Thorp Air Command - T18.net

I would appreciate some input on the correct material for hanging and engine on a dynafocal ring mount. I have read a few posts on some other message boards and would like info from the Thorp community. Specifically I am questioning the length of the spacer rod/tube that came with my new set of Lord mounts. It measures 58/32" in length. The Lord biscuits are each 27/32". My dynafocal mount cup is 29/32" thick. I have read that the rod/tube is to prevent over compression of the biscuits. If that is the case then summing up the parts I get an interior distance of (27/32 + 29/32 + 27/32 = 84/32") The rod being only 58/32" would allow a compression of nearly half of both biscuits. The next puzzle is HOW to compress the biscuits this much; the length would be 26/32" yet the thread length on an AN7- bolt is only 21/32".
Is the rod spacer the incorrect length? Are the biscuits not to be snugged tight to the spacer rod? Is my dynafocal cup too thick? Am I using the incorrect Lord set? What length bolt is correct? Do I fabricate a new longer spacer?

Terry Adams
N51079 Lyc 0-320 E2D Bendix injection
KSCK

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[b]Terry[/b]

I believe that the plans show the proper length of the spacer.

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Bob Highley
N711SH
SN 835
KLAL

Related topic: The oil pan of my engine is up against one arm of the engine mount. As the engine vibrates, the two will rub, not good. What's the solution?
Engine is a Superior IO360B1A2, dynafocal engine mount came from Cubes. The mount rubber pieces are Spruce Part# 08-03500, $449, for EAB only.
I tightened all four of the 7/16 engine mount bolts to about 475 inch-pounds, the mid value in the specified range of 450 to 500.
Are washers needed for spacing? Where?

I have not seen any sump rub on our mount. Not sure why it would. Can you email me a picture?
Cubes

Here's your picture, such as it is. The arrows show the point of contact. Right now, there is about a 3/16" gap where the contact normally occurs. That's because I have removed the two lower engine mount bolts. When I insert the bolts and tighten them, the sump is pulled hard against the arm of the engine mount.

What to do? The only thing I can think of is to put a couple of washers between the lower, forward rubber buttons and the engine. That will push the bottom of the engine away from the engine mount. It will also point the engine up. The width of two washers is 1/8", and the distance between the upper engine mount ring and the lower ring is 11". So, the engine would be pointed up by arctan((1/8)/11) = 0.65 degrees. I'm assuming that pointing the engine up by less than a degree won't make the plane fall out of the sky.

I'm open to suggestions for an alternate approach.

I’m baffled. The engine is canted down to provide over-the- nose visibility. And for no other reason. So, removing some of that downward cant will not hurt anything as longer as the cowl fits. I know you cannot put washers on all four mounts because you will then not be able to get the four mounting bolts installed.
We have sent out dozens of these mounts with no issues, so I do not understand why this mount/sump is having any contact. I’ve contacted the welder.
In the mean time, you can install washers as long as the cowl will fit.
Cubes

Are you sure the tubes inside the mounts are the correct length? And are you sure all of the mount parts are installed correctly?
The bonded steel washers are away from the engine mount and the tube should contact the inside of the bonded steel washers.
Just making sure.
Cubes

I'm baffled as well. Surprised, and dismayed, that I'm blessed with being unique with this problem. I thought the Superior engine was just a copy of the equivalent Lycoming, so Lycomings should show the same problem. But I don't think the problem is with your engine mount, it's unique to this engine.

The spacer inside the rubber buttons is what came with the parts. The buttons are mounted like you say, with the metal faces away from the engine mount ring. I haven't seen any information that would indicate that the spacers aren't the correct length.

Ah! You nailed it. I read right past the Superior in your post. They are not the same. Especially the cold air induction sump. That sump, bolted to my Lycoming, will give the same result.
Are your cowling pieces all mounted?
Cubes

Cowling pieces have all been set. Tilting the engine up will likely cause some fit trouble. I didn't notice the sump/mount rub until after I had set all the cowling.

Why do you ask?

This engine came off a wrecked RV7. The baffles and servo came with the engine, and I have had to do lots of work to get the baffles and servo to fit within the Thorp cowling, which is obviously much tighter than the RV cowling.

With two washers (1/8" total width) in place between the lower rubber buttons and the engine, there is about a 1/8" gap between the oil sump and the engine mount. I'll keep a close eye there to look for rubbing.

That’s not much. Mounts tend to sag over time. Does the cowl still fit?
Cubes

By tipping the engine up like that, the front of the engine is raised so much that the bottom cowl section is pulled up to the point that it rubs against the fuel servo. So, the short answer to your question is No, the cowl doesn't still fit.

Is it possible to modify the engine mount? If that one brace could be moved aft by maybe 1/2", the problem would go away.

Yes. I suggest you do that locally. But if needed, my welder said he would do it.
Cubes