Welding Tips and Tricks

I need some suggestions on how to weld a bracket for a fuel tank. It's hard to tell from the pictures below (I'll take more tonight) so I'll try to describe what I'm trying to do.

The fuel tank has an odd mounting pad with three 1/8" raised discs used as indexing pins, the center pin has an integrated nut.

The tank will need to hang vertically (it's laying on it's mounting face in the pic, the motor will be above the tank).

There are two vertical tubes on each side and a horizontal tube directly above the tank. I was thinking of using 2" angle on the bottom for support (mounted to the vertical tubes) and cut a plate to match the mounting pad and weld that to the angle below and the tube above.

There's quite a bit of vibration so I'm concerned the welds wont hold and not sure that welding it is the best option.

All the material is 6061-T6 and the tube is .750 OD with .058 wall, I have some .125 sheet and angle but since this is a flying machine I'm trying to save as much weight as possible.

Suggestions are welcome. I'm a hobbiest welder so I don't always see things the way people who weld often do.

Thanks!








Link to album for bigger pictures: https://picasaweb.google.com/1108624968 ... directlink

Form fitting saddle and wrapped springs to prevent chaffing or Bungee cords!! replaced frequently.

Warhawk,

That appears to be the prop cage for a powered parachute? I have to say I agree with Rick on the saddle idea... A couple of 16 ga. by 3/4" straps for a small saddle to support it, with strips of 1/16" Buna-N as padding. I don't agree with the bungee hold-down, though. I think I'd clamp it down with nylon straps as could be cut from a 1" "ratchet strap". The ends of the strap should be doubled, and a hole for a #10 machine screw melted through each end with a soldering iron. Use a large washer on the nylon.

This is durable, vibration resistant, and will stand up to sunlight for several years. Most of all, it's very light.

The homebuilder's rule: Simplicate, and add lightness.

Steve S

As my Dad used to say when he was building aircraft..."Thinking of adding a part? Throw it up in the air. If it comes down, it's too heavy!"



Kym

For what you refer to as disc, I'd have a plate with vibration damping grommets or bushings installed the disc would rest in. Then as already been suggested, I'd also go with metal cushioned strap(s) to hold the tank in place.

The link above is for McMaster-Carr; if you are not familiar with them, this site is worth browsing. Especially if the area you live in is limited on materials, supplies, tools, etc.. that can be found easier online.

Otto Nobedder wrote:Warhawk,

That appears to be the prop cage for a powered parachute? I have to say I agree with Rick on the saddle idea... A couple of 16 ga. by 3/4" straps for a small saddle to support it, with strips of 1/16" Buna-N as padding. I don't agree with the bungee hold-down, though. I think I'd clamp it down with nylon straps as could be cut from a 1" "ratchet strap". The ends of the strap should be doubled, and a hole for a #10 machine screw melted through each end with a soldering iron. Use a large washer on the nylon.

This is durable, vibration resistant, and will stand up to sunlight for several years. Most of all, it's very light.

The homebuilder's rule: Simplicate, and add lightness.

Steve S

that tank with fuel,looks like some kind composite, is going to expand and shrink with temp change why I suggested something flexible. Frame suggests an ultralite

You are correct, it's a Paramotor frame that I've been building. Most of the tanks on production frames are molded to fit the frame and the frame actually encases the tank.

For this frame however, the plans leave it up to the builder since the tank configuration is unknown.

I have an account with McMaster Carr and have spent way too much money with them

I have it mocked up right now and did plan to add a nylon strap around the whole tank but I'm trying to make those indexing circles work to keep the tank from rotating.

I have considered taking a piece of 0.125 sheet and cutting it to mach the tank pattern and either bolting or welding it to the upper and lower horizontal supports.

Looking at the installed configuration, I don't see the need to use those locator keys. I'd use that slot in the top of the tank between the fill and the ports... Attach the nylon strap I suggested to a small tab on that top cross tube, run it through that slot, and attach the other end to a tab on the flat-bar that's at the base of the tank. This gives redundancy for the threaded attachment, and anti-rotation at the same time, for almost no extra weight.

Steve S