What I done with my OS 1.20 was pin the prop to the hub with 1/8 in role pins and a drop of lock tite on my higgley hub for secondary nature. Have not lost one since!

Sorry to hear about your loss. I'm surprised at it blowing the carb, But things do happen.

Enjoy,

Jim

Hey Denny,
It sounds like you are using a lock "washer" in place of the lock nut that is supposed to be used. The Saito engines I own all came with two nuts to hold the prop on. The one you install first has a countersunk area near the threads which faces forward. The lock nut has a small protrusion that fits into the countersunk area of the first nut when you screw it on. This design is what helps lock them together.

I have a bit of a question on that...when i put the nut on and the lock nut it leaves very few threads for the nut that holds the front of the spinner on..is that ok or is there a better way to do this? thanks in advance Kieth

My rule is if the tip of the shaft does not make it to the front edge of the nut, it's not safe to run.

I have not used that type spinner. No doubt someone can answer. With both of the proper lock nuts in place, how many full revolutions can you screw the spinner nut on? How many threads can you see before screwing it on?

You often can get what are called Jam Nuts at the hardware or bolt store. They are thinner than regular nuts.

Harry Higely makes some large diameter very thin nuts as has already been mentioned.

here is a link....

http://www2.towerhobbies.com/cgi-bin...?&I=LXL744&P=7

Enjoy,

Jim

In my best Welsh accent, "'ere is the 'arry 'igley":

Will that type of nut work with any type of spinner...i am not using a thread on...i am useing a true turn type( its not true turn brand) aluminum spinner. In other words i am gonna be replaceing the nut and lock nut that came with the engine 91 surpass o.s. and those interlock with each other .. here is a picture of most of it assembled the other is a picture of the last nut that is supposed to be put on and the front part of the spinner Kieth

If you have room, use the original nut that fits against the prop washer with this spinner adapter thread tight up against it.

And if there isn't enough room for the original nuts and the spinner adapter you can use the spinner adapter as the locking nut for the first nut.

Ken

I have used the nut that goes against the prop washer with a Dubro spinner nut (very tight) against it. From personal experience, I can tell you it won't hold against a backfire nearly as well as the factory locknut. Have had it go flying without the plane.

Flylow, nope, didnt use a lock washer, didnt see anything referring to a lock washer. I dont think using a lock washer would be a good idea.
For those of you that may not be familiar with what a locknut is. A locknut is a nut that has either been deformed to squeeze the threads or one that has a "plastic" insert that also squeezes tyhe threads of the adjoining fastner. We used these on full size aircraft (F-16s and F-4s in my experience) and I have never known a nut of this type coming off even when used on high vibration applications like the Vulcan Cannon, it spun fast enugh to spit out 6,000 rounds a minute, (100 a second) and never had one come loose.
I had a Harry Higley jam nut and a higley solid brass prop nut on mine when it let go the third time, it didnt help much. I had torqued it so tight I was afraid the threads might strip, it still spun off, thats when I decided to go the locknut way, never another problem.
A rule of thumb that we taught in full scale aircraft maintenance is a threaded fastner should engage, if possible, 1 1/2 times the diameter of the fastner. This is not always possible, but is the ideal formula for proper threaded faster engagment.
On the sucessful combination that has yet to fail to hold the prop on, on my OS 120, I used a 5/16-24 locknut, then since it was on a P-47, I wanted it to look somewhat like a full scale. I drilled partway (countersunk) into the back of the solid aluminum propnut so that all but approx 1/8 inch of the locknut was visible when they were both installed. This gave a somewhat scale appearance.
After all this I wondered why no manufacturer has made a solid aluminum or brass propnut that has the locking feature, that along with a higley jam nut would meet all the requirements and a somewhat scale appearance for a 4 stroke.
Denny

Reread my last post, I failed to include that I used loctite on the Higly propnut just for extra insurance.
Denny

The nut with a plastic insert sounds good to me. I would certainly give it a try. Thanks.

The plastic insert job will loosen but doesn't usually come completly off. The prop just windmills.

In addition to locknuts and Loctite, it is also a good idea to use a prop hole reamer and make sure the prop to shaft fit is loose enough to be able to push the prop on the engine shaft without having to thread it on. That way, if the prop nut loosens from a kickback, the prop will be able to freewheel on the shaft and won't force the prop nut completely off of the shaft.
If you have to turn the prop to get it on the engine shaft, it will force even locknuts off of the shaft when the engine kicks back.

Just thought of another issue that might be of interest to some. The last 2 to 3 threads on a bolt are not always the same diameter as the rest of the bolt, the threads taper at the end and do not grip as well as the rest of the bolt/propshaft. This feature allows the fastner to start threading more easily
Denny

http://www2.towerhobbies.com/cgi-bin...?&I=LXB943&P=V

I will be using the above adapter for a Dave Brown Spinner going on a Saito 100. It is a one nut design, after reading this post I am now having second thoughts on how safe the design is. If I use one of the original nut as the first nut, I don't have enough room for the spinner adapter. However if I use the locknut that came with the engine I have little but enough thread to screw-in the adapter.

Any recommendations please, before I fire this baby up....

Added links to adapter.....

http://www.dbproducts.com/

In general, three threads are enough for the 3rd adapter nut that accepts the center bolt to hold on spinners such as Tur-truns. I.E., if the nut threads on with three revolutions, it will be fine. My 160DZ 4-stroke is set this way. 500+ flights, no prop ejections, spinner stays put, and it probably kicks harder than any other 4S. But please read this carefully, the two jamb nuts are fully on the shaft. I'm only talking about the third nut which only holds the spinner and is not critical for securing the prop to the thrust washer/backplate.

I've had some setups where there just wasn't enough crank to get everything on. Often you can play "games" with washer thickness, nut sets, etc. such that you can get a safe jamb nut setup and still have enough threads for the third adapter nut.

Cheers.