Experimenting with brushless out runners and planetary gear reduction units

[Monahan Steam Models]

Gathered up a couple different size brushless out runner motors and a couple planetary gear boxes to play around with and couple together. The idea was to use slightly higher kv rated motors with gear a reduction to slow the final output rpm down and gain some more torque while reducing amp draw and gain finer low speed rpm control. Here’s what just about bolted together off the shelf with only some miner modifications.



Here’s a 22mm OD planetary gear unit bolted up to 22mm OD brushless out runner. The gear unit is normally found attached to 180 size brushed motors. This unit came as a 2 stage gear reduction at 22:1



By removing one of the two planetary gear sets and chucking the gear case in the lathe to face turn off 4mm of material, I was able to convert the unit to a single stage reduction at 4.75:1



After machining



Reassembled. Very smooth to turn over.



Made a bigger brother version too. The bigger version use a 36mm OD brushless crawler motor and a 3:1 planetary gear unit intended for use with 540 size brushed motors I found on Amazon.

Both combinations spin around 3500 rpm at 7.4 volts and at 11.1 volts the smaller unit turns about 5,370 rpm’s and the larger unit about 5,180 rpm’s. Both have a ton of torque through the rpm ranges at either 7.4 or 11.1 volts. The gear units with the brushless motors allow for much finer final rpm control especially down low and I’m guessing a lower amp consumption spinning larger propellers. That part I still want to test once I get a decent wattage meter.

Nick

[SubDude]

Very interesting Nick. Definitely watching. Where did you get the gear boxes?

[Subculture]

The cheapest way is usually to look for used geared motors on ebay. Not all are planetary boxes though.

Another solution would be to print some gears, you usually only need s single stage of reduction, and with printing you can use some complex profiles like a herringbone pattern which will be both quieter and stronger than straight cut gears.

I prefer toothed belts and pulleys for the odd occasion a reduction is required, as they're silent and almost maintenance free. GT2 belts and pulleys (used extensively on FDM printers) are very cheap on ebay, you can even print the pulleys if you wish, but I think the aluminium pulleys are worth the little extra cost. The finished set-up isn't as compact as a gearbox.

[Monahan Steam Models]

Very interesting Nick. Definitely watching. Where did you get the gear boxes?

Thanks Steve

I found the larger 36mm diameter planetary gear unit on Amazon here: https://www.amazon.com/gp/aw/d/B083S...b_b_asin_title

The larger gear unit is okay in quality. It doesn’t come lubed with with grease and the outer ball bearing easily falls out of the output shaft housing. Not a big deal as grease is easily added and a drop of lock-tite on the bearing will hold it in place.

The smaller 22mm gear unit and motor here: https://rectifiedrobotics.com/produc...tary-gearmotor

The 22mm gear unit I noticed is very commonly used across a number of other products offered by various suppliers. It’s very precisely made and runs extremely smooth. It’s also very quiet.

I’ve found that a lot of gear unit originally intended for use with brushed motors share the same mounting hole spacing and fastener sizing as brushless motors that were made to be almost drop in replacements for their brushed counterparts.


Nick

[Monahan Steam Models]

The cheapest way is usually to look for used geared motors on ebay. Not all are planetary boxes though.

Another solution would be to print some gears, you usually only need s single stage of reduction, and with printing you can use some complex profiles like a herringbone pattern which will be both quieter and stronger than straight cut gears.

I prefer toothed belts and pulleys for the odd occasion a reduction is required, as they're silent and almost maintenance free. GT2 belts and pulleys (used extensively on FDM printers) are very cheap on ebay, you can even print the pulleys if you wish, but I think the aluminium pulleys are worth the little extra cost. The finished set-up isn't as compact as a gearbox.

Andy,

Great info as always. I also like using toothed belts and pulleys when a gear reduction is required for the same reasons that you have pointed out.

A benefit of a single stage planetary gear unit is they offer a very compact and robust solution. When these units are manufactured to a high level of precision, they often run very quietly. Since the orbital gears around the motor’s pinion gear are being evenly loaded there is less side loading of the motor’s output shaft.

The biggest reason I have recently been experimenting with these combinations is due to a complete equipment refit of a small tug boat I’m working on currently. This tug was actually the very first wooden model boat I ever built and really was my start in the model boat and submarine hobby over 32 years ago. Over that time, this boat has had many different types of running gear systems in it. The first being a simple steam unit. The following being a few different electric propulsion systems. I was about to convert it back to steam as I custom built a very small precision steam engine and gas fired boiler specifically for it some years ago.

Most of the electric components fitted into the boat over the years were often too big or too heavy or over powered. But that was the components available at the time. The boat was gutted of all equipment and put on the shelf as a display for the last 25 years until now.



