Old 06-05-2011, 08:55 AM
Tired Old Man
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Location: Valley Springs, CA
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Default RE: DLE-111 first start... warranty used, but things are looking good.

The mount was and is just fine. In reality it's probabaly a lot better than what you would have had in a plane. The plane would probably had metal standoffs that would have allowed a lot of twisting force to be applied to them since they are unsupported, independant legs. Watch your video again, closely, and look at the twisting forces applied to the engine mounts. Now imagine that same force is applied to 4 independant spacers about 2" long and 1/2" in diameter and you'll quickly understand why I will not use aluminum stand off legs. They become a torque multiplier and are very hard on engine mounts and firewalls.

As for the engine, don't tear it down yet. Pull the spark plugs and turn the engine over. Do you feel any bumping or resistance at top and bottom dead center? If you do at top dead center it's possible the squish band was too small and the piston was bumping the top of the cylinder. One Chinese manufacturer is notorious for this. Not DLE of course. You also have the possibility of foreign material ingested by the engine, essentially creating a piston stop. If the engine had been lying around the bench, carb facing up with the plates open, something could have fallen into the engine by mistake. It's a straight shot to the reeds and they won't stop anything unless it's too large to pass through the openings.

Had the prop been dropped by you or someone else prior to your owning it? Could have had a hairline fracture you didn't see or know about. Those always blow apart. Could have been a simple wood grain separation, but the loose screws absolutely allowed the prop to wobble on the engine hub. This will always destroy a prop in a very short period of time. Screws too loose or tight, when used on an engine tuned so baldly it's experiencing detonation can eat the center out of a prop hub. Wood or carbon. I have several examples of that in the shop.

Over torquing prop screws with a wood prop compresses the hub. Equal torque is no longer possible with a compressed hub, so wobble is pesent to some extent. Screws want to "loosen up" all te time so efforts are made to re-tighten the screws, generating more hub compression. They really didn't loosen, the wood continued to compress under the overtorque. So a few cycles of tightening that wood prop and a longitudinal fracture appears across the prop hub and into the blades.

Had a "small" prop strike? Better look at that prop real close and try a few bending loads to seek out invisible splits. Remove the spinner and prop to inspect the hub too. Guess what happens if a split was there, you missed seeing it, and use the prop again? The video was a great example.

Bottom line on props is to inspect them before you install them, continue to inspect them periodically, and buy an inch pound torque wrench. Then use it every time you install a prop or check the screws. Check the screws frequently. It's not a one time on and forget deal.
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