600 motor power output

[Chris Salomon]

This has gone way off topic but the odd thing is I'm really interested because I have two ED Racers that I used to use in C/L planes as a kid!

[Erfolg]

In some respects it is off topic, yet the core sentiments are being observed.

• We all like to make use of our model equipment, however old
• Some modelling equipment has a technological shelve life, Reed RC, Deisel engines, Treasured Dunlop/Pirelli Rubber etc.
• Technology and expectations move on, with time.

In this respect the 600 has little place in a modern electric aircraft. We all like from time to time dabble in nostalga.

Myself, I  have built an electric Vic Smeed Tomboy, brushless with Lipo. You can verbally paint an image of breathless summer evenings , or lazy hot days with puffy clouds slowly drifting overhead. The reality the wind is frequently at approx. 15mph. It is not steady. Worst of all, we expect our models to do circuits, simple arobatics. The model was not conceived or designed to do these things, so by to days standards, copes, but not well.

So it is with the 600.  It is the equivalent of the vintage car. If you want cheap, comfortable, and predictable performance in a car you buy a Ford etc. Do not buy a Austin 7 and think it will do 200 miles on the motorway at 70 mph consistantly.

Many brushed morors were pushed hard, well above 7 cells to get a performance. Many modellers saw the motors as a consumable and would grudingly live with a short life. At that time to charge above 7 cells needed an upmarket charger, hence cost. It was these limitations which made electric flight the province of the dedicated or bloody minded.

Put the 600 in a box and gloat over it from time to time (that is what I seem to do), reject the strictures from the wife to dump that junk in the bin, as you never use it.  But under no circumstances be tempted to use it, you will only be disapointed, or construct elaborate images of what a pleasure it is to struggle for height, the smell of overheated shellac, the romantic grind of gearboxes, the black dust from tortured brushes.

Still have an unopen Mole Technology Gearbox for a 600. Such a level of workmanship, crap by todays standards.

Erfolg

[Mike Rolls]

I did quite a bit of testing of 600 size motors about 4-5 years ago, but mostly in belt drive set-ups as direct drive was so clearly offering poor performance. There were a couple I recorded on DD, however.

Both on 8 cells 2400 and spinning 9x5 Graupner CAM props:

Graupner Sp 600 8.4V -                 27A    221W input  9,200RPM

Hurrinca 650 (Overlander)            28A     202W input  9,000RPM

In each case the battery pack would have been fresh off charge. As you can seem the comments about a 600 offering aroud 180W or so aren't far off - the amps I was pulling would probably not have led to very long brush life for those motors.

Mike

[Tim Mackey]

Claimed best current draw for a speed 600 is around 12A but the actual stalled current figure is 80A !!

maximum expected efficiency is 62%

[Erfolg]

Timbo

I think think you are being very fair (as normal, except when pulling my leg). If we operate within prudent limits

taking 15 amp and 9.6v we get 144w

now take an efficiecy of 65% we get 94w

now feed this through our gearbox at 90% we arrive at 84w.

The 90% efficiency is probably generous, based on tooth losses through meshing(2-5% per mesh), assuming an involute gear form (one that is rotational contact, rather than sliding), friction losses due to shafts on bearing housings, and churning (generally low on models, as little lubrication is provided)/windage. A poor gearbox will eat power, possibly as low as 50% efficiency.

These figures indicate why I crucified my motors, heated the batteries and looked for the next motor to buy.

They also indicate why the improvement in efficiency from a larger swept area was so desperatly needed, and why the results from gearing could disappoint, if the gearbox was not good enough or we tried to pull to high acurrent for to long.

Also tells you why my cheap outrunners (plain bearing no ball bearings etc.)  easily outperform the best brushed set up.

Erfolg

[Tim Mackey]

Yep agree entirely Erfolg - brushes are for floors

[Steve Hargreaves - Moderator]

Just picking up on the ED Racer with a throttle bit (even though it is way off topic I know ) Brian Winch detailed a conversion in RCM&E a short while back whereby he fitted an OS10 carb to an ED Racer (modified the backplate venturi to take the carb spigot) & apparently it worked very well....no exhaust chopper needed.......

[Guest]

thanks steve,

 I will look it up - I think I have an ancient os10 lurking about somewhere

John