My Pulse XT 60 w/ Saito 100 has a 2 1/4" plastic spinner that does not want to tighten enough to hold the prop. I had to cut the spinner a lot in order for the 14x8 APC prop to fit but I would not think this would cause it to slip? I reamed both the prop and the spinner back plate to 8mm and the fit the shaft fine. I can tighten the prop nut VERY tight and it holds for a while but after a few flights I notice the prop has moved and is against the spinner. What could be the problem?

The only way I can think of having a loose prop is because the locknut came lose. Which can happen if the threads had oil on it and the prop was not balanced. The vibrations may have caused the nut to come loose. The spinner is just there to look nice and to be used with starters.
The prop is held by the Locknut and the lock plate, against the spinner plate which is pressed against the drive washer. Both the driver washer and the back of the spinner plate have groves and once fitted and tightly tightened, it is nearly impossible for the prop to come loose unless the locknut comes loose. Which seems to be the case.

Clean the shaft threads and the nut with the alcohol and try again.

Got pictures?

That sure sounds like you are using a single nut instead of a mandatory locking type double nut?

Big fourstrokes are notorious for that and only a collot type double nut arraingement will do. These engines are serious engines and not beginner types and they need to be used with serious accessories cheap plastic spinners espcially the type with plastic back plates are normally troublesome. I highly recomend something like a true turn for an engine of that caliber.

Here is an example of a true turn collet type double nutted adapter. Adapter refers to the fact this double nut has a threaded boss for a single 10-24 spinner bolt. The single bolt that hold the spinner on through a nose hole. This is the only type spinner I would ever recommend for that engine.

http://www.truturn.com/cgi-bin/store...3a&ppinc=adapt

I am using the double lock nut set-up. The prop nut is not coming loose, the prop is actually slipping against the spinner. When I remove the prop nut it is still very tight. I noticed the ridges in the spinner back plate where worn from the prop slipping, do you think a new spinner back plate would help? I hate to not use the same style spinner that came with the ARF because it looks so nice. I have tried to find a "better" spinner that would match the lines of the plane and have not had much luck. It may come down to function over form, but I have not gave up on using the correct spinner yet!

Cut some "washers" out of sandpaper. Glue two of them back to back so that you now have a sandpaper washer with grit on both sides. Use it between the two surfaces that no longer grip each other adequately. Size it to fit the shaft closely.

Well if you are determined you could try the oft reccommended cut out discs of sand paper or screen wire and slip em in here and there and that may even work for an extra flight or so But you will soon be back here Wanting to know why your cheezy cheap plastic back plate is slipping pretty soon. And be careful those can damage and smooth the knurling on your thrust washer compounding the problem every time they do slip.

This is a serious big engine with major torsional thumping in the plane of rotation as are a number of others big singles. Using cheezy entry level beginner type accessories can only go one way.

You are wrong about not being able to get most any style in a serious accessory. The differance is its going to cost and typically for that engine in about those sizes it will be about fifty bucks.

Go to this page and start here:

http://www.truturn.com/af.htm

You will be selecting Engine make and size - propellor make and size - Diameter and length and cone style amoung a wide variety. If you have trouble then call them they will walk you through everthing and even try various spinners on many give engines and props right there on the phone.

The ridges that are worn smooth can be refreshed. Sometimes the grooves are filled with what used to be the peaks. Scrape the junk out of the grooves. If the surface has been simply worn away and there really are grooves no more, then you can use a triangular file to scrape new grooves. Radial grooves are the only ones you should make. And not too deep. And the entire process isn't the 1st solution you should try. It's not a real good idea to weaken a backplate. Not a real risk, but if you over do the scoring it could become one.

That slippage can actually be a symptom of your 4stroke being run on the lean side. They have a tendency to backfire more when the needle setting is off somewhat. And they'll do it in the air and not always very obviously. Most people don't do as great a job setting 4stroke needles by ear as they think they can. And it's not too hard to be off enough to cause slightly rough running. It's just as hard to hear a 4stroke running slightly rough as it is to tell the rpm of one on the ground.

Thats a good idea! I actually had to lightly sand the mating surface of the APC prop to get it to hold enough to tighten the prop the first time I installed it. I think the problem stems from the fact that when I first tried to install the prop the spinner back plate had some oil residue on it which caused the prop to slip and wear the ridges down on the spinner back plate. I tried several times to get the prop to tighten but it would get to the point of almost being tight enough to hold and then slip, each time wearing the back plate ridges more and more. I then cleaned the back plate and prop with alcohol to remove the oil and lightly sanded the back of the prop to get it to grip the spinner back plate. It finally tighten enough, or so I thought! It amazes me that the Saito 100 puts out enough torque to cause it to slip. I am guessing I tighten the nut to around 40 foot pounds of torque, and it still slips.

This fellow tried the sandpaper trick. Of course made for an inexpensive engine for me after I find a new thrust washer.

