Motor mounting

[Sid Dennis]

I have pretty well no experience with electric aircraft. I have been trying to find stuff out but it is very confusing at times. The latest thing I have seen is where the prop on a outrunner is mounted on the case/can and not the shaft. So in a way the motor is mounted "backwards" . why is this done and does it matter?

[Keith Berriman]

Some motors have reverseable shafts to assist with mounting in the bulkhead in the model some motors have the method described as above so you don't have to reverse the shaft. I think its done this way so as not to upset the balance of the motor that the manufacture checked at the factory

[Geoff S]

One big advantage of mounting it that way round is that the connecting wires are already at the back and don't have to be fed out perilously close to a fast rotating outer case. The disadvantage is that the bearings are overhanging but in the size of motor I've used (up to the equivalent of a 40/50 size glow) it doesn't seem to have been a problem.

My current build uses the rearward mounting on a bigger motor and will draw up 60 amps whilst driving a 16x8 prop, so quite big. I still think it will be trouble-free in that respect.

Geoff

[Andy48]

I had one scary occasion when the prop flew off from an electric motor, due to the prop adaptor not being secured tight enough/far enough on the shaft. Ever since I have always used the type of prop adaptor where the adaptor is screwed to the can. Much safer!

[onetenor]

the guy is trying to understand the difference between in runners and out runners not the orientation of the mountings i.e.an outrunner s the opposite of an inrunner hence his allusion to it being backwards .He really means one is the opposite of the other.   IIRC out runners deliver more power than inrunners 

Edited By onetenor on 27/11/2017 12:45:55

[John Emms 1]

Posted by Sid Dennis on 27/11/2017 10:38:14:

I have pretty well no experience with electric aircraft. I have been trying to find stuff out but it is very confusing at times. The latest thing I have seen is where the prop on a outrunner is mounted on the case/can and not the shaft. So in a way the motor is mounted "backwards" . why is this done and does it matter?

The original outrunners were intended that the shaft sticks out of the front with a prop adapter on the shaft. This means that the loads of the prop bear directly on the big bearing in the mounting face.

The radial mount set came as a result of people wanting a motor to be fitted on the front of a bulkhead, and it was a Chinese company that first came up with the solution. Unfortunately the company that came up with this did not re-design the motor, so the prop loads now bear on the tiny bearing at the back that is cantilevered on a relatively weak alloy tube (supporting the end of the rotor). For the greatest durability, the real answer is to mount any motor so that the prop is mounted on the shaft, with the motor behind the mounting plate, but I have mounted outrunners "the wrong way" for convenience with models that have been converted from IC.

With collet type prop adapters, drill out the prop hub to allow the collet to fully move through the prop driver, and grip without being stopped by the prop hub. Using a TINY amount of grease on the taper of the collet allows the maximum force to be used to grip the shaft, but of course, do not allow any grease on the shaft!

Hope that helps

[Sid Dennis]

Thanks for the info guys. My question was indeed mounting prop to shaft OR motor body. Probably the ONLY thing that is clear so far is the difference between inrunners and outrunners!!!! : )

[Andy48]

Posted by John Emms 1 on 27/11/2017 12:53:06:

The radial mount set came as a result of people wanting a motor to be fitted on the front of a bulkhead, and it was a Chinese company that first came up with the solution. Unfortunately the company that came up with this did not re-design the motor, so the prop loads now bear on the tiny bearing at the back that is cantilevered on a relatively weak alloy tube (supporting the end of the rotor). For the greatest durability, the real answer is to mount any motor so that the prop is mounted on the shaft, with the motor behind the mounting plate, but I have mounted outrunners "the wrong way" for convenience with models that have been converted from IC.

I think you are viewing this from the experience of just one manufacturer some time ago. Now most motor manufacturers offer both prop mountings. I use Turnigy SK3 with the prop adaptor bolted to the can, and I've never had any problems with bearing, in fact just the opposite, the motors run as quietly as the day they were first fitted.

[onetenor]

My apologies I misunderstood

[Frank Skilbeck]

Posted by Andy48 on 28/11/2017 11:18:39:

Posted by John Emms 1 on 27/11/2017 12:53:06:

The radial mount set came as a result of people wanting a motor to be fitted on the front of a bulkhead, and it was a Chinese company that first came up with the solution. Unfortunately the company that came up with this did not re-design the motor, so the prop loads now bear on the tiny bearing at the back that is cantilevered on a relatively weak alloy tube (supporting the end of the rotor). For the greatest durability, the real answer is to mount any motor so that the prop is mounted on the shaft, with the motor behind the mounting plate, but I have mounted outrunners "the wrong way" for convenience with models that have been converted from IC.

I think you are viewing this from the experience of just one manufacturer some time ago. Now most motor manufacturers offer both prop mountings. I use Turnigy SK3 with the prop adaptor bolted to the can, and I've never had any problems with bearing, in fact just the opposite, the motors run as quietly as the day they were first fitted.

Me too, I have an 1800 watt 8s set up running like this for several years, no issues.