Experimenting with brushless out runners and planetary gear reduction units

[SubDude]

Why not print your gearbox, bush the planet gears them with DU bearings. That should run very well in the wet.

I have been thinking more about that lately. Not sure if my CAD skills are up to the task but I won't really know unless I try right? Please pardon my ignorance but what are DU bearings?

[Monahan Steam Models]

Steve,

Could you measure the threaded mounting hole spacing on the face of the motor and let me know the thread size? I could not find those details on Mtroniks website. I’ve been looking at various planetary gearboxes this morning. Did you have a rough idea of what sort of reduction ratio you would prefer?

[Subculture]

Why not print your gearbox, bush the planet gears them with DU bearings. That should run very well in the wet.

[SubDude]

That's a whopper! What's that earmarked for?

Yeah, they are powerful but I run the Mtronicks G2 Hydra 50's in my 66" Nautilus, 1/72nd Columbia and soon to be completed 1/48th USS THRESHER. I like how they perform and run them in the wet. Dialing down the end points helps but it would be better if they had gear reduction of some kind even if I had to custom make something.

[Subculture]

That's a whopper! What's that earmarked for?

[SubDude]

Mtronicks.

[Monahan Steam Models]

I haven’t looked for one for a motor that size yet. If you get a chance, post the motor specs such as shaft diameter, mounting pattern, kv, inrunner or out runner. Or if you have a link to the motor. I will do some research. I’m noticing the robot building crowd uses a lot of brushless motors and planetary gear reduction units. Everything from little stuff to big stuff

[SubDude]

Does anyone make a planetary gear reduction unit that will fit a 40mm dia. motor?

[Monahan Steam Models]

Thank you very much Andy and Gantu for sharing those links.

I will certainly have to take a look at those cells as an option and get an idea for what the energy density is compared to a similar sized LiPo pack. At first glance I’m assuming these are the same types of cells commonly used in back up battery systems for homes and some electric vehicles?

[gantu]

Very good company

https://www.i-tecc.de/shop/einzelzellen/lifepo4/a123/

[Subculture]

Worth looking at LiFeP04 batteries. they have a lower energy density than lipo/li-ion, but are more stable and very long life. The cell voltage is 3.2-3.3v, so 2s gives 6.6v, current capability of the cells linked is 60A, although best to use half that for best longevity- still more than sufficient for model use. e.g.

https://www.ebay.com/sch/i.html?_fro...0-M1B&_sacat=0

[Monahan Steam Models]

Found a 22mm OD 1806 brushless motor built using the same parts as the original 2300kv unit in a 1400kv version.



Ordered a couple and they should be here this week. Planning to swap the shaft and pinion from the 2300kv motor into the 1400kv motor to make them work with the planetary gear reduction. Although the kv rating is still not ideal, it’s better. Also ordered a properly sized 2s LiPo battery pack to replace the 3s pack that I had on hand at the time. This should yield 7.4v * 1400kv / 4.75reduction = 2,181rpm with zero transmitter throw reduction.

Using Andy’s handy formula this brings the speed at full throttle down from 3.6mph (while using a 55% transmitter reduction with the current motor and 3s battery) to 3.3mph running 100% with out any transmitter reduction.

During my research of 22mm planetary gear reduction units I believe I had found the original source who manufactured them. On this site was a detailed complete list of all ratios available in this design. And there was many. Regrettably I did not bookmark the link as now it would be handy to be able to pair a certain kv motor to an available gear reduction unit to arrive at an ideal rpm for a given motor/ reduction combination. I’m still searching to find it again and will post a link when I do.

[Subculture]

Shouldn't be any slack in the belt. A good way to check you have the right tension is to twist the belt, should be able to twist 90 degrees from its normal position, but if you can twist more, it's too slack, much less and you may have it it a bit too tight.

[Schmitty1944]

"Did you have the belts tensioned right? Else the parts must have been moulded in icing sugar or something. Plastic or resin pulleys should be more than up to the job, The most important thing is that they run concentric."

Yes, although to be fair there was a problem with the belt reduction unit before the last fatal run. The pinion pulley was plastic and attached to the brushless motors shaft with a grub screw. The plastic around the grub screw was cracking apart and I made a brass collar around the plastic with a hole in it for the grub screw to keep it all together, At that time I also tensioned the belt, fairly tight with just a little slack. That part held together but after running for a while it was loosing power because the belt was jumping teeth. I do think a belt drive can work. In this case I believe the motor had too much torque for the plastic pinion pulley/sprocket. I suspect it would inevitably fail. Maybe if the speed control featured a soft start would help?

Jason

[Monahan Steam Models]

Nick,

I am Hi-jacking the blog again! Just wanted to show you my new boat build!


Dumas "Lord Nelson Victory"

It's all wood construction 29" with a 10" beam! For my first boat I am going to go electric, and then start saving for a complete tug build with STEAM POWER!

Nick! Thank you for all your advice and help! I am really looking forward to the build!!

Rob
"Firemen can stand the heat"

Rob

That should be a good one to start with.