Help with STA

[GreenDiverDown]

I have a Halcyon STA that I have been using for about a year now. Now a problem has come up. The 5/16 x 1 1/4 in. SS carriage bolts no longer grab the STA when spinning on the wingnuts. In fact, even when new they didn't grab very well. Halcyon drills a hole big enough for the square part of the carriage to fit through. Then they cut four slices in that hole so that the corners of the carriage will grab and you can tighten down the wingnut. Looking at the carriage bolt it appears that the corners have been rounded down. New bolts sorta fixed the problem but even the new bolts have slightly rounded corners and spin a little. Hmm...I guess I could spot weld the bolt to the STA but I'd rather not. Too bad they didn't cut squares in the STA like in Fred's plate. (I have a FredT heavy STA...much thicker than the Halcyon...and he has counter sunk his holes and uses a flathead bolt. This works much better than Halcyon's approach. The holes in his BP are square.) Anybody have an idea how I can get my bolts to grab better?

SA

 

[Scubaroo]

As soon as I can track someone down locally who can spotweld SS, I'm going to get my FredT light STA and bolts spotwelded - I leave my STA on the tank almost permanently, so I'm often undoing/tightening the bolts and wingnuts.

In the meantime, some split or lock washers may help. Haven't tried them yet though.

 

[matt t.]

I would have them spot welded. The OMS single tank adapter comes spot welded from the factory and works great!

 

[MechDiver]

You might be able to peen the edges of the holes and get creative with a small file, but I agree with the others; have them spotwelded.

MD

 

[FredT]

Short of welding it anyway

1. JB Weld the bolt to the STA plate. It's removeable with a bit of force, but reasonable torque wont dislodge it.

2. A product made by 3M Aerospace called DP-420 insted of JB Weld. It has a bit higher shear strength but is still removable with a BFH.

3. Devcon makes a product called steel putty. Works for most moderately loaded products, and loctite make a thread repair putty that is almost the same thing performance wise.

For all the above cleaning and roughing the mating surfaces to provide a bit of "tooth" is VERY important. Many epoxys take a week to fully cure, even if they fixture fairly quickly. so don't rush the test.

Scubaroo,

Have a weld shop place two small spots on the STA with 316 rod in the slot location of the screw. If the screw needs changing the BFH will break it free, then the weld remains will prevent the replacement screw from turning.

FT

 

[mddolson]

I epoxy cemented the carriage bolts directly to my STA.
I roughed up the surface as previously mentioned with 80 grit sand paper.(my STA is aluminum)
Them mixed up some epoxy cement (devcon is also what I used).
Applied it liberaly, to the heads of the bolts, pushied them in the holes, held them inplace with a weight and block of wood over night.

It been 3 seasons now no problems.

MikeD
:blfish:

 

[buff]

I have decided that JB Weld or Loctite is the secret to a good life.

I use it everywhere-scuba gear, bike equipment, breakfast cereal.

 

[GreenDiverDown]

Thanks, guys. I appreciate all of your suggestions. I guess if I'm going to 'permanently' fix the bolt to the STA then I'll just weld it...there is a welding shop right next door.

So, Fred...

Were would be the best place to place the "two small spots"?

Here...

 

[GreenDiverDown]

Or here?

Thanks.

SA




Or does it matter?

 

[MechDiver]

Stephen Ash once bubbled...
Or here?

Thanks.

SA

Or does it matter?

I wouldn't weld on the side that fits against the wing.

MD