Graupner 500E 12V

[Peter NordsjoeParticipant @peternordsjoe33686]

Hello again guys,

I am looking at using a dual motor setup on my 1:24  70ft Vosper MTB. I want to go with a 12V set up and while surfing for possible motors I stumbled upon the 500E (specs below). Does this seem sensible? If so what kind of propsize am I looking at. Could I use a single ESC?

Graupner Speed 500E (1788)

Economy 540 size motor with low current drain.

GRAUPNER SPEED electric motors are equally well suited for model planes, boats and car applications. The nominal operating voltage is in each case marked on the motor case for ease of identification.

Specification:
Nominal voltage 12 V
Operating voltage range 6 … 12 V
No-load rpm 12000
No-load current drain 0,4 A
Current drain at max. efficiency 2 A
Current drain when stalled 10 A
Max. efficiency without gearbox 67 %
Length of case, excl. shaft 50 mm
Diameter 35,8 mm
Free shaft length 8,5 mm
Shaft diameter 3,17 mm
Weight 158 g

Thanks in advance!

Regards,

Pete

[60wattParticipant @60watt]

Hello Peter.

I built a 72 foot vosper mtb at 1:24 with 2×540 motors but needed every ounce of power I could get.

I no longer have that model but there is a photo of it taken after it was seaworthy in my gallery.

I ran 6 volt 540 motors off  a Yuasa NP2.6-12 and limited the duty cycle to 60% and got the model to a fast cruise for 3 minutes as the battery was only 2.6 amphour capacity.

From the data you supplied,all you can get out of your two Graupner motors is 30 watt each at 6000 rpm and at ~50% efficiency.Your prop will have to be smaler than scale and at a shallow pitch.I used two small Graupner plastic props painted bronze.I’ll look out the part number to give you an idea as I was running at 6000 rpm

Technology has moved on so if I repeated that project I would now use high capacity hydride or Lithium batteries and save weight wherever possible.

Tom

[Peter NordsjoeParticipant @peternordsjoe33686]

Thanks Mr. Watt but sounds like you think two 500Es might not quite cut the mustard. Previously I have been recommended to use a single 600 Eco (also Graupner). I would have thought it would be plenty to use 2 x 500 size motors.

A thought on these so called "Eco" motors. If they run on less juice and give less Watts, at the end of the day are they not just a small motor masquerading as a big motor???   

I was think of using a SLA 2,4 Ah 12V  ca 0.9 kg. A bit on the heavy side for sure but still relatively cheap to come by. Think it is a bad idea? Also will the choice of ESC be affected by the type of battery used? I ask because I have seen ESCs with the word "lipo" smacked into it indicating (to me) it is for use with Lipo batteries.

Thanks Pete

[60wattParticipant @60watt]

Hi Peter.

My battery was 200 gram heavier and I would have saved on build weight if I knew it was important before I started construction.I had no such problem at 32nd scale.It sat very low with a 6v 4 Ah Pb battery but it managed to skim on calm water for longer than my attention span.

I don’t know if the power requirement goes through the roof if an mtb hull is greater than 3 feet or whether the power,weight issue is just tricky at 3 feet.

Two 540 sized motors managed to get the boat cruising.

In theory, a single brushless motor running at 60 watt output and 75% efficiency would save on weight and on power.That would save the weight of one motor but youl’d need to make a gear drive if you stuck with two shafts.

The unfortunate fact of small brushed motors is that you will only get 50% efficiency at a reasonable power output.

Tom

[Peter NordsjoeParticipant @peternordsjoe33686]

The need to use two shafts come of the fact that I want to make the two rudders hanging on the outside of the transom as scale as possible. There is a rudder inside the hull down the centerline but I would like to use that space for some other gadgetry (very hush hush you understand ) So with two working rudders on the sides I recon it won’t turn so well with a single prop in the center. 

Do you know anything about belt drives? Thought that would be quite a cool solution as opposed to regular gear drive.

[60wattParticipant @60watt]

I used twin screws to avoid the turning circle problem of my smaller single screw model.

I don’t think anything would be obtained by belt drive other than as a method to drive twin screws by one motor.I managed to achieve higher power by using 6 volt motors and at the same power figure you would achieve with those Graupner motors.Simple arithmetic from 60 watt at 50% efficiency shows you like me won’t get more than a few minutes out a 12-2.6.My model wasn’t especially heavy either.

If you show me me what hush-hush stuff you have by a pm or email then I’ll do likewise.

Tom

[Peter NordsjoeParticipant @peternordsjoe33686]

I think I will go with a big motor with belt drives. Just seems cooler some how.

Well the hush hush is more about fear of having a harebrained idea. I want to try and make a serious smoke screen generator using  fans, a metalbox and smoke cartridges normally used for airflow studies and checking ventilation systems. See http://www.bjornax.se/engelsk/en_index.htm and then click on "smoke cartridges" to see some films, (check the color ones since the white one looks small and puny.) I know you can fire them up remotely as they are used on electric are planes to create smoke trails. Probably just heat from resistance.

Pete

[Peter NordsjoeParticipant @peternordsjoe33686]

Enough ompffh?

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