Liftoff (FW) build diary

**Eventorizon** · 30th August 2012, 15:40

That looks beautiful! Ellis is right if you can get that within the 13.6 Kg limit then you can come and play in both competitions.

Going for rear wheel drive only will save weight so that could get you inside as well as making sure you make your pneumatic ram as light as possible.

Keep going, it looks amazing!

**psycho_fling** · 30th August 2012, 15:57

you keep mentioning the weight limit as 13.5kg when it is 13.6kg so.......extra 100g to use

**Liftoff** · 30th August 2012, 16:03

Ahaa

well 100g could make it or break it, so that to my advantage

thanks for pointing it out!

**Liftoff** · 30th August 2012, 20:36

been looking ways to attach hdpe together and from what I can understand, the best method apart from fasteners is welding. I've got no plastic welding equipment so I'll try to fiddle with what I have - my idea is to pass a small gauge wire in the ends to be welded, then press the ends together and connect the wires to a battery, the wire should get hot enough to melt/weld the ends in theory. Anyone tried something similar with some success? I'll give it a go tomorrow and see what happens

**kane** · 31st August 2012, 00:45

Maybe give it a go. I think you'll find a blow torch more effective. Although DIY plastic welding is better for repairs than structural joints.

Possibly using tongue and grove joints would be stronger; or just mitre and bolt the corners.

**maddox10** · 31st August 2012, 05:38

Originally Posted by Liftoff

been looking ways to attach hdpe together and from what I can understand, the best method apart from fasteners is welding. I've got no plastic welding equipment so I'll try to fiddle with what I have - my idea is to pass a small gauge wire in the ends to be welded, then press the ends together and connect the wires to a battery, the wire should get hot enough to melt/weld the ends in theory. Anyone tried something similar with some success? I'll give it a go tomorrow and see what happens

Actualy, the wire idea is being used in industrial piping welding processes. But that requires some expensive machines. It's ment to weld tubes and connections together.
The tool I used was a combination machine. A mirror welder but with attachments for wire-welding.

For mirror welding (the mirror is a polished stainless steel plate). Put the tubes in the hydraulic clamps. Scan the barcode of the parts. The parts get pressed at a certain pressure against the mirror. The mirror gets heated to a certain temperature. When the parts have the temperature desired, the mirror is withdrawn, and the clamps press the parts together. Never seen neater butt-joints.

Wire welding requires elbows and straight connection pieces with the wire in them. But the idea is about the same. Push the cleaned parts together, align. Push the wire-connectors from the machine on the studs on the parts, scan the bar code, and press start. When the buzzer sounds, it's ready.

On HDPE welding equipment. After a few failed attempts with cheaper hot air guns and self build nozzles I got myself a second handLeister Triac S. Still not cheap.... But worth the investment. As the Hannibalito's demonstrate.

**Gabe01** · 31st August 2012, 06:50

I have tried welding with this method before, the joint is always very weak. A routed joint and bolts is the best way. If you want to try the welding, for best results place your wire (very fine gauge) with 3mm spacing across the whole joint. This then will be the same as spacing on the pipe joins (hdpe gas pipe)

**Liftoff** · 31st August 2012, 09:52

just finished the experiments, and after lots of flying sparks, burning wire and melting plastic I managed to get some results :wink:

took some of the tips posted here and the end result looks good - to be honest, I'm really surprised by the strength of the weld, but having said that I did not try to break the weld yet.

started off with thin piece of wire

and locked it in place with a soldering iron along the joint

clamped it an connected it to a 6v battery (had to replace those thin leads as they stared smoking and melting in no time! A pair of jump leads did the job - they got a bit warm anyway!)

Close up of the seam

and finally a test - that's a solid block of steel weighing about 15kg, left it for 15min and didn't break... tried to shear it off with my hands - no good. But I think if I had to clamp it and hit it with a hammer it will give in...