HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 23, 2003, 08:17 AM
Registered User
Dave Wulff's Avatar
USA, FL, Fort Lauderdale
Joined Feb 2002
1,902 Posts
Mike,

I am surprised to see that the HV M20 from Kenway is a full ohm higher than the HV from ToyTronix. The jump from 1.5 to 2.5 ohms makes for quite a different motor. Does anyone know if the difference from 2.5 to 3.5 will be linear as compared to the first two?

Dave
Dave Wulff is offline Find More Posts by Dave Wulff
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 23, 2003, 05:35 PM
Registered User
Columbus, OH USA
Joined Jun 2003
14 Posts
Gordon,
Do you have testing data on the Mabuchi K10 or GWS version(smaller brother to the M20). Are these available surplus?

Thanks,
Bill
bpaar is offline Find More Posts by bpaar
Reply With Quote
Old Jul 24, 2003, 05:12 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Bill,
The problem is the K10 and K20 like high volts. Even higher than 5 volts if possible. Ralph Bradley has had some success with a K20 (GWS 05) direct drive with a voltage booster. However, to me it is looking like certain of the pager motors (like a Didel 6x15mm 10 ohm) will be better than the K10 in terms of thrust to weight. And, the Didel pagers are readily available and moderately priced.

The K10 GWS version can only be obtained by gutting a Pico servo. The Mabuchi has a less hot wind and cannot be obtained surplus that I've found. The GWS version of the K20 can be obtained in their "05" propulsion set. It's also longer and heavier than the K10.

I'm still working on tests of the smaller motors and they are pretty incomplete at this point.

Gordon
Gordon Johnson is offline Find More Posts by Gordon Johnson
Last edited by Gordon Johnson; Jul 24, 2003 at 09:15 AM.
Reply With Quote
Old Jul 24, 2003, 08:23 PM
Registered User
Columbus, OH USA
Joined Jun 2003
14 Posts
Thanks Gordon, I will wait for one of my pico servos to die...

For my current project, I need ~15 - 18g of thrust using 1 LiPoly cell with a weight of 3.5g (motor, gearbox and prop). I am testing 2 different 7mm pagers now. I have read they are very reliable and I can come close to the weight goal. The 7mm Namiki looks promising.

Bill
bpaar is offline Find More Posts by bpaar
Reply With Quote
Old Jul 24, 2003, 09:17 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Bill,
That will be tough. Can you use a large prop, or is it a more scale plane that needs a smaller prop? A 7mm pager weighs ~2.7g. A 6.7:1 gearbox with Didel gears runs ~0.7g. So, under these assumptions you have about 0.1g left for a prop. It's really difficult to do with these smaller motors unless you go for a relatively larger prop and higher gear ratio to get the thrust you need with that weight. Coincidentally, I'm about to test a 7mm pager. I'd suggest you test at 3.5 and 5.0 volts and then consider one of Graham's voltage boosters.

Gordon
Gordon Johnson is offline Find More Posts by Gordon Johnson
Reply With Quote
Old Jul 25, 2003, 05:13 AM
Registered User
Columbus, OH USA
Joined Jun 2003
14 Posts
Gordon,
I will use a large prop, and gear it high.

The Didel 7mm pager is 2.8g, my 9:1 gearbox is 0.7g and wes prop 0.9g. I will also try 16:1 and 20:1 ratios. With some work I could get it down to ~4g at best. I haven't received the Namiki motors yet, they are supposed to be ~2.2g (I will let you know, sounds too good).

I have not tried 6mm pagers or BitChar-G yet, other threads seem to indicate that these motors are not consistant. I may have no other choice to make the weight goal .

Bill
bpaar is offline Find More Posts by bpaar
Reply With Quote
Old Jul 25, 2003, 11:33 AM
Registered User
mars's Avatar
San Francisco, CA
Joined Jan 2002
577 Posts
Related question...

Can I draw 1200mA out of a 145 or will I fry it?

I am trying to fly a Funcraft P-51 on a Bob Selman m20 w/ what I thini is a 4.4:1 ratio.

Thank You,

Mars
mars is offline Find More Posts by mars
Reply With Quote
Old Jul 25, 2003, 12:17 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
You should probably do that in short bursts, or possibly not at all if you are concerned about the life of your cell. That is about 8.3C and the rule of thumb for the 145 is about 7C. I pull 7C out of my Kokam 145's routinely, but pretty much in short bursts.


