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Engine Mount

Old 12-30-2003, 02:51 PM
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Default Engine Mount

Hello,
I need an engine mount for my SPAD airplane coming up. I went and bought a 6" x 10" Poly Cutting Board. Is this what everyone else is using. I know you guys use cutting boards, but I dont know which kinds. Also, will this melt under the heat of my .061 engine. I did a search for enigne mounts, but couldn't find anything on it. THanx -Patrick
Old 12-30-2003, 03:04 PM
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Default RE: Engine Mount

If you search under HDPE or poly cutting board you will find plenty of info.
Old 12-30-2003, 03:33 PM
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Default RE: Engine Mount

Thats odd...If i searched under cutting or board. All I got was a few threads about cutting coroplast, or building boards. -Patrick
Old 12-30-2003, 03:35 PM
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Default RE: Engine Mount

with a .061 engine the poly cutting boards would be a bit of an overkill cos they r like half an inch thick and very heavy. just use some 1/4 inch plywood for that engine and it will be strong enough.
Old 12-30-2003, 03:41 PM
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Default RE: Engine Mount

Use the poly board and if you think it is too heavy just swiss cheese it with a drill. That is what I have done with mine. You won't have a problem with it melting and they are very durable. I have done my share of cartwheels and have yet to break one. Check out the spadtothebone website for details on how to make one.
Old 12-30-2003, 07:25 PM
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Default RE: Engine Mount

I am just cutting out about a 2in x 2 in section and using that as the engine mount. I figure it will weigh about .5 oz. I am making a big slow flyer though....So, the extra oz wont really affect it to much, because this is just gonna be a nice slow flying airplane. Thanx -Patrick
Old 12-30-2003, 08:35 PM
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Default RE: Engine Mount

Be sure to leave about an extra 2" from the rear of the hole cut out for the engine to mount it to the fuselage of your plane. I would also opt to make the sides at least 1/2" thick from where the ears for the engine mount to the board. I have found in several instances that is where they like to break. As a matter of fact, when I landed my QHOR rather hard yesterday, my motor mount snapped right at the rear of the engine.

Next one will be a little wider.
Old 01-04-2004, 11:55 PM
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Default RE: Engine Mount

cutting board breaks to easy, use ply
Old 01-05-2004, 12:37 AM
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Default RE: Engine Mount

cutting board breaks to easy, use ply
This is a general statement that is not true. All cutting boards are not created equal. You must be selective, and get a "Poly" Cutting board, the best brand I've used is American Chef from Wal-Mart. Be carefull, if it doesn't say POLY on the lable it may be second generation (recycled) plastic and will be brittle and break easy...one brand to watch out for is fiberware. The poly engine mounts I've been using (I still have yet to break one) have taken a pounding many many many times over where Ply would never have held up, not to mention the fuel proof and self tapping screw aspect that poly has over ply. Believe me, if ply was better, I would be using it since it's actually as cheap and lighter, and a heck of a lot easier to cut out...however, it just can't take the abuse I give my 3D airplanes.
Old 01-05-2004, 05:02 PM
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Default RE: Engine Mount

A bit off topic, but funny, I have broken 3 of the American Chef Poly (from wal-Mart) mounts. If Tattoo is rough on his, them mine must suffer unmentionable torture before they break - and they always break at the back of the engine cut-out. I do admit that my SPA3D is subjected to extreme punishment as I am always trying something new and I just end up beating the crap out of the plane. Thank god for coro

I have considered trying to find looooong drill bits to drill a hole on both sides of the mount and then pound in a piece of music wire on both sides to try and keep the danged thing from breaking so often. I end up having to cut a new mount about every 2-3 weeks. Fortunately I bought several pieces of the Poly so I am good to go.

Maybe I am cutting mine differently (it's done exactly to the plans)? Maybe Tattoo isn't nearly as hard on his mounts as he may think (compared to the torture that mine are subjected too)

But I do have to agree with Tattoo, the poly mount is probably easier to work with in regards to the material keeping a good grip on the mounting screws over plywood.

Just a thought,
Old 01-05-2004, 05:50 PM
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Default RE: Engine Mount

I have never broken a piece of HDPE (poly) motor mount or firewall. Stripped plenty of scews out of it, but I haven't broke one yet. A Plywood firewall or engine mount wont make it one trip to the field for me. The ply always seems to split for me. On the "lighter side", the ply typically weighs less.

Now you've got oppions from both sides of the issue. You'll just have to try both and see which one works the best for you. This is often the case, what works great for me, doesn't work for someone else and vice versa.

cc
Old 01-05-2004, 06:49 PM
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Default RE: Engine Mount

The only poly mtr mount I have ever broken was the one with the servo cutout. I quit doing the servo cutout. thudriver
Old 01-05-2004, 07:58 PM
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Default RE: Engine Mount

Mine are sort of diamond shaped, wide at the back of the motor mount,tapered narrower towards the front, tapered towards the back. havn't broken one yet, cartwheels and all. Worked so well, put one on my Pizza box too, as well as an aluminum channel.
Old 01-05-2004, 10:27 PM
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Default RE: Engine Mount

maiden flight dead stick in a crosswind, fell about 20', broke poly but not prop (first prop I didn't break) hehe
Old 01-06-2004, 02:00 AM
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Default RE: Engine Mount

When you cut the poly boards, look at the cross section of the cut area. On the lousy boards, you can see some form of bubbling in the middle. DONT use that stuff, I used it recently thinking it would be allright, and found that it gives way too easily (was in a Spaggi) after the second landing we found that it had cracked.
Old 01-08-2004, 08:17 PM
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Default RE: Engine Mount

can you use a walmart cutting board on guter pipe for a engine mount
Old 01-08-2004, 09:36 PM
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Default RE: Engine Mount

ya
Old 01-18-2004, 03:59 AM
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Default RE: Engine Mount

I have been drilling my boards at the corners and cutting only up to the hole, leaving it rounded in the corners. In steel fabrication, cuts are never made on 90*s because it weakens the steel and provides a place for a crack to start. If you pay attention to structural steel, you'll see that it doesn't have sharp angled cuts, but curved cuts. I've broken one board and it broke because the landing gear twisted it. It was a very hard crash that took out my wing also.

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