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General control line discussion => Open Forum => Topic started by: Bob Reeves on March 22, 2009, 07:22:28 PM

Title: Final touches on Pull Test Machine
Post by: Bob Reeves on March 22, 2009, 07:22:28 PM

Elwyn shot a few pictures of our finished PT machine today. The scale was printed on clear laser paper then laminated with SLC covering to protect the printing. A coat of clear Rustoleum will seal the edges and offer another layer of protection. Lee Thiel came up with the leather handle holders. Should be easy on balsa covered handles.

Title: Re: Final touches on Pull Test Machine
Post by: Howard Rush on March 22, 2009, 10:56:41 PM

Very nice.

Title: Re: Final touches on Pull Test Machine
Post by: john e. holliday on March 23, 2009, 08:36:50 AM

Looks great Bob, the old pull tests were done here in Tuscon at VSC.  The old P-39 with LA 46 is hardest I have yet to pull. 

Now would you manufacture them for clubs with special order and gaurantee the accuracy.  I know a couple of people that are fanatics about pull tests. 

Then again maybe some manufacturer would make them with weight scales, like for carrier, speed and combat. 

Having fun,  DOC Holliday

Title: Re: Final touches on Pull Test Machine
Post by: Bob Reeves on March 23, 2009, 12:57:41 PM

Hi Doc, won't be seeing me go into production but am going to do a little write up with details in case someone wants to duplicate the design.  With a little ingenuity It could be made with less machine work using off the shelf parts. I enjoy developing this kind of stuff but after the first one it becomes work.

Title: Re: Final touches on Pull Test Machine
Post by: Larry Fulwider on March 23, 2009, 08:41:04 PM

Bob --

Did you ever find the reason for the non-linear (semi-sine wave or whatever it was) jump in the scale? Last I heard it was still a mystery. From the pic above it looks linear.

Things that don't add-up-out bug me forever, so if you don't have the answer, make one up, OK?

Larry Fulwider

Title: Re: Final touches on Pull Test Machine
Post by: Bob Reeves on March 31, 2009, 02:42:59 AM

Quote from: Larry Fulwider on March 23, 2009, 08:41:04 PM

Bob --

Did you ever find the reason for the non-linear (semi-sine wave or whatever it was) jump in the scale? Last I heard it was still a mystery. From the pic above it looks linear.

Things that don't add-up-out bug me forever, so if you don't have the answer, make one up, OK?

Larry Fulwider

Intended to answer this earlier but completely slipped my mind...

Larry, after conferring with our local colledge professor we concluded that no matter what the fish scale I was using was reading the actual pull will be linear. Rather than go against the laws of physics I made a new linear scale and compaired it with the actual reading I was getting on the fish scale. The differences were actually small and almost always in favor of the low side. I concluded a linear scale would look better, make more sense, be difficult to argue against and actually be more accurate than a fish scale.