pulley bolts

Does anybody have a good lower pulley bolt sourced for a 3/8-24 BAE screw application? I've been using the NAS 12pt RCD bolt torqued to 45 ft lbs with red loctite and safety wire. The bolts are not staying tight. I use a huge 11mm pulley so there is some abnormal load with my setup.

Thanks
Mike

 

washer

yes I have the washer to fit the big radius of the NAS bolt. They have a nice fit and shank without threads but the tensile strength is not impressive.

 

Mike C, you are referring to this, right?

 

That's what you need.

 

Part #/

What is the part number for that, can't find it on RBS site. TIA

 

On the RCD site.

http://rcdengineering.com/search/blower-drives/listall?cat=15&start=1517&end=1570

 

What all do you do when installing these bolts Mike C......torque number, loctite, safety wire?

Thanks!

Joad Donnelly

 

How do bolts come loose when they are safety wired?

 

The safety wire was stretched to the point of being able to play a G chord on it after a weekend of racing. lol Seriously though, it was tight enough that the .032 safety wire had some serious tension on it. So even though the bolts weren't technically loose they had obviously backed off some.

 

Thanks Mike

 

We've talked about going to 7/16. Are there parts available for this or just modify the existing stuff?

 

You might want to review your safety wiring method, the tensile strength of safety wire is quite a bit higher than the bolt and the wire is to be set under force against the bolt in a tightening way.

 

As has been said...Unless you are running the ring the bolts aren't backing out and the safety wire isn't stretching. The larger diameter pulley is oscillating and the softer pulley material is being cut away or squished so-to-speak by the bolts as the pulley moves on the hub.

 

I worked in aircraft quality for close to 20 years so I've seen a few safety wires. I didn't say the wire was stretching, I said the bolts were backing off and pulling the wire tight. I seriously doubt there is anyone who can install safety wire in such a way that there is enough load in the tightening direction that zero movement is allowed in the reverse direction if one were to apply load in the reverse direction with say a wrench.

After racing this past weekend it appears the bolt are backing off enough before the safety wire stops any further movement that we are losing approximately 10 ft. lbs of torque. If you you have ever paid attention to the amount of movement that is generally required to change the torque applied to a decent quality 3/8 dia. bolt in most applications you will know that a 10 ft. lb change is very little actual rotation.

Joad Donnelly

 

Are you saying the ring is causing the bolts to back out? I don't think that's what you meant but that's kind of the way it comes across when I first read your post. And like I said in my previous reply, I never said the safety wire is stretching.

I don't think we are experiencing the pulley materiel being cut away or squished as you stated, there has never been any signs of this when these parts are disassembled. At least I would think it would be pretty easily to see with the finish that the pulley has.

Joad Donnelly

 

Not wanting to start an argument but you did state that the safety wire was stretching:

Also, I was taught when safety wiring that you are supposed to "pre-load" the wire and not leave any slack, that is why I questioned your safety wiring method. The whole purpose of safety wire is to prevent the bolt from turning, if your bolts are turning, even the slightest amount, then your safety wiring is incorrect.

I too worked in aircraft quality, for over 25 years, and also did a lot safety wiring in the military and a loose wire, i.e. not taut, was automatically rejected and had to be redone.