DIY IR LRFers - Page 3 - RC Groups
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Aug 27, 2003, 11:29 AM
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Graham, Gordon

Thanks for the tips, compliments.
Might just get the weight down to 1g.
This helps to keep model down to target weight, which I might just be able to meet. Need to lighten remote actuator and pushrod next.

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Aug 27, 2003, 03:34 PM
in persuit of low wing loading
Gordon Johnson's Avatar
What is the diameter on your CF push rod? I generally find I can get by with 0.5mm rod, which weighs next to nothing. Nice job on your actuator.

Aug 27, 2003, 06:24 PM
Registered User

The pushrod is about 0.85mm, far to big. Being only 50mm long 0.3mm might be plenty big enought. Can't get .3 cf here though, will have to split some .5 rod.

Aug 27, 2003, 06:40 PM
in persuit of low wing loading
Gordon Johnson's Avatar
I generally use the 0.3mm rod on room flyers, and where the length isn't too much. so, you are probably ok.

Check with Dave Lewis. The 0.3mm rod is so flexible that he might be able to roll it up into a padded envelope and mail it to you air mail, which would probably cost about $2.00 from the US. That might be easier than splitting some.

Aug 28, 2003, 02:51 AM
Registered User
I have a couple of questions.

Prop for my LRF. I had planed to use the 4mm x 8mm 10ohm motor, 25:1, M.3 gears. I have carved a prop from balsa, GWS 114mm copy. GWS 1.4g, balsa copy without hub 0.2g. Not sure of pitch as I had previously scratched it off. Looks like it might be the 114 x 120. Pitch might be ok, but to long maybe?

Constant current output for IRLML2502?

Just looking at my new pcb layout, thought I should check current rating of some of tracks, make sure they can carry load. Batt- to mosfet source I think is the only one. Could solder GND link to mosfet instead of top of board.
Copper on pcb is about 0.04mm thick. If I calculate area and compare to wire sizing chart in actuator coils/bobbin style thread will this be about right?


Last edited by david_dewit; Aug 28, 2003 at 03:20 AM.
Aug 28, 2003, 04:47 AM
Sticky Shepherd
Graham Stabler's Avatar
Unless your tracks are super thin don't worry too much. The lengths are so short that any voltage dropped will be small.

Aug 28, 2003, 08:34 AM
Registered User
Just remembered where I saw info on the IRLML2502 mosfet.
Plenty enough for most if not all IR applications.
Aug 28, 2003, 06:51 PM
Registered User
I thought it was made clear at the begining of this thread that this DIY IR is Koichi's Tanaka's excellent work.

I thought since I was making one I would post some pictures and try to fill in some of the gaps and bring some of information together so it could be more easily found for other people wanting to do the same. So people wanting to make one didn't have to go through the exspence and trouble of re-developing.

At no time was I trying to take credit for Koichi's work.
My opologies if I have misled or offended anyone.

Full credit goes to Koichi Tanaka

Again, I thank him for the help he has given me.

Aug 28, 2003, 08:43 PM
Registered User
I also would like to thank Koichi Tanaka
i've used the PIC LEARNING from his web page
to build my IR system. A transmitter several receivers and speed control with drawings and hex codes he provided.
He could have just as easily profited from his
ideas but made them public instead.
Thanks again
Aug 30, 2003, 12:45 AM
Registered User
Gearbox for 4mm x 8mm motor, 24.5:1, 1.4 gram.
With balsa prop 1.7 gram.
Uses spruce for supports and 1mm steel prop shaft.
These could be replaced with balsa and CF rod reducing weight.
Gears are from old servos, they look about M0.2.
Aug 30, 2003, 12:53 AM
Registered User
Sep 01, 2003, 07:07 AM
Thats NOT indestructible
j8m8l's Avatar
Hi Dave.

I am planning on doing a similar thing for a school "project".
Are you going to power the motor off the charge pump DC-DC or add another converter?

Josh Levine
Sep 01, 2003, 12:05 PM
Registered User
Motor runs off LP cell, 3.6V.
Not off charge pump, thats for the 5V pic.
No converter.

Model come in just under 9 gram, could still easily knock some weight off.

Had a few short straight and level hops tonight.

Sep 03, 2003, 05:04 PM
Registered User
billystiltner's Avatar
This is a nice gearbox. Well everything is nice actually.
I am curious how you fit the gear on the motor shaft.
It looks like the hole in the gear is too large for the shaft.
I have a similar problem with clock gears and a 6mm car motor. Trying to get a 2 stage gearbox going with 8:1 ratio for a bit plane. I am also curious about the prop you end up using what diameter, chord, and pitch. Did you glue the spruce together for the gearbox or is it all one peice?

Nice work!
Any other details on the gearbox will be greatly appreciated.
Sep 03, 2003, 08:00 PM
Registered User

The hole in pinion was to large, I sleeved it with plastic tube, it may even have been wire insulation.
Lighters, including wind proof type are a source of small brass tube and fittings.

For 6mm bit motors 9:1 - 16:1 ratio and 127mm x 64mm - 160mm x 120mm prop would be close depending on motor and ratio. Ratios up to around 12:1 can be made with bit gears.

Spruce pieces glued together.

Last edited by david_dewit; Sep 03, 2003 at 10:15 PM.

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