The more you clamp down on a plastic backplate the more its going to deform and that is going to cause problems even out of round running. Many all plastic spinners do not have backplate capture rings and now When you really crank on the torque they become explosive.

Suggest if you use plastic at least get an aluminum backplate type and with a capture ring such as the CB and Associates sold by RJL or there is one Great planes type with alum backplate and capture ring.

Actually, since you're dealing with a 4stroke that already has shown you it's not running very smoothly, you really should lean very heavily toward getting a higher quality spinner, one with a metal backplate.

Chances are good that engine will defeat the sandpaper washers or the plastic backplate, one or the other.

from the description the prop and the spinner back plate doesn't have enough bite to grip each other as several posters have astutely pointed out.
don't put any sandpaper between the drive washer at(the engine) and a spinner back plate whatever type it is,alum.or plastic, the dust and grit can be harmfull in several ways beyond flattening the groves in the metal.

sandpaper discs between the back plate and prop is perfectly fine for slippage,which from your description is what is happening,also to crank that nut down tightly,part of the problem with plastic spinners is they squeeze out and get weak and can fly apart when tourqed down tightly,which on a 4st is important, on a saito100 the suggestions on getting a metal spinner is a good one, there much safer for 4st engines for a number of reasons, I don't use anything but metal spinners on all my 4st engines.

also something to consider is when you cut the slots in the spinner you might have thrown the spinner out of balance causing small amounts of vibration the plastic being much more flexable than metal allows the prop to slip no matter how tight you crank the nut down,just one guess since I havent seen your slotting job,but it doesn't take much.
its one reason why Tru-Turn,and Dave brown, ask what prop your using so they can slot your spinner accurately at the factory,if you get one from Tower the slots are over large to accept just about any size you may have.

also I have several, and like tru-turn spinners, but there the most expensive on the market and having to shell out 60-70+$ for a spinner is sometimes hard to swallow,there are several less expensive brands out there that offer many of the most popular shapes,such as Dave Brown products http://dbproducts.com/ which offer many popular types at half the price of T-T.
or another company that I have gotten spinners from is Racing Devil Hobbies http://www.racingdevil.com/product.php?category_id=105 which for the price are very nice quality and highly polished,they also come with a adaptor kit with the spinner included.

I had similar trouble on a Thunder Tiger F-91s 4-stroke when I tried using the plastic spinner that came with the ARF. I removed it and bolted the prop directly to the thrust washer while using a safety spinner nut on top of the double lock nuts at the end of the crank shaft.

Plastic backed spinners and 4-strokes just don't mix.

get rid of the plastic spinner...for me .60 and above gets aluminum

This is probably a stupid question but should I be using a double nut set-up on my 2 stroke engines? I have a O.S. 46fx and a TH .61 & .75. They all just have a single nut. Is this bad ju-ju?

Rufcut thats not a stupid question, its is a very astute one and the answer is no you do not have to double nut the small two strokes and they can also use the all plastic spinners. Using all plastic though the normal precautions must apply and their can be no contact betweeen blades and the slot and yes you can dremel trim the slots by hand.

Those engines are not subject to the same pounding in the plain of rotation most four strokes are.

I do as jetmech suggested and use the sixty size as my personal limit for the use of plastic spinners on two strokes and not at all on four strokes.

John

Thanks John,
I was worried I had been doing something stupid without knowing. It wouldn't be the first time[:@] I will say that I've never used the plastic spinners because they seem so flimsy. Besides, the aluminum spinners look a lot better IMO.

I've been using the Great Planes nylon cone with aluminum back plate for a few years now on my four strokes from 45 to 91. Not a hint of slipage with them. Like a couple of the guys said though the plastic back plates just will not hold up the the tightening required on the Four strokes.

Here is the ones' I'm talking about'
http://www3.towerhobbies.com/cgi-bin...?&I=LXBMY1&P=7

Don

Capture Ring

To illustrate that all important capture ring especially for a four stroke enginee I think you can see it in these photos. A machined or moulded grove around the perimeter of the backplate with a machined or moulded ridge that fits it in the spinner cone. This releves the centrifical loads from cone making this type much safer for four stroke use. The bottom pic is a typical quality alum spinner and the top is a CB plastic which along with the the Great Plains type that Campgems linked above are the only two plastics I am aware of with a alum backplate and a capture ring.

The plastic spinner on four stroke experience varies from person to person.

My brother built a Super Sportster 60 with Magnum 91 four stroke, and uses a GP or Dubro plastic spinner. He has at least 100 flights on the plane with zero spinner issues.

Other people report various issues. Other than trying various plastic spinners, until you find one that works, I guess I'd lean toward getting an aluminum one.

I agree with Carrellh. I've ran plastic spinners on 4 strokes with no problems at all. I have a plastic Dubro spinner on my Hog Bip with an OS 91 on it. When I reviewed the World Models Super Chipmunk I used the stock plastic spinner that came with the plane on a Saito 100 and didn't have any issues at all with it.

Ken