I just aquired 2 Speed 600 8.4 volt motors, are they good for anything? Perhaps geared on 10 cells? Or what prop/cells could I use DD? Thanks in advance

Cheers

Dale

On 8 cells direct drive something like an 8x4 to 9x6 is a starting point.

Geared 2.3 to 1 something like a 13x8 on 8 cells, or 12x8 on 10 cells will load it up pretty well, but watch temperatures at WOT. Maybe 11x7 is safer. ISTR a 25 sized trainer conversion using more or less that combo in a mag somewhere.

Should pull around 20A or so.

Thats all motiocalc stuff BTW - I haven't used the 8.4V, just the 7.2V. That ran on 7 cells and an 8x4.5 folder DD. Ok but nothing spectacular.

For out and out speed on DD the 7x6 is the prop that was recommended to me.

Thanks for the reply. I plan to run it in a 3.33:1 gearbox on 10 zapped CP1300's turning an APC E 10X10 all crammed into a Model Tech slope Mustang. I dont know what to expect from this setup, will just have to wait and see how it goes. I have all of this stuff currently so that is why I am using it.

Cheers

The Speed 600 8.4v is the most powerful of all the cheapo Graupner can 600's in direct drive mode. As Vintage1 rightly says it works well with an 8x4.5 prop and 8 cells. This is due to the low value for rpm's/volt on this motor meaning it was designed as a slugger.
I replaced the free included no-name 7 cell 540 in my Easy Pigeon by this motor, 8x4.5 prop and 8 cells and the results were very good. Powered gliders of ca. 1250gms are the domain for this motor IMHO.

The Speed 600 8.4v was replaced by the 600 SP which is not quite as powerful as the original. There were faint rumours that the motor was de-tuned due to failures. If true probably the usual case of people grossly overloading them. Mine always ran like an express train and gave no problems.

For geared applications with a cheapo can Speed 600 the 7.2v BB is a better bet as the rpm's/volt are higher. Even with the 7.2v you can safely go to 10 cells in a geared application and get 160 Watts at the prop which is the upper edge of cheapo can 600 performance.

Originally posted by Flint
Thanks for the reply. I plan to run it in a 3.33:1 gearbox on 10 zapped CP1300's turning an APC E 10X10 all crammed into a Model Tech slope Mustang. I dont know what to expect from this setup, will just have to wait and see how it goes. I have all of this stuff currently so that is why I am using it.

Cheers

According to motocalc, that simply won't cut the mustard at all.

A 13x8 is more like it on that ratio and cells or even a 14x10!!

You simply won't load it up enough with the 10x10.


Did you MEAN a 3.33 or a 2.33 box?

Yeah, I thought the 10x10 would be a bit small for the 3.33:1, I do have a 2.33:1 but the shaft is bent slightly, but its still useable, might give that a go.

Chris,

They came with 9x5 props DD, I will give that a go as well.

Cheers

What size plane and weight are we looking at here?

If its small and heavy, DD is the way to go surely?

If this is the plane http://www.angelfire.com/az/rccraze/p51.html then its a hard job to get those motors to work well - needs 300W to really fly, and these are really 200W motors BUT.

Motocalc suggests the 7x6 or 8x4.5 is best on DD & 10 cells, but its very marginal. 9x5 was in overheat terrotory. It will be fast tho.

On the 3.33:1 I checked out the APC E range and 15x10 came out the best.

On 2.33:1 the 12x8 seemed good.

However none of these had the top speed of the 7x6 direct. If climb is what you want the geared stuff will be good, but top speed will be maybe 45 mph, whereas the DD won't give the climb but might take the speed up over 60mph.

Its the model below. I have had a MM on 8 cells DD with an 8X4 in the past and that was more than enough power, unfortunately the MM is now dead and since the 2 speed 600's were free I thought I'd chuck one one in. Ok, I might go with the 8X4 DD on 10 cells then and then try the 9X5 on 8 cells.

Cheers



Specifications:
Wingspan: 50 in
Wing Area: 428 sq in
Length: 37 in
Flying Weight: 2 lbs Empty Radio Required: 2 Channel

Ah. Thats a lot lighter than the reference I found, and bigger too.

Still on DD its not got a lot of climb potential, you are trading that for out and out speed.

I'd say the best compromise is the 2.3:1 sort of box, and the 11x8.5
on ten cells. Although 10x7 to 12x8 all looked reasonable. Depending on whather you wanted speed or climbout.

Its been interesting working out whats happening. On DD you have a maybe 60mph plane that hardly climbs at all, on the 12x8 geared it climbs fast, but has a level top speed of maybe 40mph.

Your choice Should be great whichever way.

I'l let you know how it goes either way (if the wind ever dies down). By the way, the whole purpose of re-powering this glider is to test my new pedal launcher, it worked great when it was just a glider but now I want to see if my bungee is strong enough when the model is heaver.

Cheers

I finally got around to testing the Mustang with the Speed 600 8.4V on 10 CP1300's turning a Graupner 8X4 Slim Prop. The pedal launcher worked well although I did not do the best flying on the launch, was a bit off track but all was ok. The power was great and the duration was also good at around 4 minutes to BEC cut off. Thanks for all of the replies.

Cheers