David Eichstedt

My Feedback: (17)

I need some detailed data on fuel consumption for engines in the 100-150cc range. I work for a major aerospace supplier and we need this data for a real UAV project.

I'm looking for more than just "I can fly for 20 minutes on 32 oz. of fuel." We need fuel consumption at various power levels or throttle settings, and I'm looking to see if someone can help us gather that data.

Yes, I've already done a search of this forum on fuel consumption and come up empty (no pun intended).

Thanks,

David

Scar

My Feedback: (3)

Ha! Like we keep that kind of data!

You'll probably have to do the thermo calculations, or set up a test cell with fuelmeter and such.

Your observation about the guy who could fly so many minutes on so many ounces of fuel is probably about right, and about the best you'll get from us. Even if we did have that kind of data, well, we'd probably lie a little...

Where I work, the instrumentation would be part of the engine test cell. Our smallest dyno is a few hundred hp, though.

Good luck,
Dave Olson

Kris^

My Feedback: (1)

I'll be flying my 150cc powered (with pipes) DR109 today, as well as my BME102 powered Fiberclassics Extra. . I'll dedicate some time to running the engines on the ground (lashed down) at different power settings and let you know what I get. Both motors are on tuned canisters. I'll set up a mix switch for 3000,4000,and 5000 rpm static rpm on the ground and you should be able to draw a correlation from there. Luckily, the planes are on different transmitters, so I can run one while I fly the other

Thing to remember, prop size does make a difference in RPM in the air, which will also make a difference in total fuel used.

A bit of quick info, though. when I 'ran-in" my BME about a month ago, Iused a 32-ounce tank. The motor ran for an hour at 1/3-1/2 throttle setting, swinging a 28-10 prop, and still had 5-6 ounces of gas left in the tank. As well, my RCS180 (30cc) will fly for an hour at very reduced throttle settings (2 clicks off idle) and use 18 ounces of gas. I did a 2-hour duration flight that used just 37ounces, including runup and takeoff.

A good source for this type of information would be Desert Aircraft or Aircraft International. They would probably have the ounces/minute fuel consumption at full throttle for you.

pe reivers

There is (was?) a guy named Ricardo who had a test set-up with fuel measurements in order to define pumping efficiency as well as fuel efficiency.
From my work as ship's engineer, I recall using a device to mesure the fuel consumption under partial load, so we could deduct efficiency from the registered indicated pressure diagrams.

The modelling community does not do these things. They indeed fly X-minites on an Y-volume tank, and manage Z- minutes with clever throttle management.
The participants in this hobby range from non-skilled to highly educated, whith spear head on having fun. That means that most calculations are based on thumb rules. (by no means dumb rules)

David Eichstedt

My Feedback: (17)

Kris^,

Thanks for doing this check for me. It won't be completely scientific, but it will be a huge step in the right direction. When you report back with the data, be sure to get me as much pertinent data as possible, such as prop size, temperature, humidity, altitude, etc. You probably don't have some of that info, but you may be able to get a local reading from weather.com that will get you in the ballpark. With the right information and some assumptions regarding the power curve for the engine, we can probably get enough information to make some reasonable choices.

The right way to do this is of course with a dynamometer, but that would require a volunteer who would let us measure their engine.

I'm actually not on this project at the moment, but another engineer who is asked me for some help since I'm a modeler. This other guy already contacted Desert Aircraft and they didn't have any of the detailed information we're after.

Again, thanks for the help.

David

Kris^

My Feedback: (1)

Flanker, I have to apologize. I went out and bought a 1.5 ounce tubular measure to fill and then time as it emptied, but to no avail. . some of my IMAC and Pattern buddies were already at the field and it turned into a flying festival. 15 flights from two planes in 6 hours. I DO know that in all this flying I never ran out of gas. . .and most times I landed with half a tank during 12-16 minute flights. . 32 ounce tank on the 100 and 50 ounces on the 150. Given the expected weather on Sunday, the first day with a LONG evening, I'll try to get some measurements for you after I get home from work that evening.

Again, I apologize, but I'll try to get the information when I'm able to.

rc bugman

My Feedback: (30)

Flanker,

In my research, I am always faced with the lack of information about fuel consumption for these engines. The rule of thumb which I have found to hold for 3W engines is the fuel consumption per min at full throttle equals the displacement in cc. This is a moderate overestimate of fuel consumption and builds in a small reserve when sizing the fuel tank.

You will have to purchase the engines of interest and measure the fuel consumption vs power for yourself.

Elson


Elson

james04

Please be carefull

Flanker says he is working on a "real UAV project" and none of us knows who Flanker is. My point is after September 11 giving advise on how he can build a drone can be detrimental to out hobby. If a paranoid politician got a hold of such a conversation it could be used to pass laws that would outlaw the use of R/C aircraft. Some of the members in my R/C club have already been approached by detectives asking if it was possible for one of our models to carry explosives. This is not a joke so please be careful about what kind of advise we are giving.

Thanks

David Eichstedt

My Feedback: (17)

Thanks a lot, james. That's really helpful! If I had purported to be a student working on a UAV project (as someone else did on this forum), would your advice have been any different?

If, as a result of james04's post, anybody has decided not to help me, just send me a PM and I'll provide some RCU references regarding who I work for and what I do.

If we let such fears stop us from discussing anything of a technical nature on these forums, then we're being controlled by fear and thereby grant a small victory to the terrorists. Without technical discussion, much of RCU would become meaningless. In that case, we might as well go back to getting all our information from the modeling press.

Fuel consumption of a model airplane engine, while important information for performance calculations, is hardly export-controlled information. If you want to keep the terrorists from using model airplanes as weapons then do everything you can to safeguard autopilot and avionics technology from public disclosure.

Be careful, not paranoid.

David

james04

Maybe I am just being paranoid. But with detectives coming down to the flying field asking such questions, something is in the works. I more or less just would like to make the people aware of the potential for change after September 11th. I'm still fairly new to this hobby and would hate it if it were baned.

I agree we should be careful, not paranoid.

James

Barry_G

My Feedback: (26)

I'd think an Aeronautical Engineer would be able to figure that out. :-)
I couldn't let that one pass, Dave!
Barry