2LikesMid motor vs rear motor for U.S. Tracks
08-29-2013, 10:54 AM
#61
This is only true if he molded part is made in high enough volume. As you point out, mold startup is too expensive to amortize the cost into a low volume part and still come out lower than small-batch alloy or c/f plate.
08-29-2013, 11:02 AM
#62
I am glad I found this thread because I have always wanted to use my mid engine set up but am always told don't do it! I think it has to do with driving style mainly and I think mid would be a lot more stable for a driver like me who drives way to aggressive on a half clay half dirt track.
I will have to put it to the test for real this time
I will have to put it to the test for real this time
08-29-2013, 11:04 AM
#63
I am glad I found this thread because I have always wanted to use my mid engine set up but am always told don't do it! I think it has to do with driving style mainly and I think mid would be a lot more stable for a driver like me who drives way to aggressive on a half clay half dirt track.
I will have to put it to the test for real this time
I will have to put it to the test for real this time
08-29-2013, 11:04 AM
#64
Tech Regular
I've been out of RC for a good 15 years and the mid-motor just makes sense to me as an engineer and I'm re-entering with an X6sqrd and an SCX-60CF from x-factory.
I've got a long ways to go with driving but the car is a lot faster than me as a driver right now. I definitely don't have rear grip issues.
I've got a long ways to go with driving but the car is a lot faster than me as a driver right now. I definitely don't have rear grip issues.
08-29-2013, 11:07 AM
#65
I dont think rear "grip" is the issue with xFactory. From what I have read and talked to people about, its fine until you lose traction, then its more severe. Yes, everyone always says that MM makes more "sense" from an engineering standpoint. But on lower bite tracks it has never proven its self. If it ever does, then maybe it will become the standard like it is in europe on astro turf. Dont real dune buggies have the motor in the rear?
08-29-2013, 11:14 AM
#66
Suspended
That said, with the high grip of the worlds, and Naoto's 1/12th scale background, he will be a serious contender for the win. We'll see if the other guys can do it honestly.
08-29-2013, 03:53 PM
#67
The thing giving mid motor forward traction is the very thing giving it on power push in corners and decreases braking ability. It's the 4 gear gearbox. I firmly believe this to be a mistake in mid motor car design after having run mid motor over the past year. A 4 gear allows so much weight to shift rearward that you have tons of forward traction. My biggest problem was a car doing backflips on acceleration from too much traction. When you get on power in corner, that weight shift appears in the form of push since the front wheels that actually steer are unloaded.
.
.
08-29-2013, 04:07 PM
#68
Tech Master
08-29-2013, 04:20 PM
#69
The weight transfer due to accelerating the CG of the car is the same for mid or rear motor. The direction of this weight transfer is not affected by the number of gears in the transmission.
These two mechanisms are not the same and they both happen when you accelerate.
Last edited by otter; 08-29-2013 at 04:20 PM. Reason: typos
08-29-2013, 05:06 PM
#71
Do what I did! Make your own!
Mid motor works better than people give it credit for. There is a metric tonne of mid motor setup info on this forum and if you can locate and apply that knowledge you can end up with a deadly fast car, no matter what the track surface.
Mid motor works better than people give it credit for. There is a metric tonne of mid motor setup info on this forum and if you can locate and apply that knowledge you can end up with a deadly fast car, no matter what the track surface.
08-29-2013, 05:30 PM
#73
There is a reaction torque to the motor rotor angular acceleration. Either you will get more reaction force down on the rear wheels and up on the front, or the opposite, depending on which way the motor is spinning. The difference between these two cases is three and four gear transmissions.
The weight transfer due to accelerating the CG of the car is the same for mid or rear motor. The direction of this weight transfer is not affected by the number of gears in the transmission.
These two mechanisms are not the same and they both happen when you accelerate.
The weight transfer due to accelerating the CG of the car is the same for mid or rear motor. The direction of this weight transfer is not affected by the number of gears in the transmission.
These two mechanisms are not the same and they both happen when you accelerate.
08-29-2013, 05:38 PM
#74
The weight shift is no different than found in rear motor cars. The reason for the 4-gear was to orient the motor's rotation the same way as a rear motor car. All other things equal, a mid-motor car has less on power pish than a rear motor because their is more weight in front of the rear axle. If a mid car is pushing on power then it should be a correctable setup issue.
08-29-2013, 05:43 PM
#75
The thing giving mid motor forward traction is the very thing giving it on power push in corners and decreases braking ability. It's the 4 gear gearbox. I firmly believe this to be a mistake in mid motor car design after having run mid motor over the past year. A 4 gear allows so much weight to shift rearward that you have tons of forward traction. My biggest problem was a car doing backflips on acceleration from too much traction. When you get on power in corner, that weight shift appears in the form of push since the front wheels that actually steer are unloaded.
This accentuated weight shift is also apparent on braking. The weight instantly shifts forwards when you get off the throttle. This unloads the rear wheels which are the only ones that brake. With less effective weight on the braking wheels it has a tendency to lockup sooner but overall decreases braking power.
The main problem with mid motor has nothing to do with where the motor is located and everything to do with the percentage of weight on the rear wheels. Mid motor cars have far less than rear motor cars. Rear motor cars have too much. We are constantly trying to add weight forwards and use high levels of anti squat and this is with a counter rotating motor to wheel rotation. The X6 has more static weight on the rear wheels than other mid cars which is why it works better but still suffers from the flaw of the 4 gear setup which is unfortunately being touted as the secret to making mid motor work.
I'd rather see a mid setup with the engine sideways like 4wd cars so that their rotation is offset by the spur and slipper. I want a car with no artificial weight shift from the motor. Then I want to see a static weight distribution if about 68% weight on the rear wheels with that weight within the wheelbase. A car that can do that will change lots of minds about mid.
This accentuated weight shift is also apparent on braking. The weight instantly shifts forwards when you get off the throttle. This unloads the rear wheels which are the only ones that brake. With less effective weight on the braking wheels it has a tendency to lockup sooner but overall decreases braking power.
The main problem with mid motor has nothing to do with where the motor is located and everything to do with the percentage of weight on the rear wheels. Mid motor cars have far less than rear motor cars. Rear motor cars have too much. We are constantly trying to add weight forwards and use high levels of anti squat and this is with a counter rotating motor to wheel rotation. The X6 has more static weight on the rear wheels than other mid cars which is why it works better but still suffers from the flaw of the 4 gear setup which is unfortunately being touted as the secret to making mid motor work.
I'd rather see a mid setup with the engine sideways like 4wd cars so that their rotation is offset by the spur and slipper. I want a car with no artificial weight shift from the motor. Then I want to see a static weight distribution if about 68% weight on the rear wheels with that weight within the wheelbase. A car that can do that will change lots of minds about mid.
P.S. If that worked the concern wouldn't exist in current 2wd cars.
Last edited by Dave H; 08-30-2013 at 12:11 AM.