Have a plastic spinner, doesn't seem like I can tighten the prop very good. The plastic spins when I go to tighten it. It goes on an airplane with a cowl so it is hard to hold the shaft to get it nice in tight. I do use a lock nut on it, so will that be good enough? Any suggestions appreciated.

It's kind of tricky, but if you hold the plastic backplate and the prop, you can usually get it to tighten without slipping. After a point, it will stop slipping altogether

Make sure your spinner back plate is reamed to fit your prop shaft. If not the spinner back plate will tighten against the prop shaft and not the thrust washer making it impossible to get tight enough.

My thought exactly.

if the back plate is slipping the prop isn't tight enough...you can hold a prop blade to tighten the nut down

Running a four stroke quickly will get you trained on tightening the prop They will back fire and spin even a properly tightened prop.

The plastic spinner back plates are a real problem when it comes to really tightening up the prop. I've mashed them quite flat to the point of not being able to get the cone on. I finally switched over the the Great Planes aluminum back plate with nylon cone.

http://www3.towerhobbies.com/cgi-bin...?&I=LXBMY0&P=7

I tighten my props with one hand. Position the back plate in relation to the blades and check that the spinner hole align with the screw holes in the back plate. With a new plastic prop, it is best if you use a leather glove here or you can cut your hand. I use a 6" cressent wrench but a correct size open end wrench would be better. Put the wrench on the nut so it has a spread to the prop about 10 to 15 degrees, what ever the nut position will allow. Grasp both the prop blade and the wrench and squeeze them together. Filp the wrench over on the nut, gaining another 15 degrees or so and squeeze again. Flip it again and squeeeze and repeat untill you have a dificult time gaining on the nut. Most four stroke have a lock nut, so do the same with it.

Don

I'll try this, thanks for the help.

Not sure what you mean, but the spinner back plate is flush against the prop shaft plate. This is a real ***** of a problem. BTW I am using a 4 stroke (Seito 125). Thanks for the help...

I had the very same problem with my Saito 100 and a plastic spinner back plate. The solution for me was to take some very course sand paper and rough the back of the prop up, sand from the center out in a straight line not a circle, and then clean all the oil of the prop and back plate. I must have spent an hour getting that prop to tighten! For what ever reason a Master Air Screw prop would not tighten, I had to use a APC. Make sure you use a good solvent to clean the mating surface of the prop and back plate after roughing up with the sand paper.

good rule of thumb is to only use plastic on a 60 sized 2 stroke or 91 4 stroke,,,and smaller

good rule of thumb is to only use plastic on a 60 sized 2 stroke or 91 4 stroke,,,and smaller

Did not see this in the 11 posts so will offer it to you. Making sure the prop is correctly sized was mentioned. That is important. If you should get the prop hole too big, simply wrap some masking tape around the shaft until all is snug. It works.

Now if you have a spinner backplate that turns on you, normally it is the alum. ones that do so, but this works for plastic also. Make a washer about an inch or so, no fancy stuff, just fold some 180-320 sandpaper (Wet/dry best) and cut a half moon. Then make a cut to fit the shaft. No problem if it isn't tidy. The washer fits between the thrust washer and the backplate. Face the grit against the backplate and tighten the prop. It works.

One other item to consider is that with so many different spinner mounting items, sometimes one can run out of nut threads about a 1/2 turn before the prop is tight. That can drive one nuts. Another prop washer usually fixes that problem.

Good luck.

I would highly reccommend you heed this gentlemans thoughts. All Plastic spinners have no business on anything bigger and most expecially four strokes which suffer massive vibration in the plain of rotation which is the chief reason they try to constantly throw props and spinners all over the pits.

You have purchased a nice engine and now you want to use cheap and dangerous accessories.

Big four stroke can use plastics safely if you only use the aluminum backplate type with a capture ring. CB makes these as well as Great Planes but they are around eight bucks or so and not the cheapies.

If you use plastic back plate types in order to stop the slipping you have tightened so tight that now you have distorted the plastic and preloaded it for an explosion frequently right there in the pits.

Here is a couple of photos of a CB with alum capture ring backplate and thick plastic cone. The other is a TrueTurn all aluminum Both have sufficient knurling (especially the True Turn) and thickness of the backplate that they will properly tighten.

I would use nothing on that engine unless it had a proper aluminum backplate and it was a capture ring type.


John

Finally just taped the included backplate and using the plastic nose cone works great. Not trying to be cheap, just hard to find a proper fitting set-up for the 125 in my local area. Thanks for all the help.

One ? by half moon the sand paper what do you mean.

It is like cutting paper dolls, you fold the paper in half and cut the shape once along the fold, unfold and you have 2 of the same shape. If you fold the sand paper in half and then cut half a circle then when you unfold it you will have a complete circle. I hope that helped.

Rob

good rule of thumb...throw the spinners away.