Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Mach1]

I have two ROXY C42-50-06 800kv that were intended to go into a 1/12th scale lifeboat but this may now not happen.
Would it be possible or difficult to install these into a single screw large tug by somehow coupling them together with a gearbox that would limit the speed of the motors ? They description of these motors says they are high torque.

[mogurnda]

It would be much easier to fit a single large brushed electric  motor than to run 2 outrunner brushless motors through a gearbox.   

David

[Mach1]

Yes that’s exactly what I thought. I will forget the idea.  Many thanks for your reply.

[JimG]

Probably no need to go to a big brushed motor, just use one of the brushless. With a kV rating of 800 it should turn a good sized prop. Need to limit the speed of the motor then either use a transmitter which allows you to change the end point of the throttle stick or just reduce the voltage of the battery, a 6V  will give you off load revs of 2400 and 12V 4800 revs off load.
Jim

[Taranis]

Surely you meant 800rpm per volt Jim? 6x800 = 4800 etc


I agree one motor is plenty for a tug and I would use a Hobbywing Quicrun car ESC as they are so appropriate in my experience.

[Mach1]

Thank you very much for the advice it is much appreciated.

[Adam]

It is quite possible to drive a tugboat via a gearbox with a brushless motor

[Mach1]

Thanks Adam, I will give this some thought.

[Taranis]

Why use a gearbox? No need
https://techno.smugmug.com/Billing-Boats-Hoga-tug-708/i-wkGDHN4

[Adam]

Thanks Adam, I will give this some thought.

I tried to add some pictures of my Kolga with brushless motor, but somehow I couldn't ad pictures to the post, but now it works....
 

[derekwarner]

Hi Adam.......this is certainly an impressive helical speed reducer 


1. I am not quite sure of the box material construction, but it appears to be substantial wall thickness
2. Is the motor secured through those front 4 x holes?
3. What type of lubrication are you using?.......flooded?
4. Do you hear any thrust noise at higher speeds?


In gearing, only one thing better than a single helical, is Herringbone, or double reversed helical


Derek

[RST]

Hi Derek I was thinking similar things earlier and maybe falsely concluded it was an MDF type material but maybe not.  But of note it's a delight to see a lovejoy coupling that small and I'd use them if a source that small was readily available.  I think I made out the use the well-known gear company HPC according to the stamps on the gears, I'll have a check for couplings there as I've not seen lovejoy couplings that small before.


Rich

[derekwarner]

I too hadn't seen Renold Spider type couplings in small size ranges either Rich, but yes HPC have them from 3mm to 16mm bore .....the RED flexible element is probably a Polyurathane which for model applications should last 10 x lifetimes


Derek

[RST]

I too hadn't seen Renold Spider type couplings in small size ranges either Rich, but yes HPC have them from 3mm to 16mm bore .....the RED flexible element is probably a Polyurathane which for model applications should last 10 x lifetimes


Derek

Yea, I deliberately didn't use the word "spider" to see if anyone else knew them as "lovejoys".  Perhaps it's semantics or trade names but to be honest the "spider" part to me was more the rubber / polymer bit in-between.  When I used or needed to order them them in industry (not many times) as you say the composition and shore hardness etc was critical, but on a model I always thought these were ideal if they were small and cheap enough.  I know Robbe or Graupner tried a variant of these for a while, perhaps they were just too expensive to keep the product line going for small volume orders.

[Subculture]

https://www.ebay.co.uk/itm/174589666259?hash=item28a65ae3d3:g:3tIAAOSwrv1gBOc-

[Martin (Admin)]

 
Wow, very nice!

[Dave_S.]

Please excuse my ignorance, but with the easy availability of cheap but powerful brushless motors at various kvs, surely it is more efficient to choose a motor of low kv and cut out the complexity and potential losses as a result of using gearboxes? I would go for a big beefy outrunner with low kv to suit the prop and use batteries of the required voltage.


I am more than happy to be told why I am wrong, it's the best way to learn!

