Happy thanksgiving everyone from our shipyard to yours! We're steadily working towards stuffing tube day! Measure twice cut once and all that that stuff. Passed afew milestones with the mounts and gearbox, things are lining up nicely. Still need to bench test the setup, but I'm feeling confident enough to post the files if anyone would like. 550 Drive Motor w/ 10-tooth 32DP Pinion Gear View: https://www.amazon.com/dp/B075WZ21JW?psc=1&ref=ppx_yo2_dt_b_product_details Traxx 28-tooth 32DP https://traxxas.com/products/parts/1526 This setup gets about a 3:1 reduction ratio Additional details to come, Happy Holidays!
Slick looking gear box, keep up the good work! Something that sticks out to me, and those with more experience please chime in, but I think 40000RPM motors may be a little too fast/low torque for drive motors, even with a 3:1 reduction. I could be totally off base but my 15lb, 26 sec I-boat which has I think 15k RPM 550 motors on 7.4v and an about 3:1 reduction still has a significant ESC reduction to make speed. So you might have trouble keeping the speed down and/or have poor acceleration? Or I could be totally wrong and you’ll be fine. Anyways, something to look out for and keep posting updates!
At 2.8:1 you’re looking at over 14k at the props. I’m sure you’ll get that sorted when it is time to speed test. Swapping motors isnt hard.
A couple suggestions for the gearbox It looks like the shaft is being supported by thin ABS as a bearing surface, which I don't expect to last under load. It's better to run the stuffing tube into the gearbox and to rely on the stuffing tube bearings/bushings (typically Oillite bushings) to be the contact surface with the shaft. Having the gearbox be in contact with the stuffing tube spreads the normal force from the gears over a larger area. Take a look at the Traxxas Villain gearbox design, several guys have draw up printable files and posted them on here It's not clear how the motor is attached to the gearbox, looks like maybe friction tape? Friction-based mounts can work in certain applications, I try to avoid them for a gearbox design since getting proper gear engagement is very important. Typically gearboxes will use the bolt holes on the front of the motor can with slots in a plate to allow setting proper engagement between the gear. Motor replacement can still be fast with the bolt-hole mounting, just ensure there is space to get access to them (don't put a cross member in the way)
Good call @Kevin P. That shaft is going to chew through that mount in seconds. You really need shaft bearings to support it. What are you using for stuffing tubes?
I completely didn't know/ realize there's different rpm models?? I thought a 550 was good as any 550... Those are going back, lol Being a slow 38 second boat, what rpm 550's should I be looing for? These are the stuffing tubes I'm going to use, they accept a 4mm shaft & I modified them with zerk fittings (for ease of maintenance) All the forces 'should' be acting on these and into the hull. As others pointed out the thin ABS bearing surfaces, these are 'templates' a replaceable part of my gear box that allows me to dial in my gear spacing/engagement with out having to reprinting the whole motor mount assy. Looks like I'll need new motors (of the proper rpm). Possibly new pinion gears and remake my templates to get the gear spacing right. Bummers, was so looking forward to cutting the holes for the tubes
*with regards to the 'templates' once they're perfect I'll print a thicker 3mm part that gets epoxied in.
*28 second boat for the VU. Austria-Hungary Viribus Unitis DN LOA (in) 41.58 Beam (in) 7.5 Max. Wgt. 18.15 Ship Class 4 Units 4 Speed 28 Shafts 4 Rudders 2T It is much easier to get a 10k 550 and gear down from there. Ideally you want 3-4k at the prop and then ESC trim to get it in speed. BattlersConnection has some 550’s that will work. I don’t have the Johnson Motors part number off hand. On my Derf, a 24s boat, I am running dual 10k 550’s 3:1 42p gears 11/33 and the throttle is trimmed to 41% with a 1.5” prop.
This is the same motor that BC sells. Should work fine for a geared drive. Little cheaper here too. https://www.allelectronics.com/item/dcm-462/6-12-vdc-johnson-motor/1.html
Many thanks! The comparisons are very helpful, I'll do alittle research on that, but 10k 550's sounds like a good place to be. I have a pile of Hobbywing 1060 60A ESC's that should be overkill for a low rpm/ high torque 550..
They just arrived, Twas too good to be true.. I'm certain they'll make good bilge pump motors! LOL Played it safe this time, ordered my 550's from Battler Connection You bring up some very good points! Think I'll go with McFadden's Traxxas Villain gearbox to get it on the water. My friction mount can be a side project, don't want it to delay construction Many thanks to everyone for the words of wisdom, I'll get there =)
