Go Back  RCU Forums > RC Airplanes > Extreme Speed Prop Planes
Reload this Page >

Graupner Speed Props

Notices
Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Graupner Speed Props

Old 04-06-2014, 09:20 PM
  #1  
MJD
Thread Starter
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,630
Likes: 0
Received 0 Likes on 0 Posts
Default Graupner Speed Props

I know guys are spinning these up in the 30's on NovaRossi .15's, .21's etc. in the speedcup circuit overseas. I have few in the prop drawer, the 6x5.5 being a particular favorite for perky .15's.

But doing the math on the safety limits in the Graupner instructions - 3438/(dia in meters) = max rpm, for this prop at 152.4mm dia, I get 22,560rpm and m=0.53 at the tip which seems pretty conservative. Hardly a "speed prop" if the 6" caps out under 23k.The large hub 6" APC's are 31.6k.
Old 04-06-2014, 09:29 PM
  #2  
combatpigg
Senior Member
My Feedback: (3)
 
combatpigg's Avatar
 
Join Date: Nov 2003
Location: arlington, WA
Posts: 19,891
Likes: 0
Received 1 Like on 1 Post
Default

I don't think I've ever seen one of their speed props.
There tolerance for liability / risk is driving whatever their safety factor is.
It would take a pretty healthy .15 to blow the blades off a APC 6x5, I think.
Old 04-07-2014, 06:31 AM
  #3  
MJD
Thread Starter
My Feedback: (1)
 
MJD's Avatar
 
Join Date: May 2003
Location: Orangeville, ON, CANADA
Posts: 8,630
Likes: 0
Received 0 Likes on 0 Posts
Default

I know they spin the snot out of them on Novarossi's ad the like overseas and say they work great. These props don't show up on shelves everywhere, but they have a 6x5.5 and 6.5 x 6.5 that are great .15 - .25 zippy props.

Now knowing what else to do I'd stick with the APC rule 190k/dia in inches. That pegs the 6" at a hair over 30k max, I can believe that.

Old 04-09-2014, 07:24 AM
  #4  
airraptor
My Feedback: (66)
 
Join Date: Jan 2004
Location: fairfield, CA
Posts: 4,191
Likes: 0
Received 0 Likes on 0 Posts
Default

I wonder if that 30,000 is true number? I wonder if those props are going flat at higer rpm. MJD can you take a APC put it next to this one. then take some picture and post on here. take one over head shot and one with the hubs held together so we can see the pitch of both props at the saem time.

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

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