Anyone have experience with Graupner Brushless motors?

[Bob Gato]

Nice motor Tom! and IP67 on the ESC- great...Are you going wet with either the ESC or Motor?

[Stephen Vick]

It will work If one has the screws turning outboard Thrust cancels out and side force takes over. According to Crenshaw’s Naval Shiphandling. Anyway that’s how I set up my 1/32 Type II and it works , also a 1/40 Type XXI and it works Atlanta Class cruiser , Fletcher Destroyer on and on I love twin screw differential throttles. You see I was a QM1 in the Navy. When you throw away the thrust , side force does the job. The boat will twist in its own length I guarantee.

[Stephen Vick]

I looked at the Engle motors when I ordered my bayonet rings. However Graupner had a Black Friday sale and I got them for $15 each.

[trout]

Bob, in the dry.

$15!!! Wow....too bad payday is too far away and I have other commitments with my money.

[Bob Gato]

I'm under the understanding that graupner has just been purchased by a South Korean company and it's going through an economic reorganization and they've stopped production for an indefinite time... What's on sale I think is on sale until the stock runs out

[Stephen Vick]

That is too sad I was floored when Robbe tanked, now Graupner goes down.

[Subculture]

They were purchased by the Asian company some time ago, it's the German factory that is being shut down. So production goes on, but solely in the far east. There's little market in kits these days, the business is all in RTR's or ARTR's, and that requires cheap labour to make it profitable.

[Bob Gato]

[QUOTE=trout;n135434]Bob, in the dry.

You know , I never hear about anyone complaining about a dry running outrunner overheating in a sub (They rely primarily on air for cooling) -it must not be a problem-possibly the intermittent operation and very little flank running.

[trout]

Bob,
I also think (scary I know) the cold water cools the air in the tube.

[Subculture]

Watt for watt, brushless motors will produce a bit less heat than their brushed counterparts, as you have no friction generated from brushes and commutator. The difference is going to be minimal at lower power levels however.

Most model motors tend to have efficiencies of around 60-80%, which means about 20% of the power you put in is lost to resistance in the windings and friction. Clearly if your boat is using say 10-20 watts, it's nothing much to worry about, but if you're pushing 100 watts or more, you need to start thinking about some additional cooling- this would apply to any electric motor brushless or brushed.

A lot of marine modellers seem to equate brushless with power, well they can certainly deliver that, but do you need it? If not size the motor a bit more carefully, a brushless motor of equivalent performance to a brushed motor will be much smaller in size.

The 28mm outrunner motor on the left here offers twice the performance of the speed 400/380 on the right, yet takes up much less space, with no nasty electrical sparking to compromise your radio and costs about four pounds. It can spin a 27mm prop direct drive at around 21000RPM, suitably geared it can swing much larger props, and has sufficient power (about 100watts) to propel most model submarines unless very large. I use these with 20A rated controllers.

[Stephen Vick]

I wanted to try brushless because of the higher efficiency and low current draw. Plus it’s new and kinda cool I just couldn’t find one which wasn’t stupid fast. Until now

[Subculture]

Easy enough to find motors of smallish size that go down to around 300kv. Much below that the motors tend to get bigger, or they just lack power, plus they tend to become inefficient as the windings become very dense and you get electrical losses.

So for best efficiency I would consider a single stage reduction if you need below say 250kv. Low KV outrunners are popular with multirotor flyers swinging large props, as they need a lot of static thrust, so that's a good place to look.

The low kv outrunners do tend to be a bit more expensive than the higher kv. So for instance, decent 28mm outrunners in the 1000kv range are available for around the £3-4 range direct from China, with reversible esc's vailable for around the £12 mark, so for about fifteen quid you can have a brushless set-up.

A lower kv outrunner can cost £12-30 depending on where you get it. so can double or triple the cost. Course if you want to swing a big prop, a 28mm 1000kv will struggle for any prop over 50mm/2" of pitch. Therefore you may consider some reduction. GT2 pulleys and belts are cheap on ebay, because they're made in huge quantities and give a silent and efficient method of reduction. However the pullets often require bushing to fit smaller shafts, so a lathe is handy if you have access to one.