JoeAirPort

My Feedback: (41)

How much of the spinner bolt should be threaded into the prop shaft on a 50cc gas engine? The spinner is about 4 inches deep and the bolt is around 2.75 inches. I am thinking 1/4" inch minimum? Or should it be more like 1/2"?

Thanks

Antique

My Feedback: (4)

Old rule of thumb is twice the diameter of the bolt....

JoeAirPort

My Feedback: (41)

That makes sense to me. For my 10-32 bolt @ 0.19" dia, it ends up at 3/8" of thread.

Thanks

jak_kkaall

I have the aluminium spinner that came with the Great Planes 27% Cap 232. It's length is 10,5 cm and the bolt is 7,5cm. The bolt is a 5mm diameter and it is screwing into the prop shaft about 6-7mm only (the grey color). As I read of many broken bolts, I would like to keep this one because it has a 12,9 grade and I don't think that I will find in my area as hard as this one although I might find a longer one. Should I use this one because it's high grade or a longer and softer one?

a70eliminator

I would use it as is, you have more than edequate thread, it only needs to hold the spinner snug to the base, no much load to bare, just use locktite as it appears you already do see resdue on threads.

jak_kkaall

I will use the spinner's bolt then, after all it came like this so this is how it should be. They could have made it a bit longer though... I've searched and can't find longer than 5 cm only ones that are crap are longer. The residue is from locktite that I used to try the spinner. I'm in doubt about using locktite as opinions are 50-50 on "spinner bolt" threads that I've read. Some do not recommend it because of the many times that one has to check the prop bolts and disassemble the spinner, false torque needed, and maybe other reasons too. So I will put just a little or I will think and read more. locktite on prop bolts I understand that is a big no-no so I will not put any, just 2-3 lock washers on each prop bolt and check them often. Thanks!

irocbsa

My Feedback: (12)

Just use blue locktite, not red. That way it provides the security of a bolt that remains tight but does not require heat to remove.

jak_kkaall

Ok thanks. I only have red, but will buy blue one to. I badly assume they all require heat to loosen up.

pilotpete2

Locktite on a spinner bolt is not a good idea and is unnecessary.
I have never seen one come loose. Remember that the bolt should only be torqued as much as you can torque it with your fingers gripping (this it Tru-Turns recommended method) the short end of an "L" allen wrench. Old Locktite can result in the bolt not really being fully torqued, since it takes more torque input to overcome the Locktite. Over torquing the bolt can and will destroy the spinner.
Pete

Lone Star Charles

I have had a spinner come loose and separate from the plane in flight. It destroyed the spinner and nicked the prop such that I had to replace it as well. Since then, I have used blue loctite on the head of the bolt, not the threads. That way it does a good job of locking the bolt, but does not gum up the threads. I've had no failures since.

P.S. I had only the one failure before I started using blue Loctite.

a70eliminator

If you want more thread into the bolt add another washer to below, this may or not be possible on your set-up just a thought.

kmeyers

I just looked it up. 7.5 mm of engagement is recommended for Long 5mm screws with a pitch of 0.8mm. Your 6-7mm discription sounds close enough for me.
You left out what engine this is. For a Short screw the engagement length drops to 2.5mm just three threads (this is why I'm sure you will be fine).
I'm wondering if this screw is full threaded or has a long non-threaded portion?

jak_kkaall

More than half of its length is non threaded, is this good ? Does it give it more strength? The Engine is XYZ 53cc twin.