Thread Tools
Oct 15, 2001, 03:19 PM
AMA 697691 / FAA 13675
Thread OP

Weight Reduction Techniques for Micro-Flight


Without getting into the actual catagory this belongs in, slowflyer, indoor, or micro-flight, (or even Modeling Science ) I am looking for suggestions or techniques to reduce the weight of R/C gear in models that weigh <5oz.

Many of the indoor models seem to hit a lower limit based on adding R/C gear and the flight pack. The best value for weight vs. cost seems to be in products like the Hitec HS-50 servo, GWS R4-P micro-receiver, and GWS ESCs, motors, etc.

Lighter weight, more expensive components are available from specialty places like Hooks & Rigging in Canada.

Has anyone used only 1 servo for rudder/elevator control? A fixed elevator can be used but is tricky to fly indoors.

How about R/C solenoids that merely provide 2 positions. Are these available? Do they weigh less than an HS-50?

I've heard that some 70mAh NiMH cells are available. What are some sources to buy them?

I see that Keith Shaw has several dual AF Firefly model planes. Does anyone have a model for a single AF Firefly, Puma 050, or S-100 Hummingbird?

Food for thought...thanks for any information provided.
Latest blog entry: Greg's Web Hangar
Sign up now
to remove ads between posts
Oct 15, 2001, 04:15 PM
Registered User
Cloud 9 RC has some nice lightweight alternatives at reasonable prices. The BIRD (built into rudder device) magnetic actuators are about the same price as HS-50s, but much lighter (1 gram each).


http://www.rcmicroflight.com/cloud9rc/index.htm
Oct 15, 2001, 05:47 PM
DNA
DNA
registered user
DNA's Avatar
Interesting topic...

http://www.rcmicroflight.com/jul01/lgst_funfly9.asp
Oct 15, 2001, 08:37 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
If you subscribe to RC Microflight, see one of John Worth's columns in the past several months where he had a picture of a plane he built with a coupled rudder and elevator. Others use the throttle, more of it and the plane goes up, less and it goes down. This also saves weight.

I have some of the 70mAh NiMH cells. You can get them from Dave Lewis http://www.homefly.com. I have a web site where I'm posting results from static tests http://people.ne.mediaone.net/gordonjohnson/ . These tests are not perfect and I'm learning as I go along. I have tests of the Kenway KR-1 on 70mAh packs of 4, 5, and 6 cells. So far, the results have been less than stunning. I've also corresponded with someone in the St Lewis area who said the best he could get out of the 70's was two laps around a basketball court. Todd Long told me that the most he could pull out of the 70's was 1/3 amp, and that was why he was not carrying them. The results from the 120mAh cells (available from Cloud 9 RC http://www.rcmicroflight.com/cloud9rc/index.htm as well as Dave Lewis) are much more encouraging. I'll be flying my 50-60gram (the weight depends on which motor/gear and battery pack is used) Flying Aces Stick indoor for the first time in about two weeks. I'll post what I learn here and on my web site.

In terms of weight and components, I'll post all my info on my site soon. I'm using 3g Westech servos, a Sky Hooks 3g receiver, and a JMP Esc (with the voltage cutoff disabled). Batteries are the key, and so far the 70's are looking iffy.

If you are interested in this area, a subscription to RC Microflight might help. At $30 some think it is expensive. But, you get online access to all the old issues (about 3 years), so you can get up to speed on a lot of stuff. I enjoy my subscription. It's about half the cost of just one Westech servo.

The Flying Aces Stick (RC Microflight plan) was mentioned and had pictures in a column in Electric Flight International nearly a year ago. The person written up in the column was flying the plane with 3x50mAh NiCd cells and a Pixie 7P ESC and two Westech servos on a Firefly. I have never been able to figure out if he was using the bare Firefly without a gearbox, or the 4:1 or 16:1. So, I compromised and went with the 4:1. The guy in the article got his third version of the plane down to 50g. I've taken this as proof that it can be done and that a Firefly will power it. I've got some tests of the Firefly with the 70mAh cells. It seems pretty weak. Using the rule of thumb of AUW of three times thrust (some people say four times) it's difficult to imagine the 70's powering this plane at ~50g if fitted with a Firefly.
Last edited by Gordon Johnson; Oct 15, 2001 at 08:55 PM.
Oct 16, 2001, 09:16 AM
AMA 697691 / FAA 13675
Thread OP
Wow! Great responses guys, thanks.

