Decoop2

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Kinda new to gas and need thoughts on this motor mount set up.
DLE 55 on a Byron Ryan STA
I have beefed up the firewall to 1/2" thick and added 1" hardwood dowels where the standoffs mount. I placed the aluminum plate between the standoffs thinking it would be the same as building a box to mount to.
The legnth from the firewall to the mounting lugs on the motor is 5 7/8".
Question is will there be to much vibration that this set up will fail??

All Day Dan

My Feedback: (5)

Coop, you better build up a mounting box instead of those lengthy standoffs. What you have created there is a very long cantilever. With the piston and connecting rod moving perpendicular to the standoffs there is going to be an excessive amount of vibration. And I mean a lot. Dan.

Truckracer

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I've never been a fan of stacking standoffs. I would have built a box out from the firewall as far as possible then use shorter standoffs from the new firewall location to the engine.

Decoop2

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Thanks for the suggestions guys. I had a box built first and didn't like the looks of it, then after I built it up this way I started thinking about the vibration it might cause. I will go back with the box and 1 set of standoffs.

Truckracer

My Feedback: (19)

When I add a box to a firewall like that, I usually cut a square hole in the large firewall the size of the box. The box is then inserted into the hole and it even extends a bit behind the firewall. This gives gluing surface on both sides of the firewall plus additional area where triangle stock can be added. This produces a very strong and stiff structure.

Decoop2

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Good idea truckracer hadn't thought of that. Due to the shape of the firewall and the size of the box I will need do you think a box that will fit my firewall and a larger faceplate that will fit my motor mount would be ok? (The faceplate would be larger than the box where the standoffs will mount)
Reason I ask is the firewall bolts to the fuselage and I can't cover up the mounting bolts with the Motor box.
1/4" plywood heavy enough?

Truckracer

My Feedback: (19)

Wow, looking at the back side of your very narrow original firewall, that does present a problem! Just thinking out loud here, I'd probably make a box smaller than the standoff footprint from the engine then cap it with something like a 3/8" Birch ply firewall that I'll call the front firewall. I'd size the box so the standoff bolts would be outside the box and I'd probably use some aluminum angle between the front firewall and the box. The standoff bolts would go through the angle for additional support and the face of the angle that mates with the box would be attached with self tapping screws ... maybe #6 or so. Any preferred attachment method would work. The angle would also glue to the front firewall and the box and would extend from the top to the bottom of the front firewall and box junction. With the aluminum angles in place, a 1/4" Birch ply front firewall would probably be adequate.

I've also done similar mounts where I replace your rear standoffs with heavy wood blocks, usually one long block on each side that contains two stand off bolts. I then bolt through the existing firewall to the engine standoffs. I use heavy fender washers anywhere the standoffs contact wood and on the back side of the existing firewall. I don't think this would work in your case because the top engine standoffs are just too wide for the firewall but maybe the idea could be adapted some way to accomplish the task.

Not sure I helped much but maybe there is some idea here that can be adapted to that very narrow firewall.

Below are a couple of photos of the two block method I used to mount a new DLE 85 to an old Staudacher for testing. I can see ways this could be adapted to your situation.

Truckracer

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Added photos to previous post.

Decoop2

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I like the solid wood blocks. I think I could use that idea with the aluminum plate I made bolted to the solid blocks those could be epoxied and bolted to my original firewall that is now 3/8" thick.
What type of hardwood did you use?
Thoughts?

Truckracer

My Feedback: (19)

I think those blocks in the photos are hard yellow pine which is actually a bit soft for the purpose. I think Birch or Maple would be better. They were on top of previous blocks that were thick Birch Ply. That plane has had several engines on it over the years and the 85 was being tested before installation on a Ziroli warbird. The 85 ran very well so I was well pleased with the results.

Decoop2

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Thanks again for your help on this. Think I have a good plan. I will post pics when I get it put together and before I glue everything in place.

Truckracer

My Feedback: (19)

Good luck with your project. Its good to see people "building" projects.

Decoop2

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Ok take a look at this. I had some walnut 1 1/4" thick so I made the blocks out of that. 4 bolts go through from back of the firewall through the aluminum plate. I had to mount 2 of the standoffs inward slightly due to clearance but kept them as close to the solid blocks as I could. Nothing epoxied yet but will epoxy the blocks to the firewall. Didn't get pics of the back side of the firewall but I used heavy fender washers at the mounting points.

Truckracer

My Feedback: (19)

I think that will do the job! There's some weight in those blocks but you probably need the nose weight anyway on a Byron plane.

Decoop2

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Yeah I thought about drilling a 1 1/2' hole in them but didn't just for that reason I did router the ends that took a little off. They are all bolted up waiting for the epoxy to set up.
Thanks again for your help I've been in this hobby going on 40 years now and seems that every kit I build I learn something new.Almost ready for paint

All Day Dan

My Feedback: (5)

Coop, you will be better off if you epoxy those blocks to the firewall in addition to the screws. The long screws through them are still subject to flexing and movement because of the cantilever action. Dan.

spaceworm

[QUOTE=Decoop2;12161652]Ok take a look at this. I had some walnut .../QUOTE]

I could be very wrong, but I seem to remember that walnut is oily and can be hard to get a good glue bond. You might check on this. You might be better off with maple or birch than the walnut, or make a trial glue joint with the walnut. Good luck.

Decoop2

My Feedback: (1)

Thanks All Day Dan I epoxied the blocks to the firewall and also coated the bolts with epoxy before I ran them through the mounting blocks. (Hope I never need to remove them ha ha)
It all looks and feels extreamly solid.
One more question is there a problem with making a servo mount attached to the back of the firewall for my choke and throttle control.

Decoop2

My Feedback: (1)

Thanks for the thought spaceworm this walnut is probably more than 10 years old so should be pretty dried out. Unfortunately I have already glued it in but I have some scraps left over that I will test for bonding strength

Truckracer

My Feedback: (19)

I've used old mature Walnut for other (non-RC) projects and it held glue w/o any problems. I can't say the same for Redwood though as I've had some glues just peel right off that wood.