I went to start my engine today, threw on the electric starter, and the prop came loose! took off the spinner, wiped off the nut and spinner, and tightened everything again, and it came loose again! I've had this problem with both planes i have owned. Whenever i put a spinner on, the prop likes to come off. I've noticed the whole area around the prop gets fuel or grease on it. I'm guessing this is the problem. I washed everyhting off with rubbing alcohol, and am now waiting for it to dry up. I've never seen other people (Even beginners at my field) have this problem, yet it happens to me all the time. Any suggestions?

On the backplate there should be two little pegs that the prop should rest against so it dosent undo the nut when you whack the starter on, at least there were on the spinners i used to use before i discovered the domed nuts these are much much better with less vibration etc.

Wooden props are notorious for this, what type of prop are you using?

the fact that you have a lot of fuel around the spinner is a bit of a giveaway,you are flooding your engines to the point where you are getting hydraulic lock which is why the starter is undoing the nut-the engine can't turn over so the next thing in line is.

Thats what i was thinking bigchap, however, even when the prop turns over fairly easily, it still unscrews it. I'll work on it again tomorrow. It's not a wooden prop.

how is the prop driver keyed to the crank?

How are you applying the starter?

If you are jamming a spinning starter against the spinner the nut will come loose easily.

The proper way is to put the starter cone against the spinner and THEN press the starter switch.


Phil in MN[8D]

i just had a thought, i had a super tigre 45 which did it once,it was down to a split prop driver which you couldn't see until you tried to tighten it onto the tapered cone on the crank.

NO NO NO

EXACTLY the same thing happened to me: the spinners black plate, has 'teeth' these get warn away!!
TRUST ME< change the spinner and it will be fine. i now have a plastic spinner, but with a alu back plate,
degined to stop the prop comeing undone, made but Irvine Ltd.

i hope this helps ----- let me know

cheers
volkan

Actually, it's pretty common. I saw one come off the plane and lodge in the guy's forehead. The solution usually is to tighten down the prop nut more. Not flooding the engine helps, but if you can turn it over by hand, it's probably not flooded. If you're using one of those little 4-way wrenches it's hard to feel the right tightness. Get a box-end wrench. It'll be about 4" long, and you can bear down pretty good on it. The chances of stripping the threads are close to nil.

It is a common problem & there is a common solution. You simply make a couple of friction discs out of medium garnet paper & insert then between the backing plate & engine, & between the prop & backing plate.

Cut 4 discs of garnet paper slightly larger than the prop hub diameter & glue them back-to back to make a pair of double-sided friction discs. Punch out the shaft hole & install them. Magic!

Many of the suggestions are good ones. I would suggest a prop nut. I use them alone without a spinner. Dubro and Harry Higley are the 2 that come to mind. I myself use Higley nuts as often as possible. You could also use a prop nut under the spinner instead of the luck nut. You really can tighten a Higley nut down. Be careful and good luck.

Mark Shuman

Also before putting the starter roatate the prop clockwise all to the end of previous compression, and then apply starter this way the prop will not be at the compression and you will see that you will not put scratches on the spinner and starter will turn easier and you will have your spinner and prop in place.

I recommend getting a Prop Nutt.. They are easier to work with, they are easy to check if they are tight or not and take no time to put on and take-off when you break your prop. With the spinners, it is just another potential hidden problem that you may not notice until it is too late.....

I already do that cobra. I think my main problem is that when fuel gets on the bolt, it loosens up right away. I've bought another bolt ( for 3 bucks at Hobytown USA ), but it still does the same thing. I have a 4-way wrench, but for some reason, it doesnt fit around the prop nut, so i have just been using some pliars to get her on there tight. Before when i had this problem, i took the spinner off, and just started the engine by putting the starter on the prop and spinning it that way. It worked, but the guys at my club said i should use a spinner.

A question about the Dome nuts: Do you rest the starter on those? Wouldnt that just unscrew it? Hobbytown has them for 15$, so i dont want to get one and then have the same dumb problems.


Oh, by the way, i hate Hobbytown.

pliars won't do the job, you need to really thighten it.

for,
Again you have to tighten them so that they won't come loose when you apply the starters.

If you use Dubro a safety spinner nut, you can use a 1/8" music wire to tighten the nut, instead of a wrench. Wroks great.

if you are going to buy check Tower hobbies, they have spinner nuts for $5-7, it would be and with $4 express shippin it would be cheaper than hobbytown.

But your first thing to try should be a wrench instead of pliers.

No use in starting a new thread:

I ran the engine today, and the prop stayed on. I guess the fuel got it loose, and i also used a wrench this time.

Some odds and ends though, There were still some bubbles going from the needle to the carb. Occasionally it shut the engine down, but i set the needle so it stayed running. It ran pretty well today, so are a few bubbles in that tube normal? I assume there would be, but other than that, the engine ran great!

I'm also afraid to ask this but when i made the plane, the plans didnt call fow down/right thrust! How will this affect the plane?

The reason your prop didn't come off this time is because you used a wrench. You can not get the prop nut tight enough with a pair of pliers. (Unless they're channel locks or something very large.)

Air bubbles in the fuel line are not good, you shouldn't have any. Check for a pinhole in a fuel line somewhere between the tank and the carb (replace the line), or it could be an air leak around the needle valve.

No down thrust could result in the airplane climbing as you add throttle (instead of just speeding up), a lack of right thrust could cause the plane to pull to the left, and could be quite obvious as a problem during take off runs. If you haven't seen these problems, don't worry about it.
Dennis-