Here she is now, exactly as she was when I built her 32 years ago. I was 12 at the time. It’s a Midwest products “Harbor” tug. The boat is only 25” long with a 7 1/4” beam. Hull is balsa and bass wood construction that was glassed over before paint.



A current look inside the hull today shows the aftermath of many different propulsion installations over its career.


With how small components have gotten in today’s world, it will be night a day easier to refit this model with a modern running gear. In fact the space will be mostly empty compared to jam packed in the past. For this refit in particular, the compact inline advantage of a small brushless out runner paired with a single stage planetary reduction unit will keep the weight down low in the hull and allow ample room to access the LiPo batteries and what ever other gear that may be added.




The one off scratch built steam engine and boiler combination I made for this tug in 2009 when I planned to refit her back to steam back then.

Nick

[SubDude]

That steam engine is off the charts amazing! Does it run?

[Monahan Steam Models]

That steam engine is off the charts amazing! Does it run?

Thanks! Yes sir it does. The bee twin oscillator engine is self starting and fully proportional in forward and reverse. It has a water pump on it also for keeping the water level in the boiler topped up during operation. The boiler is a horizontal water tube type boiler that is gas fired with a butane/propane mix. Boiler operates at up to 80psi and was hydraulically pressure tested at 180psi when it was certified and serial numbered.

[rwtdiver]

Andy,

Great info as always. I also like using toothed belts and pulleys when a gear reduction is required for the same reasons that you have pointed out.

A benefit of a single stage planetary gear unit is they offer a very compact and robust solution. When these units are manufactured to a high level of precision, they often run very quietly. Since the orbital gears around the motor’s pinion gear are being evenly loaded there is less side loading of the motor’s output shaft.

The biggest reason I have recently been experimenting with these combinations is due to a complete equipment refit of a small tug boat I’m working on currently. This tug was actually the very first wooden model boat I ever built and really was my start in the model boat and submarine hobby over 32 years ago. Over that time, this boat has had many different types of running gear systems in it. The first being a simple steam unit. The following being a few different electric propulsion systems. I was about to convert it back to steam as I custom built a very small precision steam engine and gas fired boiler specifically for it some years ago.

Most of the electric components fitted into the boat over the years were often too big or too heavy or over powered. But that was the components available at the time. The boat was gutted of all equipment and put on the shelf as a display for the last 25 years until now.



Here she is now, exactly as she was when I built her 32 years ago. I was 12 at the time. It’s a Midwest products “Harbor” tug. The boat is only 25” long with a 7 1/4” beam. Hull is balsa and bass wood construction that was glassed over before paint.



A current look inside the hull today shows the aftermath of many different propulsion installations over its career.


With how small components have gotten in today’s world, it will be night a day easier to refit this model with a modern running gear. In fact the space will be mostly empty compared to jam packed in the past. For this refit in particular, the compact inline advantage of a small brushless out runner paired with a single stage planetary reduction unit will keep the weight down low in the hull and allow ample room to access the LiPo batteries and what ever other gear that may be added.




The one off scratch built steam engine and boiler combination I made for this tug in 2009 when I planned to refit her back to steam back then.

Nick

Nick,

My wife spotted this "Steam Engine" of yours again, and she is giving me the eye! I would just love to build a nice steam boat! I am still looking at the (Alexandra) it is still the one I really like. After seeing your steam engine again, going electric would be sin for sure!

I also looked at the Carol Moran, which is similar to the Monahan!?

Rob
"Firemen can stand the heat"

[rwtdiver]

Nick,

Beings you got the Tug Boats and Steam Engines making there way back in! (which is great) Would you mind answering a question for me as to what Boat Kit manufacture you would recommend! I have looked at Krick, Dumas, and Turk Models! They all three have some what looks like really nice kits in the $300.00 range!

Sorry to take us off tract again here, and Nick I do appreciate your expertise with building and running steam and electric boats! Thank you for your advice!!

Rob
"Firemen can stand the heat"

[Monahan Steam Models]

Rob,

Krick and Dumas I am both familiar with and they’re both offer good kits. I’ve never heard of Turk models so I can not comment about them. I’m a sucker for old all wood plank on frame kits. I enjoy the process of building the hull bit by bit and the unforgivingness of making each piece fit together like it was born there with out using filler, regardless if I’m covering it in paint or a clear coat. But that’s me.

Steam can be complicated and challenging very much like building a submarine. Best advice I can give you is stick with a simple steam engine system like I have advised before. Something like the vee twin oscillating motor like the one I built and pictured above in this thread.

Usually open boats such as steam launches make a good subject for steam as they are open and everything is readily accessible.

