stunthanger.com
General control line discussion => Open Forum => Topic started by: Bob Reeves on December 19, 2006, 07:15:56 AM
-
Thought someone might be interested in how I made a stock Brodak spinner fit my Saito 56..
Main machine work was done on the adaptor nut. I first drilled the 1/4 28 threads out of the Engine end using a 15/64 drill bit to a depth of 1/2 inch. This is the proper tap drill for the M 7x1 metric engine shaft. After taping the new hole I cut .015 off the end to give the extended part I was going to taper close to the same dimension as the Saito lock nut.
By eyeball and a protractor I guessed at the lock nut taper and came up 22 deg. May not be perfect but it works. I then machined the taper on the adaptor nut. This allows the adaptor nut to act as a replacement for the stock lock nut.
After measuring everything I determined I needed to cut .2 inches off the front of the adaptor nut and cut the stud on the front bolt down to .270. The picture below shows the stock parts beside the modified parts.
One caution is the Brodak adapter nut is aluminum so I wouldn't get too carried away tightening it on the prop shaft. All it has to do is help the prop nut stay tight and hold the spinner on. Over tightening it could strip the threads.
-
Nice machine work, Bob
From Keith an amateur metal butcher
-
Bob - not to nit-pick but did they change the crankshaft thread diameter? :-\
My SAITO .56 (very old) has a 7 mm x 1 mm thread, not 6 mm. ??? ???
Bob Z.
-
Nope, typo or brain f**t on my part. Think I did get the drill size right but am not in the shop to check. Thanks for catching that...
-
Hi, Bob - the reason I asked is that I make custom prop nuts to any specifcation. Very often, I will get a request to "adapt a 1/4-28 spinner nut to my ENYA" or some such.
I just measure one of my own engines and cut the threads.
One thing I thought of - the original SAITO .50 and .56 used the same crank - a 7 mm thread.
Maybe the later ones were changed???? ??? ??? ???
Bob Z.
-
No change: checked the Saito web site and 56's are still 7x1, not sure what I was thinking when I typed the 6, was a couple days after I actually did the work and somehow had 6 mm on the brain...
-
The one that bugged me was the OS .15 thread...four of them...I can't recall what it is, but something bizarre like eleventeen thirtysixths. I just modified stock OS items, because the tap would have been about $40, from memory. PW was paying the bills, anyway...
I put some hours into adapting a Dave Brown spinner to my DS .60bb. The neat thing about it is that the prop sits on the prop driver knurling, just like it should. The spinner backplate has a counterbored hole that sits on on the step on the prop driver, just like the DS spinner. Darned fine idea, OBTW. y1 Steve
-
Hi Steve,
Your comment on the DS got me to thinking....... I have a Sirotkin Ilushyn in the not too distant future plans. I will be using an Akrobat .42 which is like Sirotkin used......... thing is, the plane has a very "Mig 25" (??) type nose, there is an adapter of some sort to allow the spinner to sit "inside" the nose cone of the fuselage. Gotta look over the plans and see what has to be done! y1
Classic legal Russian model and *I believe* Sirotkin's last competion plane. An elliptical wing I-beamer (sorta) and a pretty good departure from his earlier Spacehound. Plus it has "bicycle" fuse mounted gear (U-2 style) and wing tip wire "skids".