reverse motor ?? possible ?
 

I've got a 17.5T sensored motor/esc installation that I'd like to reverse. It presently has the output shaft (and gears) sticking out the right side of the chassis. I'd like to run with the gears out the left side. That would shift the rear weight of the car to the inside of the turns. Without ballast, the right rear presently has 2+ ounces more than the left rear, exactly backwards from what I'd like the car to have.

It took a couple of minutes to switch the motor/gears/axle around. Getting the Spektrum TX to throttle/brake properly isn't working at all.

Simply reversing the throttle in the TX doesn't hack it.

It may be obvious that I've just started running RC cars. Got 50 years of flying models including electric. Unfortunately the radios are very different between cars and planes. To get my planes' motors to spin the other way takes swapping a couple of wires. They don't have sensored motors however. And simply reversing the throttle on my DX5C doesn't work either.

Is there a way to reverse the rotation of the (Reedy) motor/esc? Somebody at the track said he thought they could be reprogrammed. Reedy really doesn't have much info about their stuff. The info that came with them is really sparse.

tia

Not sure what type of RC car you are running but in order to reverse the motor you will need to add another idler gear to change the rotation. In a 2wd buggy like a b6.1, you can accomplish this with a 4 gear tranny that includes 2 idlers.

And also keep in mind that the handling of the car will be completely different if changing the orientation of the motor. This is due to the fact that the motor will be spinning the opposite direction and the gyroscopic effect will cause the vehicle to behave differently.

Some motors these days allow for you to set your rotation within the ESC with a Programmer, provided you are running a setup (Motor & ESC) that will allow for this as a normal operation. In the programmer it will ask for CW or CCW rotation. You can also on some just simply switch the two outer wires on the esc to unsensored motor wiring.

^ That only works on sensorless motors. Do not try to swap motor wires on sensored motors. You have to keep A to A, B to B, and C to C.

On a 17.5T motor, there is no good way to reverse the motor because of the sensors. They normally have an adjustment range from 0 to 45 degrees and if you have it at +20 degrees timing and reverse the output of the motor in the ESC settings then suddenly you are running -20 degrees timing. I don't know of any 2 pole motor that has the ability to run a negative motor timing to allow for reverse rotation. It would take a custom back endbell for your motor to align the sensors.

"Simply reversing the throttle in the TX doesn't hack it."


Why?

R1 new ESC has a the ability to change motor direction. I never tried it. You can contact them on their facebook page.

Because the TX's trigger function is what gets reversed. When you squeeze the trigger to accelerate forward, the brakes are applied, but of course the wheels aren't spinning yet. The trigger functions are reversed which isn't what you need to happen.

My Spektrum TX's reverse function reverses the TX's trigger functions, not the motor.

Looks like I need to find a sensorless motor/esc.

The present setup uses a 17.5T. Do I simply look for any sensorless with the same KV rating to find a straight swap?

I'm just getting into carpet oval. There are two excellent ones that have good turnouts for Legends. Neither of them enforce any rules to speak of. They allow the break-out format to take care of that. It suits me just fine. Everyone suggested the perfect motor was a 17.5T because... well, just because about sums up the suggestions. Funny thing is one track is the Rug. From what I can tell about carpet ovals, it's maybe the longest oval on the East Coast, and most certainly within my reach. The funny thing is the other track is MUCH shorter. The two extremes of what I'll probably ever see, near as I can tell.

I've worked out that my Legends gearing gives about 2.0-2.5" roll out. At the short track, my TX's throttle range setting is about 45%. At the Rug, it's around 80%. I'm guessing the gearing misses being efficient somewhat at the Rug and really inefficient at the short track. I'm also guessing the 17.5s aren't close to being the most appropriate for the track combination. Or maybe it's the gearing.... or...…. anyway....

I don't see the choice of sensor/sensorless as being important to me right now. But also don't have a clue how to pick a sensorless that matches a 17.5T, or whether or not that would be a smart thing to do anyway.

I'm rambling.... right.....
So let me shift gears and simply ask a few questions....
Any reasons to try and find a sensorless that performs like a 17.5?
Are there any?

Anything I put under my Legends' bodies is going to pass tech. I'm enjoying looking for the smartest parts to put under them.
thanks for any help offered

Changing direction of motor and ESC. High end ESC like Tekins and Castle by Hotwire(Tekins) and Castle( program card). Brushles motors are easy to change direction like brushed motors. Bruskless motors has 3 wires A, B,C.. B wire mostly Grd. Switch wire A-C, and C-A, Cross them over. That will change motor direction. All RC hobbyist know that. Racing Drone we do that in every build. Good luck and have fun.

Now that you've explained this is for a Legend and why you want to do this, I'll offer some hints:
1) For breakout is is more efficient to run a higher KV motor (than the 17.5) geared much lower. The average current draw is less, draining the battery less, and thus your lap times will be more consistent from beginning to end of race.
2) Try a 4 or 6 pole 3300 KV Dynamite Tazer sensorless motor - you can change rotation by swapping two wires. The KV is much higher than a 17.5 but that goes with suggestion #1

Just a little FYI, the B wire is not ground. You can switch any two wires on a sensorless motor to reverse the motor direction. A<->B, B<->C, or A<->C, it doesn't matter.

Very simplified explanation of a brushless esc/motor: The ESC connects one of the three wires to ground and one of the three wires to +in to move the motor. Then moments later connects a different pair. Another moment later it connects a different pair of wires. It times the changing connections perfectly in time to the position of the motor to make it spin. There are 6 different steps to the cycle and at any time and of A, B, or C could be connect to +in or ground.

OK, I've got something to test. Got a sensorless motor and esc installed. The motor is rated 3300 kV. Got no idea how it should compare to the 17.5T because none of those I've got have listed a kV value. In fact, I've only seen one list that gave kV estimates for "turn"T motors and have yet to see any sensored motor advertised that listed kV.

thanks for the posts