Tugs also make for good steam powered models but with the added hassle of needing to remove and install the superstructure. With a steam launch you can quickly and easily read the steam pressure gauge on the boiler and water level in the sight glass while running the model. With an enclosed model like a tug or something similar, this is much more difficult and you’ll need to run your boat enough to get an idea how long the water will last before needing to bring it back to shore.

Boiler feed water pumps can extend run times but this adds a lot of complexity and I would always strongly advise against adding all the bells and whistles for someone just starting out in the steam hobby.

As far as refitting my old tug with the steam plant I purpose built for it, yes it would be neat to use and easy to make it happen but I already have a small personal navy of steam powered boats. One more or one less at this point wouldn’t make much of a difference. I have plenty of open style steam boat projects in various stages of completion to tickle that interest.

I should also mention open boats like steam launches show off the equipment better than closed boats. Part of the neat thing about steam is seeing the goods running as you’re sailing it. I have plenty of closed hull boats that are steam powered and sure the mechanical sound of the engine resonating in the hull is neat to hear as well as seeing the plume of steam being released out of the stack as it sails by, but you can’t see the jewelry running inside. Just my two cents.

Nick

[rwtdiver]

Rob,

Krick and Dumas I am both familiar with and they’re both offer good kits. I’ve never heard of Turk models so I can not comment about them. I’m a sucker for old all wood plank on frame kits. I enjoy the process of building the hull bit by bit and the unforgivingness of making each piece fit together like it was born there with out using filler, regardless if I’m covering it in paint or a clear coat. But that’s me.

Steam can be complicated and challenging very much like building a submarine. Best advice I can give you is stick with a simple steam engine system like I have advised before. Something like the vee twin oscillating motor like the one I built and pictured above in this thread.

Usually open boats such as steam launches make a good subject for steam as they are open and everything is readily accessible.

Tugs also make for good steam powered models but with the added hassle of needing to remove and install the superstructure. With a steam launch you can quickly and easily read the steam pressure gauge on the boiler and water level in the sight glass while running the model. With an enclosed model like a tug or something similar, this is much more difficult and you’ll need to run your boat enough to get an idea how long the water will last before needing to bring it back to shore.

Boiler feed water pumps can extend run times but this adds a lot of complexity and I would always strongly advise against adding all the bells and whistles for someone just starting out in the steam hobby.

As far as refitting my old tug with the steam plant I purpose built for it, yes it would be neat to use and easy to make it happen but I already have a small personal navy of steam powered boats. One more or one less at this point wouldn’t make much of a difference. I have plenty of open style steam boat projects in various stages of completion to tickle that interest.

I should also mention open boats like steam launches show off the equipment better than closed boats. Part of the neat thing about steam is seeing the goods running as you’re sailing it. I have plenty of closed hull boats that are steam powered and sure the mechanical sound of the engine resonating in the hull is neat to hear as well as seeing the plume of steam being released out of the stack as it sails by, but you can’t see the jewelry running inside. Just my two cents.

Nick

Thank you Nick!

Appreciate you taking the time to give me this great information! I will most likely go electric with the first Tug, and save up some money for a good quality steam system on the next one! I would like to start out with a good quality total wood boat for my first build! Thanks again!

Rob
"Firemen can stand the heat"

[Sinksalot]

Why not just use low KV motor. Like 300 to 500KV. They have tons of torq and run good at low speeds.

[Subculture]

Reduction is worthwhile for subs with prop sizes around 63-75mm (2.5-3") diameter or larger, or where fitting a big motor is impractical or inefficient. For most model subs direct drive is absolutely fine.

[Monahan Steam Models]

Why not just use low KV motor. Like 300 to 500KV. They have tons of torq and run good at low speeds.

Yup, that’s exactly what I did with the 1/48 type VII build and going to be doing on with a type XXIII build. The prop size and pitch on those boats compared to the motor size are perfectly fine running direct drive with low kv motors like you point out. I’ve so far used a set of 350kv and 500kv motors with great results.

Like Andy has pointed out, adding reduction can help in a situation where spinning a larger prop relative to the motor size can be beneficial as just one example.

Unfortunately there are not as many low kv motors available to chose from in various size ranges when compared to the higher kv motors. Direct drive with a properly matched brushless motor works great in most applications such as airplanes, drones, and high performance boats as well as certain scale boat applications. For myself, I’ve found the need to add reduction when I’ve wanted more torque and low rpm control for a particular build. Especially in a scale rock crawling rig but also in scale boat and submarine builds.

Until now, I’ve never attempted to use an off the shelf planetary gear reduction unit with a brushless motor. Just sharing this experiment here to see how well it works out and what combos are easily paired together while getting input from others.

[Subculture]

Sunnysky motors worth a look for low KV. lots of poles too, so very smooth running at low RPM.

https://sunnyskyusa.com/collections/v-motors