Swaging, crimping and peening

With help from the forum setting up my rotary table, I've finished making lots of non-standard Meccano pinions and I'm looking at making some larger gear wheels. Cutting the teeth on the gear discs and machining the bosses present no problems, but joining them together does. Are they pressed using a special die, or swaged or crimped? What sort of pressure and tool would be used, what profile should be turned on the boss? Could it be done in a mini-mill etc.? Any advice would be very welcome. I have thought of using a miniature collet but I would prefer to do it the Meccano way.

As many of us (including me) cannot remember what is special about the Meccano Way, you might get more helpful responses if you could kindly remind us. A picture, perhaps?

Regards, Tim

Surely you can't have forgotten these? Crummy image, apologies. Swaged over using some sort of single operation press tool I expect?

I think Chris does not know what the Meccano Way is, hence asking. I have some Meccano gear wheels that rotate on their bush but mostly they are still firm. I have never taken one apart but would expect to make a number of nicks, or 'keyways' in the edge of the hole in the plate embryo gear and then press/stamp the end of the bush over with sufficient force to extrude some metal into these keys to hold it.

In that case, it might be a solution to make the flange a bit wider than normal, and use soft solder to hold the boss to the gear. The larger area will add strength as it all has to shear at once. At the same time, no softening or distorting of the gear due to heat or bashing.

If I understand you ...

Cheers, Tim

Small Meccano gears appear to be solid. Muzzer's photo shows how the larger sizes are made. I had some old gears with loose bosses and managed to restore them with a peening hammer. I'm sure they would have been pressed in the factory with a die shaped to neatly turn the edge of a rim left on the boss. Wouldn't be difficult to turn on a lathe, mild-steel be OK for light use. More pressure than I would care to put on a mini-mill, but easily done in a vice I would think. Can anyone advise about annealing?

Dave

Dave, as you say, the small gears are all machined from solid, which is what I've been doing recently. What you suggest with a die and vice is the way I've been thinking, but I think it would need a jig to keep the gear disc perpendicular to the boss axis, the gear discs would be about 1/16th thick and up to 3" in diameter. The bosses are 3/8" diameter.

Looking at my old Meccano gears they look like Muzzer's picture, but not as neat. There is some evidence of rotary action on the central boss. The edges of the boss where it has been folded over are showing signs of cracking, and the cracks are not radial. So I'd suggest they used some sort of rotary swaging. Whatever method was used the bush would need to be pretty ductile.

I wouldn't use my Bridgeport mill to attempt swaging a gear like the Meccano one. I think you'd need a proper arbor press or flypress.

Andrew

A small version of the eye tool at the top of this photo might do the job, if the brass was annealed first.

Neil

Edited By Neil Wyatt on 04/09/2017 19:02:07

I'd try glue first. It only needs to hold the disc in position on the boss long enough to press the swage. My main worry is squeezing the brass so that it flows rather than splits. It may need to be softened first and then the whole gear re-hardened afterwards. I've never tried heat treating brass, so let's hope an expert turns up!

Dave

Chris
​The process for fixing is called rotary riveting. Google it to see how it works. Basically it combines spinning with pressure. We used to make a range of stainless steel yacht fittings where spacers or small shafts were fixed to side plates. The action which is akin to a wobble keeps the material moving and prevents cracking due to work hardening. It is extremely quick and the geometry of the parts is very simple.
​The tool is a bit more complicate but if you have a standard size boss you only need one set of dies.

Do you think a rotary broach with the proper tooling would work?

Loctite would be the modern way of doing it, I reckon.

If not, a riveting punch for a hollow rivet might do the job.

Edited By Hopper on 05/09/2017 01:11:40

A number of years ago I made some 1 inch Meccano pulleys, that needed a 2 piece die to form the shape of the V in the two halves of the pulley, then I rivited the hub into the wheel. Made most in brass, and when I ran out of that used galvanised iron sheet.

Ian S C

Tim, is that process called orbital rivetting where the punch rotates at an angle to the vertical?

John - Not really. Chris has it where the punch rotates at an angle to the vertical. The best analogy I can think of is a spinning top where the point stays in one place but the main body orbits creating the angle. The beauty of the system is that no heavy presses are necessary. We used standard drill presses.

​This was in a production environment with many thousand operations per day. In a home workshop I would probably take the Loctite option or even very thin super-glue applied after a very light peen.

Chris,

If you want to reproduce the visual detail of the Meccano fixing, without the specialist machinery that Tim mentioned ... have a look at Figure 9 in Laurie Penman's article here: **LINK**

http://www.awci.com/wp-content/uploads/ht/March2012.pdf

[wow, that took some finding]

Watchmakers often just use the staking tool; but for clock [and Meccano] sizes, this ^^^  is much more appropriate.

MichaelG.

.

For reference, here's Roger Smith using the Staking Tool:   https://m.youtube.com/watch?v=J_bQu8D3Tdg

Edited By Michael Gilligan on 05/09/2017 11:19:42

In musical box governors hardened-tempered steel pinions needs to be fitted very securely on to the their brass wheels. For that the part of the pinion that is pressed in too the bore of the wheel is larger in diameter, 0.5 mm or more. The turned down teeth of the pinion that is pressed in the wheel act as cutters. Everything needs to be lined up square and the pinion centered with a bush and pressed into the wheel with a staking tool or a press if you have larger wheels, a vice is not accurate enough. After that the pinion is riveted on the otherside to make the fit definitive. Most important is that everything is as square and accurate as possible and the brass wheel has good support. Niko.

Edited By speelwerk on 05/09/2017 11:59:51

Oh this is about attaching gears..........I thought it was related to preparation for a night out!

I couldn't find a damaged Meccano gear to investigate but this is what the boss hole in a 3" pulley looks like:

You can see that the hole isn't round, it has eight lobes cut into the inner circumference.

Other than the lobes being about 3/16" in diameter, I couldn't work out the Imperial base. Hence the dimensions are in mm. Apologies to Meccano purists for using metric and also to anyone offended by my drawing package suggesting I can measure accurately to 0.0001mm! Please read about 9mm, about 2.4mm and about 8.4mm. ±0.02mm

Dave

Edited By SillyOldDuffer on 05/09/2017 14:42:52