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changing motor mounts

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Old 07-04-2013, 08:48 AM
  #1
no_spamola
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Default changing motor mounts

Hi All
Does anyone know of a "work smarter not harder" methodof changing glow engine motor mounts? The current spacing of the motor mount on a hand-me-down Kadet is too narrow and the engine can't fit between them. Trying to minimize the amount of work, I tried a GP adjustable mount, but the firewall mounting holes didn't line up with any positionof the adjustable mount. Another option would to createa new firewall, set it up for the current engine, then glue or screw the new firewall directly to the original firewall. That would be the easiest and straight forward approach. The one I am least incline to do, would be to knock out the t-nuts from the old mounting holes, re-drill to the spacing of the new engine, then somehow fish the t-nuts thru the fuse to the front which can be a pain.

Any ideas?
thanks
John
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Old 07-04-2013, 09:33 AM
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Top_Gunn
 
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Default RE: changing motor mounts

I just changed the engine on an old plane from an OS .60 to an OS 55AX. Since the .55AX is considerably shorter and needed to be moved forward as well as getting a smaller mount, I just made a new additional firewall and bolted it to the old one. Worked fine. The engine mount is bolted to the new firewall. I did have to remove a couple of the blind nuts from the old firewall because of spacing considerations.
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Old 07-04-2013, 11:21 AM
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big max 1935
 
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Default RE: changing motor mounts

I plug the old holes in the firewall. Drill new ones for the mount you need & install the threaded inserts that Sig & I think Du-bro sell.They come in several sizes & have held my engines with no problem. Max H.
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Old 07-04-2013, 11:28 AM
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GREG DOE
 
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Default RE: changing motor mounts

John, Getting the T nuts in from the back side doesn't have to be that difficult. Take a 1/4" stick of balsa or spruce, and glue the T nut on it with CA glue. Be careful not to get glue on the threads. Poke the stick, with the nut on it, into the fuel tank bay area from the radio compartment under the wing. You might want to do this in two stages. Stage one: secure the nuts individually. Stage two: install the new motor mount. Another variation of this trick is to carve, or sand down the end of the 1/4" stick to a round stub that can be inserted in to the T nut. If my explanation doesn't make sense, think of a pencil with the T nut on the point of the pencil lead. Good luck, Greg
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Old 07-04-2013, 07:21 PM
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52larry52
 
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Default RE: changing motor mounts

Whatever you do, remember there is a fuel tank back there somewhere behind the firewall. Don't drill holes in it or leave the new mounting screws so long that they poke holes in it!
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Old 07-05-2013, 08:05 AM
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Default RE: changing motor mounts

Plug the old holes drill new ones, easy job. To install new blind nuts I drill a hole into the end ofa cut off threaded rod or boltof the correct diameter andsolderto a piece of wire and then thread the blindnut on the end.Fishthe wirethrough the holes in the firewall and then slide a nut down onto the threaded rod and tighten it up pulling the blind nut into the firewall.
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Old 07-06-2013, 07:14 AM
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no_spamola
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Default RE: changing motor mounts

Thank you for all the suggestions.
About 3 minutes after Ihit the post button, I thought, what a dumb question because a variation of Top Gunn's idea had just came to mind. The original mounting holes are used to hold the new smaller firewall on which the new engine mount is attached. How simple. The original firewall holes do not interfere with the holes in the new firewall. I do like the idea of threaded inserts. I have used them in woodworking projects but it did not dawn on me to use them here.
Thanks guys.
Cheers,
John
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Old 07-08-2013, 06:23 AM
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Default RE: changing motor mounts

The problem I see with threaded inserts is they can and do pull out. I would not use them for an engine mount. Blind nuts are used for a reason, Ihave used the inserts for landing gear and other less stressful areas though.
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Old 07-08-2013, 08:24 AM
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Default RE: changing motor mounts

When you are a know it al guy like me it is hard to admit that the idea Top Gun has is one of the coolest yet. Way to go TG, and thanks for the tip!
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