When it comes to R/C, I feel like a sponge soaking up water.

I will subscribe to RC Microflight since it appears to have some unique information on this subject.

The BIRD devices that Dave mentioned may be exactly what I was looking for. I can't argue with 1 gram each!

The smallest cells I own are the 120mAh NiMH cells. I was skeptical about the 70mAh cells and it sounds like it was warranted.

I have the 4:1 Firefly and it runs great on a 4" to 5" prop using the 120mAh cells. I use an 8-cell pack and a 4.5x4 prop draws about 480mA.

DNA,

Thanks for the link! Very interesting stuff. I see that page 1 has a writeup on our recent visitor to the E-Zone; GWS CEO, Houng Lin.

Regards.

PS Nice graphs, Gordon
Last edited by Greg Covey; Oct 16, 2001 at 10:43 AM.
Oct 16, 2001, 01:50 PM
AMA 697691 / FAA 13675
Thread OP
I got my subscription to RC MicroFlight.

Of course, now I've spent the entire work day "soaking up" past issues.
Latest blog entry: Greg's Web Hangar
Oct 17, 2001, 07:57 AM
AMA 697691 / FAA 13675
Thread OP
Gordon,

After viewing your graph of the Firefly on 5-cells using a GWS 6x5 prop, I went looking in my rather large prop supply but only found a GWS 7x3.5 prop.

I fired up the Firefly with this prop and set my power supply to 5 volts. I was using the AF ESC for the Firefly and a GWS R4-P receiver. The AF ESC has current limit protection for the Firefly built-in.

The thrust seemed fantastic and the current draw was right around .5 amps! I can measure RPMs but I'm not sure how you are measuring thrust.

Can you try this setup if you have a 7x3.5 prop?

My initial test on the COX Viper almost flew it using 8-cells on the stock Viper 4.5x4 prop. I now feel that I should go back and try it again using only 5 cells and the 7x3.5 prop.

What are your thoughts about this setup?
Latest blog entry: Greg's Web Hangar
Nov 08, 2001, 04:53 PM
Registered User
You might want to try the 100mah NiMh cells from Cloud 9, I get about 15 min. on my PF 5. 4oz 23" span airplane. I charge them a .3mah. I have about 30 flights on them so far.
I'm buying a Orbit charger that will plot the batteries on my computer to track the performance better.

Kirk Krest
Nov 08, 2001, 05:46 PM
Registered User
nolasco's Avatar
15 minutes using 100mah cells on a 4oz plane?!!! Are you sure?

That translates to around 1/4 amps for current. What prop, motor, and gearing combo are you using? I could use one of those.

Jun Nolasco



Quote:
Originally posted by Kirk Krest
You might want to try the 100mah NiMh cells from Cloud 9, I get about 15 min. on my PF 5. 4oz 23" span airplane. I charge them a .3mah. I have about 30 flights on them so far.
I'm buying a Orbit charger that will plot the batteries on my computer to track the performance better.

Kirk Krest
Nov 08, 2001, 06:08 PM
DNA
DNA
registered user
DNA's Avatar
I couldn't believe it either when I first tried out my DC 5-2.4.

With an 8:1 gear and a 6x3 prop, I connected it to a 9V Ray-O
and sat their holding it, thinking it would only run a few minutes.
Well, 30 minutes later I was Still sitting there holding it and it
was still running at full speed. I thought something was wrong.
So I used another 9V Ray-O and this time I measured the
current draw. It was only 300ma. A 6x3 prop is pretty small
for this combo, it usually uses one much larger, but further
testing is in the works.


Quick Reply
Message:

Thread Tools