I am looking at geared 7mm pager motors with a lot of
thrust and power.
My choices seem to be (both with 1.7 ohm blue/purple motors):

A. GWJ: http://www.bsdmicrorc.com/index.php?productID=625

B. Plantraco's GB07: http://www.microflight.com/Online-Ca...s/GB07-Gearbox

I am wondering:
I. if one can use these in a pusher mode
(I fly in small areas and want to protect the motor and prop)

II. how easy is it to replace a motor on one of these gearboxes?
In particular, where can one get a new pinion gear for the new motor,
or if one uses the old pinion, how does one handle any slippage from using an old pinion (thread locker?).

=====================
I am also looking for general comments on these 2 gearboxes.
As far as I know: both are ~4g for motor and gearbox

A. the GWJ: has ball bearings, a plastic pinion, a 4:1 gear ratio,
a prop adaptor, a 1.5mm prop shaft (stronger, can handle more prop adaptors for GWS props),
is more expensive (US$27)

B. the GB07: probably does not have ball bearings, looks like a metal pinion,
a 5:1 gear ratio, no prop adaptor, a 1.0 mm prop shaft (lighter, fewer prop adaptors for GWS props available),
is less expensive (12.99 US$?, CA$?)

Thanks.

What about using a Snap & Fly 7mm motor with one of those gear boxes? It seems to be a pretty "hot" motor.

There's also this one, at U$$ 8. I've been meaning to order one to try for some time, but I've been busy with other projects to add more to the stuff-to-be-used-someday box to collect dust.

I've been meaning to order a couple to play with too. But every time they were in stock the other stuff I wantesd wasn't. So I backordered em anyway.

Don'ty know how accurate those thrust figures would be tho.
bill

Originally Posted by scrubs

I've been meaning to order a couple to play with too. But every time they were in stock the other stuff I wantesd wasn't. So I backordered em anyway.

Don'ty know how accurate those thrust figures would be tho.
bill

I have the above mentioned $8 gearboxes. The ones I have run smoothly. I can't measure the thrust but this might help. The gearbox ratio is 4:1 and the motor resistance is 1.4ohms. If you look at Gordon Johnson's motor tests (http://home.comcast.net/~gordon-johnson/ss7mm.htm last table) you see he tested the 4:1 BSD gearbox with a 5030 prop and the blue SS motor (~1.6ohm) and got about 29.2g of thrust at 3.5V. Their test shows 31g at 3.3V with a hotter wound motor. Unless I missed something those figures may be fairly accurate.

Daniel.

To Brent Slensker: thanks for the pointer to the Snap & Fly 7mm motor.
They may be "hot", but I do not know if they will fit in a gearbox
(which I would need to generate more thrust).
I also would need to buy one to test it, as I have no data on it
(for the others, I can use the Gordon Johnson url mentioned below for
data).

To AleG: thanks for the pointer. I should have realized that Hobby King would have a version.

Originally Posted by DONGO

I have the above mentioned $8 gearboxes. The ones I have run smoothly. I can't measure the thrust but this might help. The gearbox ratio is 4:1 and the motor resistance is 1.4ohms. If you look at Gordon Johnson's motor tests (http://home.comcast.net/~gordon-johnson/ss7mm.htm last table) you see he tested the 4:1 BSD gearbox with a 5030 prop and the blue SS motor (~1.6ohm) and got about 29.2g of thrust at 3.5V. Their test shows 31g at 3.3V with a hotter wound motor. Unless I missed something those figures may be fairly accurate.

Daniel.

Two complications that may make those figures less accurate for the $8 gearbox:
A. The BSD gearbox has ball bearings, but I am not sure if the $8 gearbox does or not (my guess is not as ball bearings are often the most expensive part of a gearbox, at least with GWS gearboxes).

B. One of the 2 reviews in http://www.hobbycity.com/hobbyking/s...Gearbox_GPS-7#

mentions:
"Certified Buyer Rated 3 crowns 1/24/2010
cbrian4 |

Does not produce the specified thrust, on a gws 4530 prop at max throttle only produces 20 grams."

=============================
Anybody have experience swapping motors with such gearboxes
or using such gearboxes in pusher mode?

Originally Posted by flying-llama

To Brent Slensker: thanks for the pointer to the Snap & Fly 7mm motor.
They may be "hot", but I do not know if they will fit in a gearbox
(which I would need to generate more thrust).
I also would need to buy one to test it, as I have no data on it
(for the others, I can use the Gordon Johnson url mentioned below for
data).

To AleG: thanks for the pointer. I should have realized that Hobby King would have a version.


Two complications that may make those figures less accurate for the $8 gearbox:
A. The BSD gearbox has ball bearings, but I am not sure if the $8 gearbox does or not (my guess is not as ball bearings are often the most expensive part of a gearbox, at least with GWS gearboxes).

B. One of the 2 reviews in http://www.hobbycity.com/hobbyking/s...Gearbox_GPS-7#

mentions:
"Certified Buyer Rated 3 crowns 1/24/2010
cbrian4 |

Does not produce the specified thrust, on a gws 4530 prop at max throttle only produces 20 grams."

=============================
Anybody have experience swapping motors with such gearboxes
or using such gearboxes in pusher mode?

The $8 gearbox does have ball bearings. As for the thrust I was just trying to make a educated guess. I would image if you swap the motor for a SS it should perform closer to the BSD gearbox. Of course you then have to add the additional cost of the motor to it. I have mine in a parkzone cessna with a blue SS motor, I think a 4030 prop (I will check it later and edit to correct). I can cruise around at about 60-70% throttle once the battery has been discharged some. It can also loop. As for pusher mode I don't really know.

Daniel

Originally Posted by DONGO

The $8 gearbox does have ball bearings. ...

Good to know.

Originally Posted by DONGO

... As for the thrust I was just trying to make a educated guess. ...

Understood.
As might be evident from my replies, I have been making my own share
of guessing.

Originally Posted by DONGO

... I would image if you swap the motor for a SS it should perform closer to the BSD gearbox. ...

My guess is that both use the same type of inexpensive pager motors
and that the differences are mainly in the gearboxes.

Thanks.

A note on that 7mm brushed gearbox from Hobby King:
http://www.hobbycity.com/hobbyking/s..._Gearbox_GPS-7

It turns out that this system is discussed in this thread:
http://www.rcgroups.com/forums/showthread.php?t=996615

Post #22 of this thread mentions that the prop shaft is really soft.
This thread also talks about the CO3 gearbox for a brushless motor.
From the pictures, the CO3 gearbox itself and the gearbox for the 7mm motor by itself look
pretty similar (and post #26 mentions that the C03 gearbox will fit a 7mm motor).
The CO3 gearbox itself appears to have a soft prop shaft and other
prop shaft issues.
Some of these are discussed in the Hobby King entry for a combination with CO3
(under BOTH "Discussion" and "Reviews"):
http://www.hobbycity.com/hobbycity/s...Product=10003#

This thread talks about replacing the CO3 prop shaft with a stronger shaft:
http://www.rcgroups.com/forums/showthread.php?t=1103751