Propellers?

[TheDestroyer111]

I'm gonna stand out of this section by asking a question that isn't explained (or even told of) ingame: How. To. Build. A. Propeller?????? Seriously, I encounter some really unexpected things when building such devices and I have no idea of the theory behind IRL props. First of all, no matter how I build a hinge, the propeller in it is very jumpy. But this one isn't as bad, as I recently reverse-engineered a Hazardish hinge (I tried doing it myself, but failed, so I downloaded one craft using it, saved the hinge into subassembly, and used it in a test aircraft. It worked quite well, still jumpy, but better). A problem is also "How should I rotate my prop?". Due to simplicity, most my propeller craft are reaction wheel powered, and some use tip jets. I tried to use jet engine exhaust (so, an engine with an internal rotation source), but it somehow didn't create any rotation and I soon recognized that tip jets give bigger rotation speed for less fuel anyway. Then, is probably the biggest problem. How to build the prop itself? I don't exactly understand what effects does rotation and forward movement speeds have on the prop. I found out that placing the wings of the propeller further out gives WAY better effects. A vehicle with a reverse-engineered hazardish hinge and one small reaction wheel to rotate the prop, with the prop itself being made of wing connector type E could barely move even with gravity hacked no matter how many blades it had. When the same engine had a prop made of two wctE's it could go 10 m/s with hack gravity (somehow, the inner wctE's created reverse thrust when I enabled aero forces overlay while going at max speed, and the outer ones always thrusted forward). When I mounted a single wctE, but on an I-beam, I got to 19 m/s without gravity. I tried different numbers of blades, this appears to change initial acceleration but do nothing with max speed. I also used different blade pitch angles, and higher pitch gives higher top speed (my 19m/s record is with 60^ pitch this gives terrible initial acceleration, but it accelerates pretty good after 5 m/s).

[Geschosskopf]

17 hours ago, TheDestroyer111 said:

I'm gonna stand out of this section by asking a question that isn't explained (or even told of) ingame: How. To. Build. A. Propeller??????

I would ask that question to @Majorjim.

[TheDestroyer111]

9 hours ago, Geschosskopf said:

I would ask that question to @Majorjim.

There's no such person like that. When I click on your link to his profile, it says: "File not found.". 

[Majorjim!]

Just now, TheDestroyer111 said:

There's no such person like that.

BOO!

 lol, I have made plenty of hinges and bearings but my main building focus has been on larger, more complex mulit craft mission packs. There are guys who work solely on bearing type craft and they would be better positioned to help you as it has been a while since I made a propeller craft and the game has changed a bit since then.

 @Azimech and the people who post to his threads should be able to help you guys. Thanks for thinking of me though!

[Azimech]

Thanks @Majorjim, for the reference. 

Okay, I'd like to see with pictures what you've tried. Propeller theory isn't that difficult and there are a few simple rules:

• Higher RPM = always better. There's a limit in Physx/Unity/KSP, it varies but it's usually  around 50 rad/s (477 RPM).
• Large prop diameter is usually a good idea, but it puts a strain on the bearings at higher RPM when changing direction.
• More blades is usually a good idea, but due to higher mass does the same as a larger prop diameter with bearing load at higher RPM.
• Variable prop pitch is always good.

I don't talk about tip jets or reaction wheel drives, I invented the turboshaft/turboprop engine with a reason. But ... following guideline works for both electric engines and turboprops.

Here's what you do: First you design an engine and make sure it runs fine without load. Then you add a propeller, start with a 2 bladed prop and make it variable (probe core, battery & control surface as prop blades). Make sure you have a way of reading your engine speed. I always use V.O.I.D., it's the best. Do not use Kerbal Engineer, it gives faulty info.
Find the max allowed RPM for your engine, then start adjusting your prop pitch and keep a safety margin for normal operation.

Those are some of the basics. For more info, click the link in my signature.