Going Brushless?

This links up a few threads on this:

https://www.theassociationofmodelsubmariners.com/t1017-going-brushless#8786

I had an interesting chat with the "Man on the Stand"  at SHG Model Supplies at Blackpool this weekend.

He confirmed the growing use of brushless motors in model boats and mentioned the following useful information relevant to model subs:

- Multi-pole, outrunner motors are the ones to go for (high torque and relatively low rpm (measured by rpm per volt)

- Be careful selecting ESCs if you want reverse to work well. Outrunner motors driving large props have large inertia and so ESCs need a good brake circuit. He recommended the Mtroniks ones.

-They will send a motor selection chart if you email them.( I will do this and give a link if it is suitable.)

On another topic I was interested to see that SHG offer toothed timing belts. (Very nice reduction gear for drives - much quieter.) They are often hard to find.

Just another snippet of information.

When using outrunner brushless motors, to match the torque the diameter of the motor should be about the same as the prop diameter. (Source: Ian, A club member at Barrow who uses brushless.)

I see that an article in the latest model boats (Winter Special Edition, 2014) says that the motor should be 2/3rds of the prop diameter.

So take your pick. Both are for use with direct drive, fast electrics.

Also deciphering the numbers on a brushless. Not too easy because different manufacturers use different systems but usually:

4 numbers - the first two are the motor (can) diameter and the second two the can length. If you are lucky their will be another group of numbers which may be the rpm per volt figure.

e.g Himark C3526-830 is a 35mm diameter motor 26mm long which will give 830 rpm per volt (Source: Model Boats Winter Special edition 2014)

(Note that nothing is given about power output. They often have a glow plug engine equivalent which shows who the major users are!)

I have just had some phone feedback this morning from Graham B over in Cornwall.

He started this brushless query off, in fact.

He says that this combination works very nicely in his 4 foot long dynamic diver- a very lively performer. (he has promised photos.):

Hobbywing Ezrun 3656 Brushless combo (truck type ESC included) Easily available on eBay .

e.g

http://www.ebay.co.uk/itm/Hobbywing-Ezrun-3656-RC-car-brushless-motor-120A-Waterproof-SC8-ESC-Combo-4700kv-/261036027662?pt=UK_ToysGames_RadioControlled_JN&hash=item3cc6f5af0e

It directly drives a 1 1/4 prop (32 mm) (So the ratio of motor diameter to prop diameter is 0.9)

Thanks Graham.

http://www.vintagemodelboats.com/page13.html

Brushless motor £10

matching esc  £25,  £30 with cooling fan

Other sizes available

Even though I'm at the bottom of a brushless learning curve, Couldn't resist it at that price so I bought a set at the Blackpool show to try in a Skipjack
(project no 4 in line so a revue/build log will be a while in coming)

John

My contribution to the trials:



I have chosen the Mtroniks combo because in my view:

- It is easily available from a  major supplier.
- The ESC is OK for reverse and is waterproof!
- The motor is an outrunner and is only 1000kV so I hope will be slow and torqy.
- Not TOO expensive at £60.
- The whole thing is lovely and small (about 1/3 of the brushed motor volume.)

http://www.mtroniks.net/prod/Boat-Speed-Controls/G2-Hydra15-System.htm

It works well on the bench with good proportional control and easy setup. You can see that I'm working on a 3:1 reduction using toothed timing belts (My favourite drive system and you can also see an M8 brass bolt getting in there!) It is going to go into my Turkish Nordenfelt which is smooth and sharp and 1m long. It also has a very large prop - it was a steam submarine.

I will report back when I get to try it out in the water at Barrow within the next few weeks.

Some light reading for anyone interested in Brushless Motors

From Southern soaring Club - southafrica  2005 Author Brian Mulder


http://www.southernsoaringclub.org.z...-motors-1.html

http://www.southernsoaringclub.org.z...-motors-2.html

http://www.southernsoaringclub.org.z...-motors-3.html

http://www.southernsoaringclub.org.z...-motors-4.html

http://www.southernsoaringclub.org.z...-motors-5.html

It should take your mind off all that Turkey and Plum Duff.....

Best wishes to everyone

John

I can't get these links to work, John!

Nigel has also commented on my lack of bearings in the photo. This was the early "lash-up" to get the belt tension right. My later version (photos soon) has a ball race set into the brass nut just under the larger pulley.

David

Apologies for non working links...  (cut and paste ???)

try

http://www.southernsoaringclub.org.za/

and click on ARTICLES

and also schematics & software at

http://ww1.microchip.com/downloads/en/appnotes/00857a.pdf

Thanks John!

Very interesting articles (particulary if you want to DIY motors - increasingly unlikely in future, I think, with commercial availability.)

The theory also shows just how critical the electronics are. (And of course no mention of reverse in the article - not much needed for aircraft!)

David

As promised, some details of the Mtroniks Hydra trials in My Nordenfelt sub.

