HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Apr 24, 2001, 12:42 AM
What's a Member??
Sydney,Australia
Joined Mar 2000
632 Posts
What should I do with a Graupner 480???

My dad has just come back from Germany and brought along a Graupner 7.2v s480 BB Race NO.6327
Specs are:
Nom. voltage 7.2
voltage rang 4.8-8.4
No load speed 27 000 RPM
Current drain at max efficiency 8.5 A
Max. effic 78% (without Gearbox)

Now, what should I do with it? Can I use it as a replacement for my DD s400 planes for more ooomph?? Or are the RPM's too high wich might necessitate the use of a gearbox? If I use it in dd what kinda prop should I use and what kinda batts would be good. Would 600AE handle this motor or are they too weak?

Thanks Alex
Regecide is offline Find More Posts by Regecide
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 24, 2001, 09:07 AM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
Put it in a a MF480, and find a lightweight model (gnat?) to go with it.
..a
Andy W is offline Find More Posts by Andy W
Reply With Quote
Old Apr 24, 2001, 09:24 AM
Registered User
Gordon's Avatar
Joined Aug 2000
3,920 Posts
Take advice on the max current to use for longevity - probably about 12A or so.

At the currents used in EDF, ie about 20-25A on 10 cells, these motors don't last long before the commutator burns.

Gordon

Gordon is offline Find More Posts by Gordon
Reply With Quote
Old Apr 24, 2001, 09:52 AM
Registered User
Jurgen Heilig's Avatar
53859 Niederkassel, Germany
Joined Sep 2000
18,765 Posts
What was the plan when your dad bought the motor? I would probably use it to power a Cosmotech 4.5:1 gearbox. Jurgen

[This message has been edited by Jurgen Heilig (edited 04-24-2001).]
Jurgen Heilig is offline Find More Posts by Jurgen Heilig
Reply With Quote
Old Apr 24, 2001, 11:45 AM
Super Senior Member
Albuquerque, NM
Joined Feb 2000
3,396 Posts
Give it to me
Slope Nut is offline Find More Posts by Slope Nut
Reply With Quote
Old Apr 24, 2001, 06:29 PM
What's a Member??
Sydney,Australia
Joined Mar 2000
632 Posts
Hey Nut, I'd rather keep it
I wasn't really looking at an EDF plane more at a sport/pylon plane, if I find a good gearbox that will fit it I will replace a s400 4:1 gearbox in a homemade sailplane. Would it be possible to just use another pinion, but still use the same graupner 4:1 inline gearbox or do i have to use a seperate one??
If I were to use it in a DD application I would have to up the cells to at least 800AR right? If I would use the GB could I still use the 600AE's. I was at teh LHS a while ago and I spotteds some 600SCR's, they were little red stumpy but fat cells. They should be able to handle the current up to about 20 amps shouldn't they? How big are 800AR's?? I've never seen anybody use them at teh local field.
Thanks for your help guys.
Oh yeah, 20 amps for a 6X3 sounds like a damn lot. What about if I use a 4.7X4.7 prop for a pylon type model, that should bring the amps down abit shouldn't it??
Regecide is offline Find More Posts by Regecide
Reply With Quote
Old Apr 25, 2001, 01:24 AM
Registered User
Bristol, England
Joined Aug 2000
2,077 Posts
From experiece, if you keep it down to about 7 cells and keep the load down to no more than 6x3, you are looking at around 20 amps and over 16 000 revs. The brushes will then last for a (normal!) season. I would suggest minimum of 800AR cells.

Use? Pico Jet Combat works well with it.

Regards to all, John
John E is offline Find More Posts by John E
Reply With Quote
Old Apr 29, 2001, 05:37 AM
What's a Member??
Sydney,Australia
Joined Mar 2000
632 Posts
Anyone??
Regecide is offline Find More Posts by Regecide
Reply With Quote
Old Apr 29, 2001, 05:00 PM
Registered User
Bristol, England
Joined Aug 2000
2,077 Posts
OK, I'll help.

