sc1449

I Have a Saito 82 and I am using a Great Planes Aluminum Spinner and back plate. The engine is new, less than 30 min. of flight. I am changing props but I can not get the prop to tighten. After close examination it seems that the drive flange on the engine and the spinners back plate are somewhat deformed. They do not mesh together. It looks like I have tightend the previous prop with out mateing the two propperly. Do you know of a fix for this without buying new parts?

The Ghost

If the spinner backplate is bent it will have to be replaced. When fitting spinners always check the backplate is drilled to fit the crank.

Cheers.

SST

My Feedback: (2)

Are the prop hubs the same thickness? You may just be running out of threads, and need another washer under the propnut.

Scar

My Feedback: (3)

I read perhaps more than you are saying, into this post, so I'm going to ask a couple questions.

1. Is the prop coming off, when your engine reaches top speed? If so... you probably have the mixture too lean. Try opening the main mixture screw. If the prop comes off at low speed, as you increase throttle, try opening the low end mixture screw.
2. Is the spinner backplate out of plane with the prop hub, or are you saying it is not concentric with the prop shaft? Unless it is bent, I can't feature how it would become out of plane. However, if it is not concentric with the shaft, you may have omitted the centering shim, a little ring that comes in the package.

At least, that's my reaction to what you wrote. More information would help, and pictures are a definite benefit!

Best wishes,
Dave Olson

Stick Jammer

Not sure what you mean by deformed. The drive hub on the engine is aluminum and so is the back plate. Being the same metal it's difficult for one to deform the other to the point of needing new parts. The initial tightening usually leaves a somewhat "new" pattern on the rear of the backplate where the drive hub has dug in slightly. Mating them for the first time usually isn't necessary. After that you can "feel" when the two are meshed so to speak. Is the problem that the drive hub is just not "biting" into the backplate when you try to tighten the prop?

daveopam

My Feedback: (9)

I have had this problem with APC props before. If I understand what you are saying. When you try to tighten the prop nut the prop slips on the back plate and wont stay in place. I mentioned APC props because they are rarely flat on the back. I always sand them flat before balancing and this cures that problem.
I don't follow what is dammaged from your description.

David

bentgear

sc1449, let me add to the above, are you using a double lock nut? Did the backplate spin on the shaft causing the damage?

Ed M.

Steve Collins

My Feedback: (8)

To solve your slipping problem cut small "donuts" from sandpaper, something like 180 grit, and place these between the surfaces that are slipping. You might need 2 donuts, placed back-to-back, on each surface that is slipping. Usually there is slipping between the thrust washer and the backplate. Try there first.

This has solved numerous similar problems for me. Sounds too simple but it really works.