These were taken last Sunday at Barrow in Furness MBC (11/1/2015).

I am using an 11v Lipo battery in this and she is running a large prop with a 3:1 reduction. The sub is 41 inches long and is very streamlined.

The videos show plenty (too much at times) of power but controllable. This all comes from a very small space (see the photo) I have the option of a using an 8v Lipo which I will trial later.

Fortunately (after I stopped taking photos!) I tried dynamic diving and stuck it in the mud for a worrying 3 minutes. So plenty of power for dynamic diving! I also had some problems with power cut offs later on. This looks like problems with the internal BEC. I have had this often with brushed ESCs and I will try a separate BEC.

But overall I am a convert to brushless. Even for the space saving alone they are worth having. (As Dr Schmidt says.)

The Mtroniks Hydra combo seems fine.

I will try some "bucket trials" soon to get some idea of current draw.









https://youtu.be/iF8zgMTQxnA

https://youtu.be/YOR8cqpv8RQ

https://youtu.be/_2PSn9yudhU

Even on  a freezing day, I could not resist including some shots of Dave J and his VERY impressive petrol power boat (he has to the dark side gone!) Now with new electronic ignition (Santa Claus?):








https://youtu.be/22z-yWn7b-k

https://youtu.be/EwziPWbnIMM

https://youtu.be/3CsPsqOJ1KQ

+ the Red Peril. (Fortunately we are still allowed to use IC engines on our pond.)

Some feedback from the "Bucket Tests" and my latest test on the now brushless Nordenfelt at Barrow this Sunday.

The Mtroniks Hydra combination with that prop configuration running in a water filled bucket gave the following current draws at full speed:

3 cell lipo (about 12v) 2.7 amps

2 cell lipo (about 8v)  2.1 amps.

Both of these are OK but I chose to use the 2 cell lipo for the test at Barrow.

It all went well. Good scale speed. Good battery life. No problems with the BEC (I think BECs give problems at the higher battery voltages (12v). No problems so far with wear on the (Simrit) shaft seal.

So that is about it. I am now very much "sold" on brushless motors in model subs! Thanks for the information everyone.

David

I thought it would be useful to give a review of my experiences using brushless motors over the past season.

I now have them installed in 4 subs (Holland, Resurgam and the 2 Nordenfelts. The last 3 share the same WTC.)

The motors and 2 controllers have been well behaved and reliable. I haven't experienced any problems with shaft seals although the revs are kept down because these are outrunners and I reduce them by 3 to 1.

Significant advantages are:

- space saving as Andreas said originally.

- more efficient - hard to estimate but run times are good.

- good smooth control - you can use this to limit the maximum revs and so prevent your sub taking off if you catch the sticks! (See later sub rescue article!)

- Loads of torque for large, scale type props.

- Plenty of power. No need to engage in trial and error or dubious calculations to estimate motor size. The supplied motor worked well with my models ranging form 0.5 to 1.5 m long. (The 1.5 m one is the Russian Nordenfelt - see the videos at Norwich 2015.)

- Cheap replacement motors. The Turnigy Aerodrive D2830/11 1000kv motors can be obtained for about £7 each from Hobbyking. (I also see that the Hydra Controllers from Mtroniks are getting cheaper.)

I will keep some subs running with the original brushed motors but the next job for the new season is to replace the 2 thirsty brushed motors in my type XX1 with 2 of the Turnigy brushless.

David,

do you have any photos of the shaft seals you are using?

i see photos of the motor and belt drive, but none of the "outside" areas.

thanks

Tim

Hi Tim,

I use oil seals (Simrit is the manufacturer). I have found them very good and they last for years.

My approach is shown in this thread from 2011 with a photo about 3 postings down. (The idea originally comes from Norbert Bruggens book "Model Submarine Technology.)

https://www.theassociationofmodelsubmariners.com/t266-prop-shaft-seals

It is not very sophisticated but it works well for me. I would think any lip type oil seal with a spring tensioner built into it would work. It runs on a 4mm shaft. (All my shafts and control rods are 4mm diameter. Makes things easier.)

David

I did the first trials of twin Mtroniks Hydra motors and ESC combinations in my (considerably) revamped Darnell type XXI this Sunday. (You can see more about this boat in the build logs - Darnell Type XXI - Graham's Dad's U boat)

The props are 3 bladed about 2 inches in diameter and are run with a toothed drive belt,  3 to 1 reduction like my other subs. (5 of my subs are now brushless.)

The type XXI went very well at a good high speed (It is a type XXI after all!) The Darnell XXI is about 60 inches long.

For the first time I was able to use telemetry (Thanks Tim S !) to measure current draw while underway. 3.5 amps total at 12 volts flat out and 2.5 amps at a more reasonable cruise. I didn't notice any significant increase in temperature inside the WTC. (This brushless setup is now practical with a 4 ah lead acid battery. The previous brushed motors were much thirstier but I had no way of measuring current.)

