reaction torque that would be produced when the car is under acceleration.
HaCo: I not sure if I'd rather have the motor spin backwards or not. They claim that it will benefit because of the advanced timing but is that the case for all motors? I know for a fact that the Atomic Stock R is made specifically to spin the "right" way.
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2010.01.21, 05:19 PM
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#28
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PN RacingTEAM Driver
Join Date: Jul 2007
Location: southern calfornia
Posts: 1,530
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i have a few questions?
is there any additional drag due to the extra gear?
does it affect acceleration due to the additional friction or mass?
how does a TOP shock affect this set up?
is it affected by pod angle?
info is appreciated
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2010.01.21, 05:27 PM
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#29
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Registered User
Join Date: Aug 2002
Location: Burnaby, B.C.
Posts: 222
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To be honest, yes there will be extra drag to the drive line. I would think it is very minimal though because of the inclusion of bearings. I've raced mine against another racer with the same gearing and motor and the speed is exactly the same. Top shock works perfectly fine with this motor mount. I've had it with the new dual spring PN shock and no clearance issues at all.
Not quite sure what you mean by pod angle. Could you try to explain a bit more into that?
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2010.01.21, 05:45 PM
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#30
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PN RacingTEAM Driver
Join Date: Jul 2007
Location: southern calfornia
Posts: 1,530
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Quote:
Originally Posted by Ronac
To be honest, yes there will be extra drag to the drive line. I would think it is very minimal though because of the inclusion of bearings. I've raced mine against another racer with the same gearing and motor and the speed is exactly the same. Top shock works perfectly fine with this motor mount. I've had it with the new dual spring PN shock and no clearance issues at all.
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id like to know if the top shock affects the grip at all...with or with out the rebound spring
Quote:
Originally Posted by Ronac
Not quite sure what you mean by pod angle. Could you try to explain a bit more into that?
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(when on the car stand the t plate holds the motor pod flat. when u set the car on to its wheels u will get some droop and reduce the ride height, i will call that negative angle
if u add the top shock and add a bit of preload it will push the pod and increase the ride height i will call this positive angle.)
does the effect change with positive/ nevative pod angle?
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