Prather Pitch Gauge
11-19-2013, 04:27 AM
#5
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Ahhh... I get you now... Well, that I understand, but I'm trying to maxamize my $'s..... Could really use some extra cash for Xmas and maybe a trip... Just selling off a few odds and ends that appear to be highly coveted at the moment..
11-19-2013, 07:18 AM
#8
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Dave people are willing to pay real money for old stuff ???? I have one here somewhere in my "Hobby " stuff I'll have to look for it
I didn't know you could get $$$$ for old stuff haven't used it since we quit Quarter midget WOW
I didn't know you could get $$$$ for old stuff haven't used it since we quit Quarter midget WOW
11-19-2013, 07:21 AM
#9
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Some are I guess Al... One of these sold on EBAY for over $100 recently... I guess some of the Control Line guys still use them, and some still use them for Q40 props... I just take em out of the bag and go...
Trey, I'll do my best to scan these in the next day or so. PM me your email.
D
Trey, I'll do my best to scan these in the next day or so. PM me your email.
D
11-23-2013, 08:23 AM
#18
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Shawn,
You can make a very good pitch gauge for not too much cash with a protractor. The Prather gauge was not all that accurate, as you could skew the measurements by a number of ways.
To build a prop gauge, I would start with a good digital protractor like this General Tool model for $30.
http://www.generaltools.com/1702--DI...OR_p_1245.html#
Next you need a measurement board. Use a flat sheet of aluminum, about 1/4" thick or maybe slightly thicker plastic that is a bit longer than the largest prop you want to measure and maybe 4 to 6 inches wide (It will need to be pretty wide to measure flatter angles at the tips of props).
Drill and tap on one end for the different stud sizes of the props you want to use. Might be three or more sizes, but if you run out of room on one end you can also use the other end too.
Finally mill or cut slots through the board for the protractor arm to go through the base at the spacing you want to measure. As I said before, the Prather unit's station spacing was in cm, so if you want a direct comparison to a Prather, go with that.
To use, mount the prop using a short thread or bolt to the base. Insert protractor from the other side and take a measurement. Do the math to find out the inches of pitch at that station.
If you find out that one blade is higher or lower than the other, don't change the blade, change the hub. If the front and the back of the prop hub is not exactly parallel, then it's a good chance that blades won't track in pitch. You can scrap the rear of the hub with a single edge razor blade to get them right with each other. Then go ahead to change each blade as desired.
You can make a very good pitch gauge for not too much cash with a protractor. The Prather gauge was not all that accurate, as you could skew the measurements by a number of ways.
To build a prop gauge, I would start with a good digital protractor like this General Tool model for $30.
http://www.generaltools.com/1702--DI...OR_p_1245.html#
Next you need a measurement board. Use a flat sheet of aluminum, about 1/4" thick or maybe slightly thicker plastic that is a bit longer than the largest prop you want to measure and maybe 4 to 6 inches wide (It will need to be pretty wide to measure flatter angles at the tips of props).
Drill and tap on one end for the different stud sizes of the props you want to use. Might be three or more sizes, but if you run out of room on one end you can also use the other end too.
Finally mill or cut slots through the board for the protractor arm to go through the base at the spacing you want to measure. As I said before, the Prather unit's station spacing was in cm, so if you want a direct comparison to a Prather, go with that.
To use, mount the prop using a short thread or bolt to the base. Insert protractor from the other side and take a measurement. Do the math to find out the inches of pitch at that station.
If you find out that one blade is higher or lower than the other, don't change the blade, change the hub. If the front and the back of the prop hub is not exactly parallel, then it's a good chance that blades won't track in pitch. You can scrap the rear of the hub with a single edge razor blade to get them right with each other. Then go ahead to change each blade as desired.
11-23-2013, 10:18 AM
#19
Thanks Bob, pretty much what I was thinking. The thing that I didn't think about was adjusting the hub. The goal is to see how small a dia I will have to go to get a YS 115 to spin a 15 or 16 inch pitch prop at 10k. Then decide if the airplane is clean enough to use the prop. I need to end up with an airplane that is close to 190 mph. Wings are getting sheeted this weekend.
