Metal forming motorcycle hugger

[Screwdriver]

Thought this might be interesting plus I have questions. Been asked to knock up a hugger which I am making out of Duralumin(?) old truck siding.



Made a form out of some scrap wood using one of those rasp things that fit an angle grinder. Rounded off the end of a plastic mallet and have at it.





No idea what I am doing and I guess a sand bag would have been a better option but you run what you brung so... Complex shape with it being curved in both directions but initial tests were going well I thought. My first time at this.



Once I have the gross shape, I started with a smaller metal hammer over a spherical cast ball and check fit over a spare tyre.



Dunno why I didn't think of this before but then I have never done this before. Works very well.



This is as far as I got.



Perhaps ill advisedly I also suggested riveting in some titanium brackets so that's next.

Question though, does Duralumin (is lorry siding Duralumin?) anneal just by heating and air cooling or does it need to be quenched? Pretty sure it's work hardened with a million little hammer blows. How can I tighten up the radius so it follows the tyre diameter a bit closer.

 

[Pigeon_Droppings2]

Thats looking very good...compound curve forming I think is a very difficult skill.

Would a series of mig plug welds pull the metal in maybe? Just a suggestion...I've never tried...and not sure Ali behaves like steel either?

 

[Misterg]

does Duralumin (is lorry siding Duralumin?) anneal just by heating and air cooling or does it need to be quenched?

Air cooling will be fine for pretty much any aluminium alloy in thin sections if you're just want to anneal it (rather than the first stage of solution heat treatment).

I presume you know the tricks about covering the metal with soot, soap or marker pen and then heating it just enough to burn it all off again in order to gauge the temperature.

After annealing, it may be very, very soft.

Nice work, btw.

 

[tigdlo]

Looking good, a sandbag may be quicker for stretching out the middle but your setup looks good to me. Have you been shrinking the edge too?

 

[RichardM]

Anneal as above , I use marker pen for ease.
Do you have access to an English wheel?

 

[Maxakarudy]

You've done a lot of shaping so far without tearing it so well done, to tighten up the radius lengthways you'll need to shrink the edge.
Presuming you don't have a shrinker, then try "tucking" the edge, you might need to make a tucking fork and use as described in the video
As said above, a wheeling machine would make light work of smoothing it, if not further light planishing & sanding would get you there

 

[Screwdriver]

Thanks guys. I think I will try to avoid annealing if it's going to get really soft. It needs to be stiff in use and I don\t want to do too much more hammering!

The edge did get a fair bit of shrinking. It made perfect sense how it happened while I was doing it but the circumstances under which it developed a tuck were somewhat surprising and often appeared to be counterintuitive. At one stage I was trying to increase the curve on the inside by hitting it over the hollow and it started to bulge up!

I think I'll cut it closer to size which should help and then get some tucks going along the edges, see if that helps bring the diameter down. Left it big because I thought I might end up with some fatiguing on the edges but there's only one tiny crack. Guess I may have to anneal the edge a bit, I'll try it hard first.

No English wheel but the "look" is exactly what I was after and it matches the distressed/aged look of the bike (old Kawasaki H2).

 

[Screwdriver]

You've done a lot of shaping so far without tearing it so well done, to tighten up the radius lengthways you'll need to shrink the edge.
Presuming you don't have a shrinker, then try "tucking" the edge, you might need to make a tucking fork and use as described in the video
As said above, a wheeling machine would make light work of smoothing it, if not further light planishing & sanding would get you there

Aha, cross post but just what I was thinking. Good tip regards tucking forks, assume I will have to anneal it - I think it's probably too hard now to bend so easily and cracking is the thing I fear most! I may planish it a bit over an old tyre.

 

[Morris]

Will you be wiring the edge?

 

[Screwdriver]

Will you be wiring the edge?

No that's too much for a first attempt. I may put a slight radius on it if there's time. Has to be done today(!).

I left this to the last minute...

 

[minimutly]

Looking good, a sandbag may be quicker for stretching out the middle but your setup looks good to me. Have you been shrinking the edge too?

This ^ "shrinking" thing, I've watched a good few vids, but damned if I can see how it works - anyone else?

 

[Screwdriver]

This ^ "shrinking" thing, I've watched a good few vids, but damned if I can see how it works - anyone else?

When you have a fold (or "tuck") in a sheet, hammering it down from the sharp end tends to force the material to the side. It actually makes the material thicker because the sides can't just move out of the way. That's how it feels in practice but of course, you can't keep flattening it or it will thin out the material. Clearly if the material gets thicker, it pulls itself in and the width shortens. Keep squashing it and thinner material will spread out and will become wider.

 

[minimutly]

So it folds over itself? Surely this just creates a "layered" section?
Re read and I think what you're saying is it somehow gets hammered thicker?

 

[many_methods]

Yeah you're effectively squashing the material into itself like plasticine

 

[Screwdriver]

So it folds over itself? Surely this just creates a "layered" section?
Re read and I think what you're saying is it somehow gets hammered thicker?

No a fold or "cold shut" is the main thing to avoid but also yes, you do hammer it thicker!



Top right is a "tuck".

Top left is your undisturbed sheet
Next form a tuck which pulls the sheet together, shortening the width
Hammer the tip of the tuck (pointed out top right) as shown in pic 2 left, this forces the tip down but due to triagulation, the forces go sideways where they are constrained by the rest of the sheet
Upshot being, you have hammered the material thicker as if you'd been hitting it "on edge"
Finally bot left, the material is a little bit thicker which makes the sheet a surprising amount shorter

 

[Morris]

So it folds over itself? Surely this just creates a "layered" section?
Re read and I think what you're saying is it somehow gets hammered thicker?

Much as I hate referring to YouTube, have a look for videos on shrinking by Wray Schelin or Ron Covell. They go into detail and explain it well.

 

[Morris]

No a fold or "cold shut" is the main thing to avoid but also yes, you do hammer it thicker!

View attachment 529194

Top right is a "tuck".

Top left is your undisturbed sheet
Next form a tuck which pulls the sheet together, shortening the width
Hammer the tip of the tuck (pointed out top right) as shown in pic 2 left, this forces the tip down but due to triagulation, the forces go sideways where they are constrained by the rest of the sheet
Upshot being, you have hammered the material thicker as if you'd been hitting it "on edge"
Finally bot left, the material is a little bit thicker which makes the sheet a surprising amount shorter

You've missed the part where you trap the tuck. It will still work without but not as effective.

 

[Screwdriver]

Much as I hate referring to YouTube, have a look for videos on shrinking by Wray Schelin or Ron Covell. They go into detail and explain it well.

Yeah, that's what I did! It is incredibly relaxing to beat metal I discover. Don't know how long I spent with the smaller hammer over the cast iron ball but probably an hour. If you're off by a few mm you get a deadblow and a dull thud. Get it right though and the hammer rebounds as if its alive and make a really satisfying noise.

Can't explain it (maybe I should do a video) but it is incredibly satisfying when you feel like you're getting it right and the material is doing what you want. Plus I really like the look of all those tiny hammer marks!

 

[Morris]

Trapping the tuck

 

[MattF]

I think I will try to avoid annealing if it's going to get really soft. It needs to be stiff in use

Duralumin age hardens.