Can anyone clue me in to a guide on rotor sizes and minimum/maximum RPMs needed?
35cc gas engine (3000 - 7000 RPM) --- 4-way speed increasing gearbox --- 4 x right angle speed increasing gearboxes (2 x CW& 2 x CCW) --- variable pitch props.
Weight 25 - 30 lbs
Props ~ 24 inches
I'm waiting for the tech supports at the gearbox companies to give guidance on high RPM bevel gearboxes.
What type of blades would fare best for this application?
What RPM levels would I need to maintain hover and flight with 24 inch props and 25 lbs?
Naysayers - Redundant failsafes, backups and safety features will be paramount in this design in the long run.
You may not be getting a bunch of responses since most of us are using fixed pitch/direct drive electric power trains in our multi-copters. Which BTW, can scale to carry the kind of weight you spec'd.
I wish I could help you out more. There are similar issues to work through with fixed pitch/direct drive setups such as prop size and RPM's, but you are adding a few more variables with variable pitch, constant speed rotors.
Keep safe in AFG.
I realize that the majority are using the BLDCs but I would like to design reliability into this monster.
If a BLDC motor dies can the other three carry the acft back to the helipad? Maybe the code can convert to a Y airframe config. I would buy four of the monster Hacker A50s if I thought I could get enough power on board to keep it afloat for more than a few minutes. I even looked into putting a IC engine onboard to run alternators that would help with power but everyone treats me like I'm trying to turn a turd into a snickers bar. I have asked unanswered questions that I am apparently too dumb to figure out for myself. I wish it were that easy so I could plug in a target weight and get answers on Motors, props, ESCs and batteries. I appreciate any tidbits of knowledge at this point.
Many things are based on trial and error in this hobby. I usually try to calculate as much as possible but then I make a sample for proof of concept. If that works I build the project. Usually I make the adjustments needed and then reconstruct the project based on the experience made,
I try to give some more answers to you catalog.
1. total airframe weight. I think that 25 - 30lbs should be the target. Thats up to you.
Everyone please help adding to the list and putting ideas on the comments.
Thanks again Christof,
I wouldn't have any control, on the four rotors at constant speeds with fixed pitch blades with belts or gearboxes. I haven't seen any development or discussion on any posts about the ArduCopter code dealing with quad variable pitch systems. Way beyond my scope to write code... maybe one day.
No I do not think so. You would use as governor on the engine side to keep your rpm constant. The PID System of the ACM code should allow you to adjust your system with collective pitch over swashplate (I guess). Just your servos have to be fast enough. You can supress the vibrations to a certain degree. I would give it a try.
The other solution is using 4 big eMotors in gov mode and still go with collective pitch.
Here is a more structured question. I have been looking at some of the Hacker motor combos and am thinking about going that route to get started and practiced with all of the stuff on DIYDrones.
I won't give up my gas powered dream, but have to get my hands on now. I'm good at soldering, even surface mount by hand, and good with wires and cabling, mechanically inclined.
If I were to use one of the TRex 500 combo sets x 4:
Would one of the three blade props 14 - 16 inches x 10 pitch found here work OK on a quad?
I am asssuming, probably wrong, that with a stronger motor and a higher pitch, I could calibrate/program the ESCs at a lower RPM rate to use the power to my advantage with more weight on board.
If this is totally wrong, which prop would be better for a 500 sized motor and do three bladed props give more power? No sweat if not, I'm just hoping for more lift power at lower power consumption. The three blades are heavier than two....so maybe not.
You can do some calcs here.
attached is the answer to your question.
I came up with two possibilities for the 5 lb per motor.
A whoppinhg 6 - 8 minutes of flight time! LOL
Should I be calculating for 7.5 lbs per motor to factor in the extra 50% for maneuver?
Thanks for all the advice/mentoring.
Recalc with propeller airplane when you intend to use airscrews. Best is to use an APC airscrew, they are very efficient. Yes, add the extra 40-50%.
Lets say you want to lift 5Kg, system weight is 10Kg then look for 6-7Kg thrust per motor.
Please check this post and tell me what you ideas and comments are appreciated if you would...
William, I am sorry, I went to far. If I saw you face to face I would not talk like that.
I deleted that comment.
The technical part I stand by. Helo rotors are geared down from the engine a lot. If I were you I would look into single rotor heli crafts and use their numbers as a guide *4.
I am here to learn. I know that many of you have spent years in this craft and science. I was a tech for a while in the mil but I only built electronic surveillance devices and antennas, etc..
I really am excited to get started and I am studying daily. I will reach out to all that I can in search of answers and help. If the rotors don't have to be at 10,000 RPM maybe I can go straight 1:1 on the gearboxes. The speed increasers have been the stumbling block. I still am stuck on the notion that a gas engine can last and turn radial rotors.
I found variable pitch props...only 9,000 per! That was just an idea that I thought would bring flexibility to a heavy hard to manage stability craft.
Take a deep breathe and give a brother a chance!