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HELP! With rear carb engine mount

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HELP! With rear carb engine mount

Old 01-17-2002, 02:26 AM
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Default HELP! With rear carb engine mount

I'm building a Lanier 35% Giles with a ZDZ 80 on the nose. The motor box sides are integrated into the airframe. I needed to angle the bottom of the box to clear the muffler. I cut a hole in the firewall to accomodate the carb and (after expoxying in place) pinned it to the sides with dowels. Everything is great except for the top. I was going to screw the top of the box down with wood screws to make an airtight box to quiet the engine. I don't know if this will be strong enough. What do you guys think? Here's a pic to better illustrate:
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Old 01-17-2002, 03:02 AM
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Default HELP! With rear carb engine mount

Epoxy, or glass in the top. Also make sure that the box attachment to the firewall is really solid. Again it would be better to epoxy and glass reinforce the box to the firewall. Vibration can really loosen things if you are not careful. Make sure you coat the wood with a suitable fuelproofing agent.
Mike
Old 01-17-2002, 01:42 PM
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Default HELP! With rear carb engine mount

How is the carb breathing?
Old 01-17-2002, 02:20 PM
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Default HELP! With rear carb engine mount

All the top piece does is help prevent the engine box from shifting side to side from vibration... I would install some blocks that could carry the load. Be sure and attach the blocks with epoxy and screws and then I'd use brass threaded inserts or blind nuts and loctite to secure the lid. I have done this on a few planes with no problems... The blocks that are against the motor box sides at the bulkhead were ran back into the fuse about an 3/4" and the ones in front were attached to firewall and motor box.
Old 01-17-2002, 03:49 PM
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Default Breathing

Originally posted by aerobat
How is the carb breathing?
The intention is to have the carb breathe through the airframe. If the box is airtight (except for the rear which opens to the airframe) it essentially will use the inside of the fuse as a giant muffler. This also gets cooler air to the carb, as it's not breathing from the engine compartment.

I like the block idea. I think I will fashion some corner braces out of 1/2" ply and epoxy them in place. Thanx for the help!

-Aaron
Old 01-17-2002, 04:01 PM
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Default Breathing

I also run a ZDZ80 single, and I can tell you that the carb soaks the inside of the motor box with fuel - you may want to make sure this isn't a problem with the carb throat open to the fuse. Also I assume you have the fuse vented somewhere.

Mark
Old 01-18-2002, 12:13 AM
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Default HELP! With rear carb engine mount

Like Michael says,all the top does is keep it from shiffting.I would open up the top of the box more & make sure your getting enough air & just epoxy it on.I would not worry about the noise from the carb.The Pitts muffler & prop make alot more noise than the carb. Do the blocks or use 3/4" cove molding(Menards) or aluminum angle to beef up the side to firewall. I've set up an 80 single before & I am doing a couple now...Yes, it will be strong enough.
Old 01-18-2002, 12:26 AM
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Default HELP! With rear carb engine mount

I just completed a Hangar 9 Cap with a ZDZ-80 and I made a new box top that attaches with 8 4-40 allen bolts and blind nuts. I put bass wood rails on the box sides, front, and rear with the blind nuts. The rails make a ledge inside the box for the top to sit on. There's also aluminum "L' extrusions that are bolted to the box front and sides in the 2 front corners. It's plenty rigid.

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