Azimech

[Stock Helicopters & Turboprops] First flight around Kerbin! (page 49)

1756 posts in this topic

Posted (edited)

47 minutes ago, EpicSpaceTroll139 said:

Out of curiosity, have you tried one-piece turbines* using parts such as fairing bases? Like the Mk2 cores, they don't expand as their COM is in line with the shaft. Is the reason for the multiple turbine elements because they withstand heat better? I imagine heat tolerance might be a bigger issue for your helis as their lower turbine radius (1.25meterish) requires more thrust impinging on the turbine than my over-sized (1.88meterish) turbines for the same torque... I think... Correct me if I'm wrong.

*I've actually tried multi-part turbines, though the reason I've used them was for space saving reasons. For example on coaxial designs I can have a bearing for one rotor inside the turbine for the other

I look at a couple of things. Because with my big designs the turbine shaft is allowed to flex in its housing, collisions may occur with other parts during high speed or aerobatics. Fairing bases and heat shields can't take a lot.
Heat tolerance is secondary for me.

41 minutes ago, qzgy said:

I believe he has, using a heat shield for his new smaller turbine design.

@Azimech, correct me if I'm wrong\

 

Also, mind showing a picture of your coaxial design to me? I've been trying to make a coaxial thing for a while, haven't been able to get something small enough that's powerful enough...

Sure, no problem.

 

Wait for it ...

 

 

Little joke there. That "thing" is the first coaxial turboshaft in existence, made almost 2.5 years ago. I'm glad I've never released that one, it's fugly.

 

There are either two solutions. The one is complex, have one shaft rotate in another, the other is just offset hacking. I prefer the first but I know the limitations (size, mass, drag, part count).

Here you can find both:

https://kerbalx.com/Azimech/77I-Azi29-Janus-v10
https://kerbalx.com/Azimech/77-Industries---CTR3-10

Keep in mind the CTR3 doesn't run, it was built in 1.0.4.

Here's a video with a later variant:

Now I know you'd like a compact, offset hack style coaxial. I haven't really built one yet but when I do, I'll make it public.

It will probably be with a 2.5m heat shield instead of 1.25, the smaller ones are just way too inefficient.

Edited by Azimech

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Posted (edited)

@qzgy Ah yes! I almost forgot! I noticed that a day or two ago when I tested out @Azimech's Apache prototype. On a funny note, I hope that those seats had some nice cushions. That thing was rattling around more than an unbalanced washing machine! :P Looked cool though! :cool:

Also, figured I might as well show qzgy the mechanism on one of my own Coaxial helis.

vmDSn3p.jpg

I pulled the rotor blades and the housing off so that things are easier to see. I also labeled the components.

1. Lower rotor one-piece turbine; spins clockwise

2. Upper rotor multiple-part turbine element, joined at the upper turbine hub (2.5); spins counterclockwise

3. Blowers for lower turbine and (3.5) upper turbine

4. Lower rotor/turbine retention pin

5. Upper rotor/turbine retention pin

6. Lower rotor top bearing (another one is hidden inside the fuselage of the heli underneath) *

7. Upper rotor top bearing, uses an experimental quad octostrut bearing (once again another bearing is hidden below)  *

 

*I don't remember the exact reason why the top bearing for the lower one is above the top bearing for the upper one, but it must have been to keep something from exploding. :P

 

Edited by EpicSpaceTroll139
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45 minutes ago, Azimech said:

Now I know you'd like a compact, offset hack style coaxial. I haven't really built one yet but when I do, I'll make it public.

It will probably be with a 2.5m heat shield instead of 1.25, the smaller ones are just way too inefficient.

Yeah, I've experimented with offset hacking for a "coaxial" rotor system.. Sorta worked, reliability was an issue and also making it fit into the model I wanted (that was actually the bigger problem.)

 

@EpicSpaceTroll139 Thanks! That's actually a really cool idea, using to turbine rotors stacked on top of each other like that. Why one multipart and the other one solid? I would guess it was for the lower retention pin, but I'm not sure.

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1 minute ago, qzgy said:

<snip> Why one multipart and the other one solid? I would guess it was for the lower retention pin, but I'm not sure.

Indeed that was exactly the reason for the multipart turbine, although if I ever do a rebuild, I think I could move the retention pin to some other location and thus save on part count. Might even reduce drag too, not sure.

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Oh wise and great turboshaft masters, I've been having a problem with a design of mine and I'm a bit stumped. I hope this is the right place to post this!

You see, I've found myself in love with the coaxial copter, the Sikorsky S-97 Raider. So I've set out to make my own coaxial design. I've come to a crossroads however. I'm debating abandoning the design and trying something new but I'd like to see if anyone has input before I totally go back to the drawing board. The two rotors are on separate action groups for testing. The upper rotor can achieve full throttle no problem, while the lower is just not having any of it, only achieving 1/3 throttle stably. I've adjusted and tweaked just about everything but the weak link seems to be the structural fuselage every time.

 

IDK ¯\_(ツ)_/¯  let me know what you think....

CMADWJc.gif

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3 hours ago, Krog34 said:

Oh wise and great turboshaft masters, I've been having a problem with a design of mine and I'm a bit stumped. I hope this is the right place to post this!

You see, I've found myself in love with the coaxial copter, the Sikorsky S-97 Raider. So I've set out to make my own coaxial design. I've come to a crossroads however. I'm debating abandoning the design and trying something new but I'd like to see if anyone has input before I totally go back to the drawing board. The two rotors are on separate action groups for testing. The upper rotor can achieve full throttle no problem, while the lower is just not having any of it, only achieving 1/3 throttle stably. I've adjusted and tweaked just about everything but the weak link seems to be the structural fuselage every time.

 

IDK ¯\_(ツ)_/¯  let me know what you think....

CMADWJc.gif

I'm guessing the hollow fuselage you're using is being pushed beyond the 10 m/s impact rating. I understand completely why you'd want to use it, it's a very elegant solution.

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