Kevlar

My Feedback: (47)

I was flying this weekend and my OS 91 FS backfired with the starter on the nose, but luckily had not fully spooled up. The prop hit me in the gutt (no injuries, just a good scare) and I lost the two lock down nuts. In a pinch, I thought about using locknuts - you know the ones with built-in nylon washer - but safety and the thought of that prop told me otherwise.

Would that have worked, one Nylon locknut as opposed to the compression nut system. What about two regular nuts?

rajul

My Feedback: (58)

I took the same route as you when I first started with four strokes i.e. using spinner nuts and I had a similar experience. I use Truturn spinners with double jam lock nuts exclusively with all my Saitos primarily for safety reason (they don't loosen easily in the event of a backfire). Using an electric starter makes starting a breeze and safer too. Turn the prop cw until it hits compression, then apply the starter. In this way, especially for larger engines, the momentum will be sufficient to rotate the engine through the compression stroke. Also, tune your engine well with a tachometer, and don't flood the engine before you start, as these may cause a backfire. Hope this helps

scratchonly

I use heavy hubs and TIGHTEN THEM. I have had the prop slip while starting, but they don't come loose. Also I notice many pilots advance the throttle somewhat to start. A properly adjusted engine should start at dead idle. I fly only 4S.

MinnFlyer

My Feedback: (4)

Yes and no.

Using that method will probably result in more loose props than with the original system, however, a nut with a nylon insert will prevent a loose prop from coming off.

While both systems are called "Lock Nuts" they are very different in nature.

The 2-nut system is designed not to break loose - but once it's loose, it can easily unscrew

The nylon insert type can easily break loose under to load of a piston engine, but once it's loose, it will stay on the shaft.

If you really want to go safety crazy, you could use the 2-nut system, then if there's still room on the shaft, add a nylon-type lock nut.

Another method would be to start with a regular nut, followed by a nylon insert nut that is tightened against the first nut (in this method the second nut is called a Jam Nut)

Kevlar

My Feedback: (47)

Now that I think about it - I was using the starter because I put a small cut in my finger from flipping the engine. Usually starts no problem, but I may have flooded it and forgot to dull the APC prop. Those suckers are sharp!

So with the starter running as normal and as we no lefty-loosey, the engine burped enough to 'maybe' loosen the nuts, and the pressure from the starter helped to finish the job - as the engine spooled up? No cone, just the prop, washer, and a wee bit of nutts!

I'm placing a Tower order so will get a replacement set for the O.S., but I like your last idea Minn - regular nut w/nylon jam.

I wonder how the heat of the engine would impact the nylon washer if at all.....