Right angle/ bevel gear boxes.

[kerosene]

don't you get quite a bit of losses from the magnet setup? You are creating unintended electrical currents that basically heat up the parts.
If its Rick - I am sure he has done his homework just seems like magnets wouldn't be the best choice.

[viking north]

Just skimmed thru this thread si if i'm duplicating a pev. post forgive me. The simplest right angle drive i've ever seen is the arrangement used to drive the wheels on a low priced snow blower. A rubber tire driving a flat disc. By moving the tires circumfrencial contact on the disc you have a wide range of range of drive ratios. Old snowblowers are dirt cheap and parts are still supplied by aftermarket companies.--Geo.

[portacruise]

Levitated magnets generate no current, but these are moving so you may have some very small losses due to eddy currents. Still would be more efficient than any other gearing system besides all the other side benefits:

http://www.mgt.com.au/index.php?pageId=6924

P.

Originally Posted by kerosene

don't you get quite a bit of losses from the magnet setup? You are creating unintended electrical currents that basically heat up the parts.
If its Rick - I am sure he has done his homework just seems like magnets wouldn't be the best choice.

[Jeremy Harris]

That magnetic drive looks to be a superb idea, very low losses, automatic torque limiting and pretty easy to build. There won't be any eddy current losses as long as the magnets are kept clear of stationary bits of metal and I suspect that it might be possible to get away with using thinner magnets than the ones that Rick has used. Most PM motors of this sort of torque output seem to be able to work efficiently with magnets than are around 4 to 10mm thick, so I'd think the same might apply to this drive system. Neodymium disc magnets with countersunk mounting holes drilled in the centre can be bought as opposing polarity pairs fairly cheaply (they are made for door catches). I have a couple of dozen 20mm diameter, 3mm thick ones lying around somewhere and I'm tempted to have a go at replicating Rick's drive.

It's a shame Rick isn't here on this forum any more, I miss his innovative approach.

Jeremy

[kerosene]

I guess I am wrong then.
Looks like Will is using rather large diameter to help manage the torque.
Interesting regardless.

And I second that Will is missed here. I don't know what drove him off but I think it might have started with A...

[messabout]

Viking North mentioned a useful variation on the problem of right angle drives. Way back in the day, an impecunious friend asked me to build such a device. He was going to use it on a small 19 foot cruiser that was to be powered by the equivalent of a lawn mower engine. About 10 HP as I recall. In spite of my skepticism he insisted that I build it. I did. The plate had a shallow indenture in the area of its' supporting shaft. The rubber drive wheel was movable towards or away from the plate centerline. Thus he had a variable gear ratio, and he also had a neutral by sliding the rubber wheel to the middle of the plate where the indenture was. Slide the wheel across the centerline and you have a reverse.
It spite of my misgivings,( I did not think the contraption could transmit enough power) he installed it and the whole deal worked perfectly and it lasted for several years before the need to replace the rubber wheel.

I had, and still have a small factory replete with a full blown machine shop where we can do such stuff. The business and product end of the firm has very recently been sold and within a month or two, I will be just an old fart with nothing to do. And I'll be sitting on a fairly decent machine shop. I might just build one of those things or maybe go to the drawing board and design up a real gearbox with anodized aluminum housing. (we have anodizing capability too)

[Squidly-Diddly]

I couldn't find on company website or elsewhere.

[portacruise]

Originally Posted by Squidly-Diddly

I couldn't find on company website or elsewhere.

I believe this is a fairly new patent and the company is not up to speed yet, for off the shelf components. They do list a US contact but MGT is not referenced in the contact's online directory. Maybe a phone call would turn something up. I suspect MGT is focusing on large, lucrative custom designs, at least that's what I would do until things were rolling.

Jeremy, you read my mind on the use of thinner and lighter gearbox designs, now that Rick has shown the concept works. Some very powerful and extremely thin (0.8mm?) magnets are in production which might work with the proper high strength glue combined with mechanical interlock to secure. Some of these thin ones are way too powerful for door catches. The powerful magnets have to be handled with concern for shock, as they shatter when not gently lowered to a steel surface. http://www.kjmagnetics.com/specs.asp

Porta

[Jeremy Harris]

The magnets I have are pretty strong, they are made from N38 neodymium, with a flux density of around 12,0000 G. I agree, they do seem too powerful for door catches (they will give your fingers a nasty nip!) but that's what they were sold as when I bought them. I have 40 of them, 20 of each polarity. They would be easy to use for something like this, as they have a 4mm countersunk hole in the centre, which would make fixing them to drive discs pretty straightforward.

The only downside of a drive like this, as far as I can see, is the need for a large diameter in order to transmit high torque. Rick's experiment showed that this type of drive can handle the sort of torque loads needed, though. A lot will depend on the gap between the magnets. If this air gap can be made very small then the torque would be increased, just as it is with a motor. The key would be making supports and bearings capable of holding a consistent gap of around 1mm or less between the magnets. From Rick's video it looks like his air gap was quite large, which may have been limiting his maximum torque.

Jeremy

[portacruise]

Originally Posted by Jeremy Harris

The magnets I have are pretty strong, they are made from N38 neodymium, with a flux density of around 12,0000 G. I agree, they do seem too powerful for door catches (they will give your fingers a nasty nip!) but that's what they were sold as when I bought them. I have 40 of them, 20 of each polarity. They would be easy to use for something like this, as they have a 4mm countersunk hole in the centre, which would make fixing them to drive discs pretty straightforward.

The only downside of a drive like this, as far as I can see, is the need for a large diameter in order to transmit high torque. Rick's experiment showed that this type of drive can handle the sort of torque loads needed, though. A lot will depend on the gap between the magnets. If this air gap can be made very small then the torque would be increased, just as it is with a motor. The key would be making supports and bearings capable of holding a consistent gap of around 1mm or less between the magnets. From Rick's video it looks like his air gap was quite large, which may have been limiting his maximum torque.

Jeremy

I think Rick was trying to stay away from machining in his prototype design. Those catches you have are rated higher than I expected at N38. Is there an inverse square law in play with distance and torque involving magnetics, of is it even higher? The MGT information indicates they can be fashioned for some applications so there is essentially no force on the shaft bearings. Perhaps they are somehow placed on either side so that forces are counterbalanced? Maybe multiple interlocking disks could be used to increase torque and thus reduce diameters? More complex design though....

Porta

[Jeremy Harris]

It's a cube law relationship between the force that the magnets can exert and the distance between them, hence the importance of getting the air gap as small as possible. As you rightly say, getting small gaps without machining is hard, but the reward in terms of increased torque transmission from a given diameter of disc would make it worth aiming for.

I think that you're right about using pairs of magnets either side to get rid of the axial force component on the bearings. There's an illustration on the MGT site that looks as if they might use an arrangement with a double disc on one shaft with a single disc fitted inside it. This could be made to run with pretty small gaps and hence transmit a lot of torque, but not for a right angle drive, I think. I think it might get around the need for a lot of close tolerance machining, too, as the only precision part would be the spacer between the two discs that sets the gap. The discs should be self-aligning, because of the magnetic interaction, and could fit to shafts just like a pair of pulleys.

Jeremy

[mrosupply]

https://mrosupply.com/products/255-Miter%20Gears