I had to add 700g of lead ballast to compensate for the weight of the old brushed motors. Brushless motors weigh nothing by comparison - another bonus.

I've found this Mtroniks combination to work very well and I now have 2 of their ESCs and 4 motors in my subs (all bought with my own money.) The last 3 motors were bought from Hobbyking - cheaper as described earlier in this thread.

It is good to be able to have a "standard" drive system across the whole fleet!

Later edit. A couple of photos taken today in lovely weather and with a newly extended (flooded!) pond at Barrow:

And some videos taken last Sunday in a rather flooded Barrow lake (you can hear my welly boots splashing!)  but a beautiful sunny day:

The 3rd one shows a complete static dive cycle (single home made piston tank (proportional control from openLRS system))

Flat out drawing about 3.5 amps:

https://youtu.be/M6ig24kj5BM

https://youtu.be/SKtJYzQWV8c

This shows a complete static dive cycle (single home made piston tank (proportional control from openLRS system)) One or two lost packet beeps.

https://youtu.be/eJctgegvn5U

Hi David.

The XXI is looking and performing great.

Has the leak in the pond been fixed now?

John

Thank you!

I think the honest answer is we don't know because we have had so much rain over the last few months.

If we get a hot dry summer (here's hoping!) we may run into problems again.

David

Just a follow up on the brushless saga. I am very pleased with my "all-brushless" fleet and I don't think I will use brushed from now on. Brushless "tick all the boxes", in my view.

It is also nice to report on very good after sales service from Mtronik.

One of my three Hydra 15 speed controllers had developed a fault. (No reverse). It was well over a year old but they replaced it free of charge with no fuss.

(Please note that I have no other commercial interests with Mtronik other than as a "cash paying" customer.)

David

Hi David,

I strongly believe there is no need to gear your propulsion when using BL motors, you can use them as direct drive. I did in my our old vintage boats WR.

The trick is to use:

• Outrunner motors, they have more torque than inrunner motors
  

• Use motors with low kv (rpm/V) they have more stators so more torque.
  

For example:

• I use a tigny outrunner motor dimentions dia 28 x 36mm, 750kv to propel a 800mm tugboat witha 4 bladed propeller dia 45mm.
  With a 7.4V 4000mA lipo we can sail for more than one hour.
  

• The same motor but a 950kv version I use to propel a robbe PT15 with a high speed propeller of 35mm, same battery. I can fly her over the water for more than one hour, no sweat at all and she is fast.
  

Grtz,
Bart

That's an interesting observation, Bart.

Dropping the 3 to 1 gearing would make things even simpler and add another "tick" in favour of brushless motors.

The motors I use are outrunners and are 1000kV.

I used gearing partly because I was worried about wear on the "Simrit" shaft seals. (This doesn't actually seem to be a problem.)

I really like the increased efficiency (and so battery endurance) with brushless. The Type XX1 used to last for only about 20 minutes with brushed motors with a 12v 4aH lead acid battery. Now it lasts for an hour and more with twin brushless and the same battery. (Mind you, I think now that I can monitor amps using Tim Senecals Telemetry I keep my "foot off the gas" rather more!)

One problem with brushless is that they have too much "ooomph!" I managed to sink my Holland last year when I caught the throttle stick and managed to ram the sub into the mud on the bottom of our pond! (I got it back after locating it with a Pinger, fortunately.)

David

the high end brushless speed controls are now very programmable as well. i use castle creations ESCs for pretty much everything now. you can find side-winder micros which will handle all our needs for sensorless brushless outrunners for $60 or less, and they have all sorts of settings that can be altered. including maximum speed. on several of my subs, max speed is limited to as little as 30% of true max speed (reverse can be set separately, so you could go with 30% max forward, and 10% max reverse). so in david's case of having an outrunner that is 1000kv, it is like magically converting that to a 300kv motor. simple math becomes possible. say you know that your propeller needs to be 3500rpm for good scale speed, but your system is 2s lipo, and you motor is 1200kv... well raw speed for the motor is 8800rpm, so 39% is what you want. For sensored in-runners, there is now the castle creations micro X, at roughly $80, which has all the same programability.

Thks Tim, I use LRP ESC's in my cars and they (the high end ones) have the same function.

Grtz,
Bart

Just a little point about Mtronik brushless EScs.

I had a recent problem with two of them connected via a Y lead.

I seemed to have an intermittent problem with them both switching on to reverse only.

After examination, I found that I had forgotten to disconnect the red positive lead to one of the ESCs. (I use a separate switch-mode power supply for the RX)

Making sure that both were disconnected meant that again I got forward and reverse.

I also note on doing an RTFM (Read The Flaming Manual!) that it is best to switch the TX reversing function to Normal when doing the setup.

So my 3 Mtronik ESCs are still performing well after several years.

David