Bending Small Metal Parts (3mm Steel)

[madmonkey]

Hi guys,

How would you guys go about bending these small parts. They are the spokes for the Fowler Showmans Traction Engine. I need to put to bends in each one, 12 pieces for each of the front wheels, so ideally something easy to repeat and get consistent results. I had the spokes laser cut, but they can't bend the pieces. They are 3mm mild steel. I have a couple of spares for practice...

Thanks

[barlowworks]

Hi Madmonkey

What size are the pieces and where do they need to be bent and by how much.

Mike

[madmonkey]

Jun 29, 2018 18:26:12 GMT barlowworks said:

Hi Madmonkey

What size are the pieces and where do they need to be bent and by how much.

Mike

Hi Mike,

I've attached an image of the approximate bend positions. The overall size is about 3.5" and the bends are approx 156 degrees. I have a 3D printed piece that I can use to compare.

Hope this helps. Thanks

[Deleted]

That looks quite short for 3mm and two bends. You may need to anneal it first. I would make a couple of jigs that use the holes already there. For the end with 3 holes make two plates that bolt together sandwiching the part between, the top of the jig for one half being where the bend is. For the other half of the jig I'd have it angled away from centre a little more than what's required so that you can bend each one to the same angle. I'd do the same for the single hole end but for this on one side I'd machine a recess to the hole at 90 degrees to the top (fold) edge, this will ensure all bends are at 90 degrees. The other side I'd do the same as before, angle a little more than required to get all at the same angle, I'd assume both ends have the same angle. Make the recess just shy of the 3mm so that there's no risk of play/movement when when the bend is done.
Hope that makes some sense, not easy describing whats in my mind...Don't forget to allow for bends to suit that metal thickness, as it's only an angle I wouldn't expect it to make much difference but I would assume that the spokes need to be a set length after being formed so do a test on the spare ones adjusting if required to get the correct spoke length...

good luck

Pete

[jasonb]

When I did my fowler and Minnie for that matter I just held them by the palm in the vice with the rest of the spoke pointing upwards then with an adjustable spanner held about 1/4" up from the vice gave the spoke a quick tweak. You soon get the feel of how far to bend them so they sit flat on the tee ring and just touch the edge of the slot in the hub. Use the same method to bend the hub end. Don't leave more that 1/4" between vice and spanner otherwise you end up with an "S" shaped spoke rather than one with two neat bends.

If it were a larger engine then worth making up a jig to press them but not worth it on the smaller 2" engines

[Deleted]

Is 3mm correct? that seems out of scale to me, looking at Jason's picture, if this was the same scale I'd be thinking it's much, much thinner, 1mm or less? I will state though that I know little of traction engines...

[jasonb]

2mm on my fronts and 2.5mm on the rears. That's the nearest metric stock thickness at 1/6th scale for 1/2" and 5/8" on the original.

[Deleted]

How long are your spokes Jason...they look much longer than 3 1/2 inches if they are 2mm thick?

[jasonb]

About the same as Monkey's the front wheels are 7.5" dia so allowing for hole through the hub and thickness of rime would make them about 3.5" . The rear wheels are 12" diameter so about 5.5" for the spokes. They were laser cut over length and then finally trimmed once bent and laid in place on the building jig.

[abby]

I would do them under my fly press !
Dan.

[madmonkey]

Thanks for the information. I did wonder if they would need annealing especially after being laser cut. I have a few practice pieces so I can experiment.

The plans stated 1/8" so just opted for 3mm. Thinner would be easier. Im not sure if i've calculated enough material for the bends so I could be getting them redone if Ive really messed up. Luckily I can drill the holes to suit in the hub, but I could go thinner if 3mm is too difficult to work with. The overall diameter without tyre of the wheel is 8".

I like the idea of using the vice and an adjustable, I wouldn't have thought I could get a nice bend but those photos look great. Im going to try this first and then look at maybe a jig.

I was thinking of one of those brake presses for the vice, that was on my test list as well.

[ettingtonliam]

I had this problem on my 4" scale Tasker tractor. I used JasonB's method, but made a setting tool rather than using the spanner. It was just a steel block, slotted to fit over the spoke, and welded to the end of a 2' length of 1/2" dia bar. As Jason says, grip the palm in the vice, slot the setting tool over the leg, and tweak it. I made a gauge out of 16G plate, so the angle was correct on each spoke. Then repeat the operation for the second bend, checking that the offset is correct and both ends are parallel. I didn't drill the end until I'd completed the bending, again using a jig to make sure all the spokes were the same.
To build up the wheel, I made up a base board out of 3/4" ply, with another ring of ply screwed to it, this second ring being a close fit to the inside of the tee ring. A central peg was a close fit to the bore of the wheel hub. With the tee ring and hub clamped down, I could then offer up each individual spoke, checking the offset and adjusting as necessary, and finally trimming the end so it was a close fit in the hub slot Finally, I drilled through from the spoke into the tee ring and hub, tapped the hub, and bolted the spoke to the tee ring, for rivetting later. Turn the wheel over and repeat for the other side. The result were pretty good, the wheel spun true when I tested it. I'd straked the wheel before I spoked it, wheels on a 4" engine, even on a small prototype like the Tasker get pretty heavy to handle when you are rivetting them.

[jasonb]

Your spokes are likely to be CR4 or S275 which are the common laser cut steels and they are soft enough to bend without annealing. Depending on the cut you may just want to quickly drawfile the edges and ease the edges so they are not sharp. I was thinking last night, I said have the spanner 1/4" from vice but I think I went closer say 3/16 on the palms and 1/8" on the hub end where the full size had no bend so we need to keep the bend a straight as possible with the usual construction method.

Also remember that the rear ones will need different bends on some to suit the lobes on the rear hubs, same applies to the fronts you will need an inside set and an outside set due to the dishing and the palms all being on one side of the flange.

The small bending jaws that fit in the vice won't be any good for this job as unless you are bending to 90degrees you will get a very large radius bend as the three points of contact when you first close them up act much like pyramid rolls or 3 point benders. The 3 point method does have it's uses, the 3mm x 3/4" tyres you can see fitted to the front wheels were bent tat way not rolled and fitted the rim very well and the rivits did not have to pull them onto the rim.h

[madmonkey]

That's great! I'll have a go over the weekend if I get time although I think the Mrs has other plans... I'll post some photos of how I get on!

Thanks again

[ettingtonliam]

The questions you are asking are standard problems when modelling traction engines. I know they are getting a bit long in the tooth, but I suggest that you buy and read either Len Mason's book on building 'Minnie', or Hughes on building the Allchin.
One advantage of the setting tool I described earlier is that if you chamfer the end of the slotted block, you can get the bend to start at the top of the vice jaws, and get a really sharp bend.

Whereabouts in the West Midlands are you?

[madmonkey]

I'll have a look for those books. I'm not a machinist by any stretch, I've wanted to build a traction engine for years, but obviously there's a lot of pitfalls for someone with no building experience, hence the questions. Google helps but not always.

I'm in Solihull, not far from Birmingham.

Edit. Not far, not bit far!

[jasonb]

The more upto date book is " Scale Model Traction Engine Design & Construction" by Edward George, again out of print but they do show up from time to time. The Minnie one is good too but attracts a premium price.