Electric Motor Mounting/SLEC Electric Fun Fly

[Scruffmeister]

I'm after a bit of advice to clear up confusion in the SLEC Fun Fly Electric build instructions - in summary, do I use captive nuts or not to mount the AXI 2826 motor on the ply firewall using the cross-mount? The motor itself comes with a mounting kit like the black-cross in this photo.

The included instructions are for the IC version, with an addendum for the electric version. The IC version uses captive nuts as you would expect in the firewall. The electric version make no mention of this. I assume the intention is to use nut/washer + bolt to secure the radial mount to the ply firewall. What's "normal" for electric models? Here is a photo of the motor mount box dry assembled:

Thanks

Edited By Scruffmeister on 25/11/2013 19:03:31

[Tim Mackey]

Normal? Electric flight?? LOL

It doesnt really matter which mount you use, the kit /motor one - all that matters is whether you are "rear mounting" the motor and letting the whole can and prop driver revolve "outside" the box mount, or whether it will fit inside the box. If it all suits the arrangement chosen, then no reason not to use the captive nut system.

However, my guess is that you will fit the motor inside the box, and then you could simply use threaded screws through the front plate (firewall) and into the motor front section....secured with a LITTLE threadlock. This may necessitate drilling four correctly positioned holes in the firewall. Be sure the screws are not so long as to possibly foul the windings, and ensure the lead out wires and can are not fouling anything either.

Edited By Tim Mackey on 25/11/2013 19:21:07

[Pete B]

Looks like the front of the leccy mount is pre-drilled for the X-mount. I assume the motor will be contained within the ply box, Scruff?

If so, and the shaft is extending from the static end of the motor, first attach the X-mount to the motor, using the 4 countersunk screws through the inner holes of the mount. Put a touch of blue threadlock on the threads of each.

Next, I'd use 3mm nuts and bolts to attach the X-mount to the front of the ply box, with a flat washer on the outer face and a spring washer/threadlock and nut (or Nyloc nut) on the inner surface. I like threadlock.....

I see you have some tri-section strip to support the joint - I'd add some to the inside front corners of the box and the outside of the box to strengthen the firewall joint further.

You'll need a collet-type prop adaptor for this method of mounting. The prop adaptor in the above picture won't be used as it is designed to fit the rotating half of the motor.

Depending on the model and the length of the nose, it's possible that the motor can be fitted to the front of the ply box, too. I'd use the same mounting method if that's the case. The prop adaptor above would normally be used in this case, although you may prefer to push the shaft through and use a collet-type prop adaptor.

Hope this helps...

Pete

Blimey, took longer to type than I thought and Tim's got in first   Yes, that too is a method I use - I was  trying to avoid the hole-drilling stage on the KISS principle.....

Edited By Pete B - Moderator on 25/11/2013 19:33:31

[ken anderson.]

SM....mount the black cross mount on to your motor with the countersunk screws,,,and then the crossmount to the ply firewall/box.....the shaft of the motor will be going through the hole in the ply box rear........then fit the prop adaptor to the motor complete with the prop.............if you wanted to use a different configuration --- you would have to reverse the shaft in the motor and fit a 3rd party prop adaptor......and as tim say's use some thread lock on the countersunk screw's and ......I use clear silicone on the nuts that fit the mount to the ply box....in case they decide to escape...

ken Anderson ne..1 ....motor mount dept....

[Andy48]

Normally for electric models, the ply box is a spacer and you mount the motor on the front of the ply box, not in it. The captive nuts are secured behind the front of the ply box.

[kc]

It seems to me as though the question being asked is whether the motor goes in front or behind the ply wood bulkhead.
If that is the query then assemble the cross mount onto the motor and see which end the shaft protrudes. Then try the motor onto the plywood and see if the plastic cowl looks like it will fit.
If we see a photo of motor & cowl we can say which type of prop adaptor will fit ( i.e. the one you showed or the shaft mounting type)

[Scruffmeister]

So... this has been slightly misunderstood. No motors are going inside the box and it will be rear mounted with the entire can rotating. The instructions show that the motor goes in-front of the ply box and this is the exact motor and mount set used on the SLEC prototype, i.e. the box itself is a spacer. The cross-mount will be used to affix the motor to the box, the prop adaptor shown in the picture above will be used.

The question really was: "do I need to use captive nuts, or is a bolt + nut and washers sufficient to secure the cross-mount to the front of the ply box"

[stuey]

I would say nuts bolts and washers are fine if you can get to them to tighten them up. A drop of medium threadlock would be good too.

[Andy48]

Posted by Scruffmeister on 25/11/2013 21:17:29:

The question really was: "do I need to use captive nuts, or is a bolt + nut and washers sufficient to secure the cross-mount to the front of the ply box"

Captive nuts have a larger surface area than washers, and therefore I would use the former. The plywood will compress more if you use washers and the motor mount could become slack.

[Biggles' Elder Brother - Moderator]

Use bolts and washers and a drop of blue locktite - no problem. And no prongs digging into your plywood either!

BEB

[Pete B]

Posted by Martin Phillips on 25/11/2013 19:37:30:

Normally for electric models, the ply box is a spacer and you mount the motor on the front of the ply box, not in it. The captive nuts are secured behind the front of the ply box.

Normally but not invariably, Martin. It depends very much on whether the cowl is long enough to allow fitting in front of the box. My Phoenix Rainbow has the motor within the box and I'm sure there are others.

Given that many of these boxes are 1/8" ply or thereabouts, I'd rather use suitably-sized washers than captive nuts to spread the load and avoid penetrating the ply. With threadlock and spring washers, I've not had any failures.

We're a broad Church!

Pete

[kc]

If you use captive nuts they will go on the outside with the mounting as described and then screwdriver access would be needed from inside the box unless hexagon head bolts are used.
It might be easier to use nuts inside and any type of bolt from outside.

Edited By kc on 26/11/2013 10:51:17