We found the 6x3 to be about optimum in the PJC, and when we went down to around 5x3, the thrust went down, and current draw went down to about 18 amps, so we were getting shorter flights through having to keep the power on.

The cells that I have seen marked 800AR are AA shape but a little fatter, and around 30 grams. The slightly lighter 1300 NiMh did survive with this motor (well cooled!), and they are about 8oz for 8 cells.

I guess you could expect lower current drain with a pylon racer when it is moving.

Unfortunately, I have never seen 500s or 600s, so I wouldn't like to comment.

Good luck, John

John E is offline Find More Posts by John E
Reply With Quote
Old Apr 30, 2001, 12:38 AM
Registered User
Keithw's Avatar
Auckland New Zealand
Joined Mar 2001
386 Posts
Quote:
Originally posted by Regecide:
if I find a good gearbox that will fit it I will replace a s400 4:1 gearbox in a homemade sailplane. Would it be possible to just use another pinion, but still use the same graupner 4:1 inline gearbox or do i have to use a seperate one??

unlikely- it has a 1/8 shaft, which is larger than s400 2.5mm or whatever
the pinions are most likely not large enough in diameter to have the extra hole size in the middle- it also means you are probably looking at a s500/600 sized gear reduction.
If you want speed, you want direct drive


If I were to use it in a DD application I would have to up the cells to at least 800AR right?

probably- thats what i use, but i stay with 6 cells rather than going to 7.


If I would use the GB could I still use the 600AE's.

depends on the current you get down too. in my experience 600AE won't give you more than about 15amp without damaging them


20 amps for a 6X3 sounds like a damn lot. What about if I use a 4.7X4.7 prop for a pylon type model, that should bring the amps down abit shouldn't it??
These are high reving motors, & high current consumption
On a 4.7 cam prop i was drawing 17-18 amps on 7x800AR in my pylon. when the 4.7 broke on landing i put on a 5x5- the current was more like 25 amps.
Reducing to 6 x 800AR cells gets it back to a reasonable 16-17 amps- reasonable speed , but also duration- enough to finish the race.
stay below 20 amps for both the motors & batteries sake. if you want to use 600AE reduce the cell count to stay below about 15 amps.
at these currents you need larger capacity batteries hence 800AR-
500 & 600 give such short flight times it's hardly worth it.
I have some 1400 NiMH cells doubled up (parallel) so i have 2800 mAh at 20 amps or more (the small 1400 NiMH can only deliver 10-12 amps before the voltage sags heaps)so i get 7 -8 minute flights.

unfortunately- due to the weight of the motor & of the bigger cells you need, your wing loading goes up, so a small wing may not give you enough lift to make it an easy flier.


[This message has been edited by Keithw (edited 04-29-2001).]
Keithw is offline Find More Posts by Keithw
Reply With Quote
Old Apr 30, 2001, 02:34 AM
Registered User
Bristol, England
Joined Aug 2000
2,077 Posts
Keith,

That's interesting about the use of 6 800AR. We tried it on 6 subCs, and the motor went better than on the 8 NiMh, so it really does benefit from the lower resistance cells.

Regards, John
John E is offline Find More Posts by John E
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
What should I do with my Hummingbird Electronics? Manchild Micro Helis 6 May 30, 2003 12:48 AM
Question 850mah L-ions Surplus - What should I do with them? Draconious Batteries and Chargers 8 Feb 21, 2003 07:20 PM
Help me Decide what I should do with Hobby-Lobby order... SmoothSL Electric Plane Talk 7 Oct 22, 2002 10:46 PM
What should I do with 7.2 volt speed 400 motors. erashby Electric Plane Talk 7 Sep 27, 2001 02:24 PM
What should I do with my old RC equipment??? atsiang Electric Plane Talk 15 Jun 22, 2001 01:05 AM