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Author Topic: Electric Crutch  (Read 2106 times)

Offline Mike Palko

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Electric Crutch
« on: August 17, 2022, 09:05:42 PM »
I recently converted an IC ARF SV-11 to electric using an “electric crutch” that solves some of the past issues I have had with mounts. This style mount is new to me but maybe others are already using something similar.

This build started by cutting wood rather than drawing plans. And I was limited by the materials in my shop. I was in a hurry... As I start to design the nose for my new airplane, purpose built for electric and not constrained to the materials in my shop or the SV-11 dimensions, I have found several ways to improve the mount. That said this mount has been working well.

It might be hard to tell what's going on with the battery retainer. It is captured by the firewall and secured with two 4-40s in the back. The aluminum spacers are used because the firewall is set back to accommodate 15mm and 20mm length motors. Motor pictured is a 3515.

Mike

Offline jfv

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Re: Electric Crutch
« Reply #1 on: August 18, 2022, 12:23:57 PM »
Very simple.  What's your experience with rear mount re: motor bearings?
Jim Vigani

Offline John Rist

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Re: Electric Crutch
« Reply #2 on: August 18, 2022, 01:04:37 PM »
My biggest complaint with rear mount is that if you want to try a different motor it has to be the same length. Shorter you can add a shim behind. Longer doesn't work.   D>K  Having said that you mount looks solid. Great work!
John Rist
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Offline Brent Williams

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Re: Electric Crutch
« Reply #3 on: August 18, 2022, 03:07:26 PM »
Nice work Mike.

I'm using Paul Walker's method* for the motor mount on my latest projects. 
It is made from 3/8" balsa, faced with 1/32" plywood.  Maple dowels are inset at the motor mounting points. 
The 4-40 mounting bolts on the X-mount are easily accessible from the rear.  The blind nuts are on the front.
This makes a lightweight, rigid mounting platform with plenty of air pass-through.  At 7/16" total thickness, it should also make a very strong F1 to strengthen the nose.
 
This is the over size blank that will be further trimmed and fitted into the airframe.
 

* https://stunthanger.com/smf/open-forum/throug-the-firewall-moror-mounts-revisited/#msg552430
« Last Edit: August 18, 2022, 09:23:23 PM by Brent Williams »
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Offline Mike Palko

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Re: Electric Crutch
« Reply #4 on: August 18, 2022, 04:31:17 PM »
Jim,

I don’t have a lot of time on rear mounted motors but others have been successful. Some of it comes down to bearing size and quality. I’d rather replace bearings than a broken motor mount.

John,

For this size airplane motor sizes have been for the most part standardized. My mount accommodates both sizes. I had the same concern.

Brent,

Thanks for sharing. Paul’s mount has obviously been working.

I was considering a “through the mount” style on my next version. You might have noticed the two small holes just outside the nose ring with the allen driver sticking out. That is my access point for the two top motor bolts because the spinner on the SV-11 was to small to allow clearance from the front. The rear access would fix that. So would a slightly larger spinner.

Mike

Offline Mike Alimov

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Re: Electric Crutch
« Reply #5 on: August 18, 2022, 06:08:53 PM »
Mike, what did it take to separate the original engine mounts from the fuselage sides? Heat?

Offline Mike Palko

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Re: Electric Crutch
« Reply #6 on: August 18, 2022, 06:45:51 PM »
This ARF is old. A friend who moved and didn’t have room for it gave it to me. He removed the beams and converted to electric many years ago. I gutted the nose so I could mount a more modern power system and develop a new mount. The older ARFs had what looked like a hot glue type of adhesive. It was softer than epoxy whatever it was. Someone with more knowledge of the Brodak offerings might know. I think heat would be a good place to start.

FYI, the plywood doublers did delaminate a bit when my friend removed the beams.

Mike

Offline Brent Williams

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Re: Electric Crutch
« Reply #7 on: August 22, 2022, 02:22:02 PM »
As a follow up, here are a few progress pics showing the Walker style pass-through motor mount as installed in the new nose on the Sultan. 
Still more carving and work to do, but it's coming along really nicely *.  * (With much gratitude to Roger Kramar, this work is getting done!)
Top hatch and tons of room with easy access to everything. 
« Last Edit: August 22, 2022, 10:37:29 PM by Brent Williams »
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Offline Mike Palko

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Re: Electric Crutch
« Reply #8 on: August 22, 2022, 07:39:57 PM »
Looking good Brent. Please post pictures of the battery mount when complete.

Mike

Offline John McFayden

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Re: Electric Crutch
« Reply #9 on: August 23, 2022, 06:57:48 PM »
Brent, are the fuselage sides in the nose area lined with 1/32 or 1/16 plywood?

Offline Brent Williams

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Re: Electric Crutch
« Reply #10 on: August 23, 2022, 08:21:47 PM »
Brent, are the fuselage sides in the nose area lined with 1/32 or 1/16 plywood?

1/64" plywood doublers laminated to light 3/16" balsa sides. 
« Last Edit: August 24, 2022, 12:04:19 AM by Brent Williams »
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Offline TDM

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Re: Electric Crutch
« Reply #11 on: August 24, 2022, 04:52:12 AM »
Mike I have had good success with front mounting my motors. I just use a 1/8 good quality multilayer hard plywood and some triangular stock to get it locked in place. For fuselage doublers I prefer 1/64 plywood. The motor will be heavier than the prop spinner combination but it balances somewhat and releases the pressure on bearings. Anywise bearings are not too expensive and can be replaced rather easily. I just did replaced my bearings on the old motor.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Paul Taylor

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Re: Electric Crutch
« Reply #12 on: August 25, 2022, 06:08:51 AM »
Nice work Mike!!! Very clean.


BA made the mistake of putting a CAD drawing of there rear mount on there web site. I was able to 3D print one in case I ever needed one. 😆
Paul
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Offline Mike Palko

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Re: Electric Crutch
« Reply #13 on: August 25, 2022, 07:48:09 AM »
Traian,

I’ve had success with front mounting motors since 2004. My reason for going to a rear mount is to gain some strength with hopefully no penalty (weight, cooling, bearing failure).

Thanks Paul. What does the 3D printed mount attach to? Is there any benefit to using it over the standard X mount?

Mike

Offline Paul Taylor

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Re: Electric Crutch
« Reply #14 on: August 25, 2022, 11:39:17 AM »

Thanks Paul. What does the 3D printed mount attach to? Is there any benefit to using it over the standard X mount?

Mike

Hey Mike
I have not used one yet. I just saw it and snag a copy.
My thought was if I ever converted a profile I could make Cheek cowls like we use on 1/2’a to bolt to. I guess you could also bolt it to a plywood former. They show them on inova8te’s site bolted to a firewall. 🤷‍♂️
Paul
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Offline Matt Brown

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Re: Electric Crutch
« Reply #15 on: December 18, 2022, 05:33:49 PM »
I’ve only recently (2018) come to CLPA. Before that I’d been very much into RC 3D profiles. One of the things we’d found was that longer can motors rear  mounted did not fare well in the violent maneuvers we put them through. It wasn’t so much the bearings but the total flexibility of the motors. During hard maneuvers the motor would flex enough that the can would get the magnets hitting the stator. Front mounting essentially eliminated this problem. I’m guessing that CLPA corners are very similar loads to the hard 3D maneuvers we did. Front mounts create more airframe structural considerations but the strain on the motor and bearings are greatly reduced.

Matt


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