My tail pulley pin mod

[Bob O]

As much reading and searching as I've done in the past few weeks, it's still possible that I didn't see this somewhere, especially considering how long the Raptor has been out there. Someone please point out if this has already been done and/or tried.

If it hasn't, I'll call it the "Bob O pin mod".

If you guys have kept up with my X50B build and tail problems, then you know the problems I've had with the tail pulley retaining pin coming out. The first tail failure was on April 7, 2012, and this involved the factory metal tail case, and new style pulley and threaded pin.

The second failure was on April 25, 2012, which involved the stock plastic tail case, and old style pulley and pin. Here's the thread on it:

https://www.helifreak.com/showthread.php?t=403413

On May 6, 2012, I flew the stock tail with a flat spot ground in the retaining pin so the grub screw could lock into it rather than just grab the surface. This held fine for five flights.

On May 7, 2012, I modded the pin in a way that I've not seen before. Again, someone point out to me if this has already been done. Here are the details of what I did. I've flown two gallons (about 25 flights) with this mod and haven't had a failure. I inspected the pin after about five flights and found no signs of wear. Here are the pics:





The fit of the washout pin is perfect in that it's the same diameter as the stock pin. The length of the washout pin is also perfect, in that once the E-clip is in the groove, there is no play at all. It's almost like the washout pin was intended to be used on the tail pulley.

My only concern is that the pin is not hardened steel like the stock pin. Instead it appears to be aluminum. As I said, there are no signs of wear to the pin, and I'm not running with a grub screw or pin retaining screw. Initially I installed the screw but was afraid to tighten it too much against the aluminum. When I took it apart the first time, the grub screw had loosened and backed away from the pin. But since the pin is secured by the clip on one end and the head on the other, there was no failure. The original pin had some grooves in it from the grub screw, but nothing that damaged it.

So far the pin is holding up just fine. I'm going to try to get someone or some place to make this pin out of steel. If for nothing other than peace of mind.

I have to run my daughter to the doctor's office. Tell me what you guys think of this please.

DISCLAIMER:

If anyone chooses to run this mod based upon this post of mine, you acknowledge that neither this post nor the mod have been approved by Thunder Tiger. Also, you acknowledge that the washout pin is made of aluminum and not steel, and therefore might not be strong enough for use as a tail pulley retaining pin. Use of this mod by anyone is thereby done at his or her own risk. You also agree not to hold Bob O, HeliFreak, or Thunder Tiger responsible for any damage or injury as a result of utilizing this mod. Any damage or injury to any person or property will be the responsibility of the person who performed the mod to their heli.

[carlos]

Bob in all honesty in you linked thread you mentiond using loctite to hold a metal threaded pin into plastic. This is of couse a no no, Loctite is no good for plastics. Thick CA is the best for retaining metal screws into plastic.
I have heaps of flights on all four of my X50s and not a single failure, maybe all the problems you have had could have been avoided by using CA.
Hope your daughter is OK.
Photos not working so it is difficult to work out what you have done.

[Bob O]

Originally Posted by carlos

Bob in all honesty in you linked thread you mentiond using loctite to hold a metal threaded pin into plastic. SNIP

Hmmm, I'm viewing the pics just fine. I'll check into it.

As far as the linked thread, I mentioned using loctite but not between metal and plastic. As far as I know, the pulley, TR shaft, pin, and threads are all metal. I'm definitely not beyond making a mistake, so could you please point out where the plastic is in the parts that failed?

ADDED:

Here are the image links without the IMG tags. See if they work.

https://www.helifreak.com/attachment...1&d=1337796677

https://www.helifreak.com/attachment...1&d=1337796677

[carlos]

Thanks Bob pictures seem to be working for me now.
The mod you have done looks great but I am unsure why it needs to be done as I have been flying Raptors for 13 years and not had a tail failure like the one you are explaining. Although I have heard of others having problems.
If I can explain how I have fitted the grub screw and pin for the STD type one show above.

Fit the pin and using blue loctite apply it to the grub screw both on the end and on the thread.
Now fit the grub screw and do it up tight but not with a normal allen key as they are generaly to soft but do it up with a good quality hex driver.

[YBNORMAL]

Looks like a good idea Bob, I would definitely try to get a steel one made up. I would think there is quite a bit of shearing force on that pin. Although I would think the link pin would be steel already. One way to find out...........got a magnet.....

I guess the parts are so small and so close to the axis of rotation that imbalance would not really come into play.

YB

[carlos]

earlier I though you had had a failure with the pin mentioned in this post.
https://www.helifreak.com/showpost.p...30&postcount=5

[corona007]

Bob, On my old Raptors 30, 50, 90 I just used a roll pin. They are made from spring steel. You can get em
@ Mc Master-carr in imperial or metric.

