90 Degree VersaPlanatary Drive - Miter Gear Design

grabcad

A 90 Degree Drive for the Vexpro VersaPlanetary4 flavors. Each use different Martin Miter Gear (each available from McMaster). Light duty - 16T@16DP (conservative est 10:1 ratio with 775Pro input) 2X2 square tube Medium duty 18T@12DP (conservative est 30:1 ratio with 775Pro input) 2.5X2.5 square tube (Two subflavors of this flavor THIN and THICK -- thick is stronger obviously) Heavy duty 20T@10DP (conservative est 65:1 ratio with 775Pro input) 3X3 square tubeNote Conservative Estimates are probably 2/3 of true value (can probably use 1.5-2X safely). Also, McMaster sells unhardened teeth, hardened teeth (which Martin makes) will give another 1.5-2X ratioNOTE. Redesigned for Christmas! Based on building one of these, made some changes/improvements.Fixes/updates in this re-release:- fixed some dimensions and ticky tack problems- simplified the housing (gave up some tilt control on the gears but based on the first sample, this is not going to be a problem) much rather have simple manufacture- included drawings for the housing and the gear modifations (more like sketches but the info is there)- made a thick and a thin middle version (18T12DP gear) -- That gear is a BEAST. I am surprised at how beefy it feels in your hand. I suspect that with the thick housing it will be pretty much unbreakable -- or rather it will not be the weakest link, the VP will fail first. Just a gut feel but... - removed the covers for the largest gear version (20T10DP gear) and made the housing thicker. I am very confident that this gearbox will be stronger than the VP. I hope you enjoy the design.UPDATE: 2016-12-08aFixed a lot of ticky tacky problems. Primarily, modified length of 20T10DP gear was wrong.Also, HARDENED TEETH, versions of Martin Gear available from Motion Industries. ~50% cost up but worth it. -- 16T16DP 3/8" bore hardened teeth = HM1616 $37 each (vs McMaster 6529K11 $22) -- 18T12DP 1/2" bore hardened teeth = HM1218 $48 each (vs McMaster 6529K17 $31) -- 20T10DP 1/2" bore hardened teeth = HM1020A $61 each (vs McMaster 6529K23 $43)Dr. Joe J.ALSO. Native CAD files are in Solidworks -- use configurations to easily switch between design options. All the files are in a PackAndGo Zip file. JJUPDATE 2016-12-22: Artur pointed me to this table from Martin. http://www.martinsprocket.com/docs/default-source/catalog-gears/miter-gears.pdf?sfvrsn=14They have HP ratings for each miter gear. Using that I can back out a max effective ratio (recommended by Martin -- which will be pretty conservative). Here is what I get:ONCE AGAIN, let me stress imho these numbers are conservative for a FIRST robot but it is a good point of references and it is easy. YMMV.Using the 10RPM numbers (effectively stall) = ~1Rad/secBig gear HM1020 would be 0.05HP = 37Watts = 37N-m so the max effective ratio is at 50:1 (37N-m/0.71N-m stall torque). I get similar numbers using the 50RPM Big gear HM1020: 0.3HP@50RPM = 223W @ 5 Rad/sec => 43N-m => max effective ratio 60:1Mid gear HM1218. 0.02HP@10RPM = 15W @ 1 Rad/sec => 15N-m => max effective ratio 20:1Mid gear HM1218. 0.15HP@50RPM = 112W @ 5 Rad/sec => 21N-m => max effective ratio 30:1Little gear HM1616 0.02HP@25RPM = 15W @ 2.5 Rad/sec => 6N-m => max effective ratio 6:1Little gear HM1616 0.04HP@25RPM = 30W @ 5 Rad/sec => 6N-m => max effective ratio 8:1Other notes.*** These are for if you STALL the 775Pro, not always the case. *** These numbers use EFFECTIVE ratio not actual ratio. I would use 80-90% per stage on the VP so for example if you used (3) 5:1 ratios, you would have an actual ratio of 125:1 but an EFFECTIVE ratio of something between 70:1 and 90:1 after efficiency is accounted for. *** AND FINALLY, let me stress AGAIN imho these numbers are conservative for a FIRST robot application.*** The Vex 15T 12DP gear that many FRC folk are familiar with, assuming that the teeth are hardened would be able is on that Martin table as well. HM1215 0.1HP@50RPM = 75W @ 5 Rad/sec => 14N-m => max effective ratio 20:1