[derekwarner]

Dave ...I certainly have little knowledge of electrical matters, but am sure if the application was a land based model  [with unlimited electrical supply constraints] then the use of additional drive train elements could be considered as unnecessary in the grand scheme of output rotation

One of the main uses of speed reducers in engineering application drives is to allow the prime mover to function at its preferred or optimal operating range, be this speed, energy consumption, or torque related...

There are certainly efficiency related considerations with any additional element in the drive, however in a well engineered solution, these inefficiencies are accepted as necessary to achieve the total drive output 

I have not seen any 'current draw vs load' specification listings from the manufacturers of these newer brushless motors 

Having said this, one cannot but acknowledge the apparent engineering quality of well sized ZZ sealed ball bearings, high performance and cost-effectiveness of these little 3 phase motors over the older design, bushed, brushed motors, and all with the knowledge that you will not damage or burn out your brushless motor ....as those very expensive $$$ multi amp speed controllers appear to act as very effective quick blowing  fuses


My main point of earlier comment [and compliment] was the use of helical gearing over noisy & rattle-ee  straight cut spur gears

Derek

[derekwarner]

Just for interest, and for a better understanding of what others do, I looked at Ocean-Works ..[this manufacture of model azimuth marine drives has attracted excellent reviews here on MBM...so I consider a good reference]

Z-Peller Azimuth Thruster (Z-Drive) Propulsion Combo set 60mm

This is a brushless motor for an Azimuth propulsion unit and it uses a 5:1 geared speed reduction between motor & drive shaft [propeller] their 75 mm diameter azimuth drive also uses a 5:1 reduction ratio

Other alternate brushless motor belt driven azimuth units in the Ocean-Works garage appear to be 4:1 speed reduction

I acknowledge this is certainly not comparing apples with apples, however is interesting


Derek

[marco]

Bonjour ,


   On my tug I use brushless 300 Kv under 12 volts , reduced to 3:1 and they work well . The assembly is personal .


    https://youtu.be/jdrdOZ_13FA
   

[Martin (Admin)]

Please excuse my ignorance, but with the easy availability of cheap but powerful brushless motors at various kvs, surely it is more efficient to choose a motor of low kv and cut out the complexity and potential losses as a result of using gearboxes? I would go for a big beefy outrunner with low kv to suit the prop and use batteries of the required voltage.

I am more than happy to be told why I am wrong, it's the best way to learn!

Just thinking out loud, could it be that Brushless motors have low starting torque or low rev performance?   
 

 
 

[Subculture]

If they're sensorless then starting torque is lower than sensored, but with current esc's this is barely an issue, especially for boats, as a propeller is a fluid clutch.

For prop sizes up to 2.5-3" diameter, direct drive is straightforward beyond that it's possible but the choice of suitable motors narrows and the price rises significantly. therefore a single reduction stage, with gears or belt is often desirable.

[Dave_S.]

For prop sizes up to 2.5-3" diameter, direct drive is straightforward beyond that it's possible but the choice of suitable motors narrows and the price rises significantly. therefore a single reduction stage, with gears or belt is often desirable.

That makes sense, thank you - coming from a model aircraft background, everything in model boating seems cheap! Even the 4258 500kv motor I bought for my Crash Tender was under £100 delivered, complete with 120A ESC.

[Adam]

1. I am not quite sure of the box material construction, but it appears to be substantial wall thickness
2. Is the motor secured through those front 4 x holes?
3. What type of lubrication are you using?.......flooded?
4. Do you hear any thrust noise at higher speeds?
In gearing, only one thing better than a single helical, is Herringbone, or double reversed helical

1. Gearbox material is Brass 2mm CNC milled.
2. Yes they are.
3. Planned is something like Gear grease EP0, but because everthing is still underconstruction, I haven no usere experiance with these type of grease.
4. The test run only took place without (with very little) grease and an open gearbox lid.
But the noise level was not too bad for me. Obviously more than a timing belt gear, but not disturbing.All shafts are equipped with seals, so if all is well the grease should remain in the gearbox...

I don't think herringbone gears are aviable in these small module.

[Adam]

I'll have a check for couplings there as I've not seen lovejoy couplings that small before.

https://nl.aliexpress.com/item/32761192525.html?spm=a2g0s.9042311.0.0.27424c4du1fQbH