If you order use the hole size, The pin will come bigger for that size hole.
Also I used a piece of shrink tubing over the pins. Just in case. lol

To pop them back out you will need a pin punch or you can flatten (the tip) of a close to size nail.

Never had a tail failure after that.

[brianapp]

Just put 1/4" of heat shrink tubing on the hub.

[Bob O]

Originally Posted by carlos

earlier I though you had had a failure with the pin mentioned in this post.
https://www.helifreak.com/showpost.p...30&postcount=5

Yes, that pin backed out despite using loctite on it. All the parts were metal.

Originally Posted by brianapp

Just put 1/4" of heat shrink tubing on the hub.

That tip was offered up to me early on. Same with the brass ring/epoxy mod. I wanted something more permanent.

Originally Posted by corona007

Bob, On my old Raptors 30, 50, 90 I just used a roll pin. They are made from spring steel. You can get em
@ Mc Master-carr in imperial or metric.

If you order use the hole size, The pin will come bigger for that size hole.
Also I used a piece of shrink tubing over the pins. Just in case. lol

To pop them back out you will need a pin punch or you can flatten (the tip) of a close to size nail.

Never had a tail failure after that.

The roll pin is a great idea, I actually read about it in a different HF forum, not sure if it was being used on a Compass heli or other brand. If I can't get this one made in steel or if it fails, I'll use a roll pin next.

[carlos]

either wat your mod looks great,looks very functional and safe, Nice one Bob.

[Bob O]

Originally Posted by carlos

either wat your mod looks great,looks very functional and safe, Nice one Bob.

Thanks Carlos. I'd feel a lot better if it was a steel pin. I just don't know where to go to get one fabricated. Or maybe there's already a steel version of this very pin. :

It's obvious the aluminum is strong enough. I put four more flights on today. My primary concern is if it will weaken over time. I guess I could put one of the washout pins (I have at least four of them) through a TR shaft and see how much force it takes to bend or break it.

I wish the 9T pulleys weren't discontinued, as I'd buy a couple and sacrifice one in a strength test.

Does anyone know where to get a 9T pulley all by itself? No matter where I find them listed, they all say out of stock or discontinued. I don't even see the new design silver pulley available by itself.

[Bob O]

Originally Posted by YBNORMAL

Looks like a good idea Bob, I would definitely try to get a steel one made up. I would think there is quite a bit of shearing force on that pin. Although I would think the link pin would be steel already. One way to find out...........got a magnet.....

I guess the parts are so small and so close to the axis of rotation that imbalance would not really come into play.

YB

Yeah, I tried the magnet on the washout pin and no go. The E-clip stuck though.

Sent from my phone

[brianapp]

Originally Posted by Bob O

That tip was offered up to me early on. Same with the brass ring/epoxy mod. I wanted something more permanent.

I have used the heat shrink on the hub in a raptor for three years and the X50 for two. If I need to work on it I can slip it off and then put it right back on. Its permanent for as long as you leave it there. Sometimes the simple solutions work just fine. No need to re engineer the whole thing.

[Bob O]

Yeah, if I had heat shrink of the proper size at that time, I probably would have used it.

Now to get on with finding that part in steel or a place that makes stuff like that.

Happy flying guys and have a great Memorial weekend.

[Bob O]

Three gallons into the mod now and all is well. :-)

Sent from my phone

[Bob O]

I got to finishing up the repairs to my heli from a crash about ten days ago. Although there was no damage to the tail, I figured I would regrease the thrust bearings and inspect the pin.

The thrust bearings were dry so I lubed them up. I pulled the tail pin and found some minor gouging on the pin. This was no doubt caused by the pin rocking back and forth within the hole in the tail rotor shaft, being that the hole in the shaft is larger than the holes in the pulley, and that I had not used a set screw against the pin.

I decided to test the pin to see how strong it was. I was surprised to find that I could bend it around without it breaking. It took quite a bit of force to bend it, but the aluminum was soft enough not to snap under this type of pressure.

I tried the same thing with two different types of screws of the same diameter. They couldn't handle even a slight bending force before snapping like a twig. I had considered using one of these screws with a nut on the end instead of the pin, but definitely will not after seeing how weak they were. A shanked screw would be ideal, but where to find one of the proper size?

So what I ended up doing was replaced the pin with a new one, and then used a socket head screw in the end of the tail shaft in place of the set/grub screw. Seeing how strong the pin was gave me the confidence to tighten a screw against it. Also by using a screw there is a lot more threaded area for locktite to grab and hold it in.

Here's a pic to show the pin with the gouge marks in it. And another pic to show how that pin bent but didn't break compared to the steel screws.





Sent from my phone

[Bob O]

Sorry guys, I won't have a long term report on this mod being that the heli has been grounded while I venture into big electrics.

Sent from my phone