A better choice for sustained operation at that level would be to use the DWE 170mAh cell. It's only slightly heavier, but the extra capacity means you would be pulling 7C out of it. If you intend to do that for extended periods you could always go up in capacity to either the DWE 230 or the ET 250 and you would only be pulling in the 5C range, although at a heavier weight.

Gordon
Gordon Johnson is offline Find More Posts by Gordon Johnson
Last edited by Gordon Johnson; Jul 25, 2003 at 12:19 PM.
Reply With Quote
Old Jul 25, 2003, 03:05 PM
Registered User
bmutlugil's Avatar
Turkey
Joined May 2002
2,178 Posts
Or maybe wait until we get the 145 mAh sizes of the 20C Kokam LiPoly's sold by FMA Direct (maybe others too). In this case you should be able to go up to 2.9 Amperes.

It is still hard to beleive this will come through, though. Must be the ideal battery.. If they could decrease charging time, too..

Best regards,

Bulent
bmutlugil is online now Find More Posts by bmutlugil
Reply With Quote
Old Jul 25, 2003, 03:41 PM
www.bphobbies.com
cybermike's Avatar
Lincroft, NJ
Joined Feb 2003
132 Posts
Or the new E-tec 210mah cell which is about .8 g lighter than the 250 and can take the 1+ amp of a KP-00, though too soon to say for how many cycles (I can say positively at least 3 cycles ). The DWE 170mah will definitely do it continuously - but only for "a while" until it starts to loose it's oomph.

Me - I'm just waiting for that 2g fuel cell that will put out 10+ amps indefinitely Give it a year or two...

Mars - I finally flew the Kenway 4.2:1 box with the M20-LV (KP-00 motor) last nite with a GWS 4 x 2.5 prop. Wow! Suddenly 3D for a micro doesn't seem out of the question...

Mike C.
cybermike is offline Find More Posts by cybermike
Reply With Quote
Old Jul 30, 2003, 10:33 AM
Registered User
mars's Avatar
San Francisco, CA
Joined Jan 2002
577 Posts
Thanks for the info cybermike.

Is the 4x2.5 a prop with a large diameter hole in it? if so, how do you attach the GWS prop to the shaft?

Thanks,

Mars
mars is offline Find More Posts by mars
Reply With Quote
Old Jul 30, 2003, 10:50 AM
www.bphobbies.com
cybermike's Avatar
Lincroft, NJ
Joined Feb 2003
132 Posts
Mars - I reamed it out just a tad so it fit nice & snug over the main output gear. So far it hasn't fallen off the couple of times I've flown it, even after a "controlled flight into house" incident

The only drawback is it makes for a tight fit in a scale plane - had to put a big hole in the front bulkhead of J3 Cub to get enough clearance.

BTW-a three bladed K&P folding prop also seems to work pretty well (on a bench test), and will fit over the shaft with just a tad of reaming. Haven't flown that combo yet though.

Mike C.
cybermike is offline Find More Posts by cybermike
Reply With Quote
Old Jul 30, 2003, 11:03 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
GWS makes rubber prop adapter inserts. If you put one of them in that prop you should be able to then put a screw through it into the Kenway gear. It may take a small amount of drilling/reaming of the rubber insert to get it the right size for the screw. BTW, the rubber insert adds a bit of weight.

Another alternative is aluminum adapters. A couple of years ago I had BMC Model products make me a few up. Or, if you know someone with a lathe it would be pretty simple to make. Again it adds weight.

Gordon
Gordon Johnson is offline Find More Posts by Gordon Johnson
Last edited by Gordon Johnson; Jul 30, 2003 at 11:07 AM.
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
hacker 20 motor mount and prop mount Jack Hyde Power Systems 5 Oct 23, 2005 05:44 PM
Motor Prop Test Results! tallflyer GWS (Grand Wing Servo) 0 May 07, 2004 10:52 AM
I need help determining motor/gearbox/prop for sailplane Chris K Electric Plane Talk 5 May 01, 2002 09:29 PM
MG-1 motor/gearbox/prop kit nip + GWS Props Al P Aircraft - Electric - Airplanes (FS/W) 1 Jan 06, 2002 12:56 PM
Motor/GearBox/Prop question.... NickBee Electric Plane Talk 3 May 04, 2001 09:02 AM