Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Gyro Design Question - Puller Engine Positioned At Rear Of Craft

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Gyro Design Question - Puller Engine Positioned At Rear Of Craft

Old 17th Aug 2017, 17:16
  #1 (permalink)  
Thread Starter
 
Join Date: Aug 2017
Location: Harrisonville, MO
Posts: 4
Gyro Design Question - Puller Engine Positioned At Rear Of Craft

I'm a tinker type and been wanting to build a gyro for some time now. Been doing a lot of research and it seems the greatest safety factor (aside from the pilot) is longitudinal stability. Secondarily seems to be rotor impact on the air frame or prop.

Generally I tend to think if nobody's doing it then it's likely not a good idea - pioneers tend to get their wagons burned. But I have to ask the experts. Why doesn't anyone mount the engine in the rear but with the prop in front more towards the horizontal cg?

It seems having the weight (pilot and engine) coupled near the horizontal cg would tend to negate the potential for the weight to counteract PIO. I'm not an engineer but it seems moving the pilot and engine weight outward toward the respective front and rear would increase longitudinal stability as long as the horizontal cg is properly managed. It also seems having the prop positioned mid-craft would lessen it's potential to induce PPO and essentially eliminate prop strikes.

Am I crazy, ignorant or suffering from some other defect?
williambbusby is offline  
Old 18th Aug 2017, 04:00
  #2 (permalink)  
 
Join Date: Jun 2013
Location: Thaïland
Age: 62
Posts: 183
This shape exist already for years, but no commercialised. The main problem to solve is the shaft between engine and propeller : Weight, place to be installed in a single seat ? balance ( when runing) 2 cardans , etc.... i don't have the reference now, maybe i find it and forward to you..
BOBAKAT is offline  
Old 18th Aug 2017, 10:10
  #3 (permalink)  
 
Join Date: May 2017
Location: Wrexham
Posts: 54
P-39 and P-63 had mid mounted (rear of pilot) puller motors with prop up front if that helps. You may get some ideas from their designs.
Animal Mother is offline  
Old 21st Aug 2017, 12:56
  #4 (permalink)  
Thread Starter
 
Join Date: Aug 2017
Location: Harrisonville, MO
Posts: 4
Bobkat, ths for the reply. I envisioned the propeller would use the same conversion as a rear mounted prop (I've got a Subaru EJ22 available). I plan on a two place craft but haven't decided on side-by-side or for/aft configuration. What do you mean by balance when running? What cardans are you referring to? Any references you can find would be most appreciated.
williambbusby is offline  
Old 21st Aug 2017, 12:57
  #5 (permalink)  
Thread Starter
 
Join Date: Aug 2017
Location: Harrisonville, MO
Posts: 4
I assume you don't mean the WW II fighter craft and googling 'p-39 gyro' or 'p-63 gyro' hit nothing aside from the fighters. Do you have any information on these craft?
williambbusby is offline  
Old 22nd Aug 2017, 03:32
  #6 (permalink)  
 
Join Date: Jun 2013
Location: Thaïland
Age: 62
Posts: 183
French design Propeller in front /engine on the back https://www.youtube.com/watch?v=OXHYkEg8BtY
BOBAKAT is offline  
Old 22nd Aug 2017, 12:06
  #7 (permalink)  
 
Join Date: Jan 2000
Location: Location, Location
Posts: 365
Why not have the engine in front and the prop out back? Can warm your toes nicely on the engine and no howling gale in the face.
Robbo Jock is offline  
Old 22nd Aug 2017, 12:27
  #8 (permalink)  
 
Join Date: Jun 2013
Location: Thaïland
Age: 62
Posts: 183
when you drive a wheelbarrow where is the best place for you ?
BOBAKAT is offline  
Old 22nd Aug 2017, 14:06
  #9 (permalink)  
 
Join Date: Jan 2000
Location: Location, Location
Posts: 365
On a comfy seat well away from any mucky stuff, with a beer, offering any advice and encouragement deemed necessary.
Robbo Jock is offline  
Old 23rd Aug 2017, 05:39
  #10 (permalink)  
Thread Starter
 
Join Date: Aug 2017
Location: Harrisonville, MO
Posts: 4
Well, what I'm asking is having the engine mounted directly on the engine just behind the pilot. By moving the pilot and engine away from the cg it seems the weight distribution would counteract any tendency for porpoising or PPO. But, as I said I'm entirely ignorant in these matters and trying to learn.
williambbusby is offline  
Old 23rd Aug 2017, 11:58
  #11 (permalink)  
 
Join Date: Oct 2009
Location: Old Hampshire
Age: 63
Posts: 556
Ken Wallis did some thinking about where to position engines on autogyros especially when considering two small engines rather than one large one. I have a copy of the report he wrote and it shows configurations such as a tractor engine in the nose and one behind the pilot. A tractor and pusher in line astern behind the pilot. Side by side pushers behind the pilot with separate propeller arcs. Side by side pushers behind the pilot with overlapping propeller arcs. Side by side engines driving a common shaft. Side by side engines driving contra rotating props on the same axis.
Of all these concepts he actually built and flew the tractor and pusher in line astern (propeller to propeller) behind the pilot configuration (G-BNDG)
VX275 is offline  
Old 23rd Aug 2017, 13:52
  #12 (permalink)  
 
Join Date: Feb 2005
Location: California
Posts: 344
Why don't you build a couple of radio-controlled models, electric power, and try out your theories there?
A lot safer, less expensive, and it'll save on laundry bills when things don't quite work out.
Joking apart, follow the KISS priciple.
Regards,
f
fleigle is offline  
Old 24th Aug 2017, 03:07
  #13 (permalink)  
 
Join Date: Mar 2005
Location: Poplar Grove, IL, USA
Age: 53
Posts: 836
How about a tractor with the engine up front?
Little Wing Autogyros, Inc..
IFMU is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.