Hand Ergometer

**FatFreddie** · 28-06-2013

I just printed some 1mm thick test pieces.

I loaded the 15 and 30 tooth gears into cambam and generated a profile with the built in generator and it was exactly the same outer and root diameters (just a bit more lateral clearance in the root) so I suspect you're right about the ring gear - unfortunately cambam doesn't do ring gears (I've bumped a thread asking for them).

Measured OD on the 30t gear is 40.0mm and 21.3mm on the 15t and the tooth tip diameter on the ring gear is 72.7mm and the root diameter is 76.4 (near as I can tell - it's a bit flimsy)

**irving2008** · 28-06-2013

Originally Posted by FatFreddie

I just printed some 1mm thick test pieces.

I loaded the 15 and 30 tooth gears into cambam and generated a profile with the built in generator and it was exactly the same outer and root diameters (just a bit more lateral clearance in the root) so I suspect you're right about the ring gear - unfortunately cambam doesn't do ring gears (I've bumped a thread asking for them).

Measured OD on the 30t gear is 40.0mm and 21.3mm on the 15t and the tooth tip diameter on the ring gear is 72.7mm and the root diameter is 76.4 (near as I can tell - it's a bit flimsy)

OD for MOD1.25 = (N+2)*1.25, so 30T = 40mm and 15T = 21.25mm.

tooth tip dia on ring gear should be (N-2)*MOD = 58 *1.25 = 72.5mm and root dia 78.125mm which is correct on drawing...

**FatFreddie** · 28-06-2013

Ok, looks like it's a problem with printing the internal features - let me have a look at it over the weekend - trying to learn Hadoop (if you don't know, you probably don't want to) at the moment and it's not conducive to concentrating on other stuff :-(

**FatFreddie** · 01-07-2013

Ok, some progress. I've now got a set of gears that mesh reasonably well but I'm not happy with the print quality so I'm going to try a different slicer - the one I'm using at the moment is Sli3er and it's fast and easy to use but it doesn't seem to be the best quality. I was using Skeinforge before which is better quality output but not very friendly - I'll have another go with that over the next couple of days.

**irving2008** · 01-07-2013

Originally Posted by FatFreddie

Ok, some progress. I've now got a set of gears that mesh reasonably well but I'm not happy with the print quality so I'm going to try a different slicer - the one I'm using at the moment is Sli3er and it's fast and easy to use but it doesn't seem to be the best quality. I was using Skeinforge before which is better quality output but not very friendly - I'll have another go with that over the next couple of days.

Thanks for your efforts on this. I'm in the process of drawing up slightly modified gears, the main difference being improvements to better support/locate the bearings and space the sun gear off the rotor boss - I may increase the thickness of the gears slightly. I'm also redrawing the supports, the rotor bosses and the planet carrier. I was thinking of 3D printing the carrier but I don't think the boss would be strong enough to take a grub screw to fix it to the axle (but what if the boss was thicker and had a slot for a nut to be inserted?). The other thought I had was 3D printing other components, the rotor bosses for example. I'm not sure about the cranks or the handles from a strength perspective, need to run the numbers. Also do you have any way to calculate the cost of a printed component?

**FatFreddie** · 01-07-2013

No problem, I'm enjoying having something constructive to do with the machine. Work is a bit binary at the moment so apologies if I go missing occasionally.

I had thought of printing some of the other parts - once I get something that can be strength tested we'll know better what's possible. I have had some unexpected breakages in the past but that was with mounting brackets where I think I underestimated the shock loads. One thing to bear in mind is that things like splines which would normally be difficult are relatively easy with 3D printing. The main problems are fine tolerances and overhangs so a spline would be best if it was tapered or with pinch bolt.

I haven't bought any filament for a while but I think it's around £30 a kilo. Partially hollow parts are the norm so material usage is quite efficient.

**irving2008** · 01-07-2013

Originally Posted by FatFreddie

No problem, I'm enjoying having something constructive to do with the machine. Work is a bit binary at the moment so apologies if I go missing occasionally.

I had thought of printing some of the other parts - once I get something that can be strength tested we'll know better what's possible. I have had some unexpected breakages in the past but that was with mounting brackets where I think I underestimated the shock loads. One thing to bear in mind is that things like splines which would normally be difficult are relatively easy with 3D printing. The main problems are fine tolerances and overhangs so a spline would be best if it was tapered or with pinch bolt.

I haven't bought any filament for a while but I think it's around £30 a kilo. Partially hollow parts are the norm so material usage is quite efficient.

OK. Attached are image and DXF file for the 3D printable modded sun gear and rotor boss which now include a seat for a 15 x 10 x 4 magneto bearing. these go either side of the rotor and are joined by 25mm M3 cap headed bolts and captive nyloc nuts. Are these printable?

Crudely each contains 1.25e-5 cubic metres of material, which means 0.02kg of PLA