Pitch Gauges

Stuka Stunt Main Forum · 26 of 26 known posts recovered

Peter Hess · Mar 21, 2001 12:21 PM

Are there commercially available pitch gauges, other than the one by Prather, that are realistic for using in our endeavors?
The technical information about the Prather pitch gauge that is available on the Tower Hobby web site says that its range is from 3" to 5" of pitch. Is that right? If so, how does one check for 6" pitch, for example?
Any comments, thoughts or suggestions would be greatly appreciated.
Peter

kdheath · Mar 21, 2001 01:27 PM

#1 source

I have been batting around the same question. Does anyone have a favorite pitch gauge, and is there a web site or published piece on the how-to-do for repitching props? You know us RCers-slap on a prop and wind it til it screams.........So I've not tried repitching. Thanks!

LNeumann · Mar 21, 2001 03:01 PM

#3 source

There was a thread going on that other board a while back on pitching props that I posted to (and got a lot of flack on) but we can start a new one here. Whether you use wooden props or carbon fiber, it is good to check your pitch and "correct" as necessary. Wood, being what it is, can warp, even after manufacture. So, after taking manufacturing tolerinces into account, and then adding the possibility of the prop "doing its thing" after it is cut, you might be surprised what your prized prop actually reads. Besides, prop size, like shoe size, is not a sure thing. How many people go into the shoe store looking for the size 13EEE, and, on finding a pair, say, "I will take this one." We try them on first to check the fit. We need to do the same thing with our props.

Leonard Neumann

EddyR · Mar 22, 2001 10:25 PM

#13 source

This same question came up on RCO two weeks ago and I had the answer then and here it is again for those who didn't see it.The August 1976 Model Aviation had a Five page article on building a pitch gauge.The author John Kilsdonk has just returned to controline flying as someone told me they saw his name in a resent Pampa mag.Bob Kruger is getting copies from him and updating it to CAD and soon i will be free to all.
Ed Ruane in sunny Florida

LNeumann · Mar 22, 2001 11:57 PM

#14 source

Bob sent me the article, and, when you look at the face, it isn't right. The pitch angles don't change as they must from station to station. I haven't read the article yet, and the concept is feasable (similar to the wood one I got from Beardon with the plastic gauge) but the accuracy is only going to be as good as the gauge on the face. If it is not, then the whole thing goes out the window.

Leonard Neumann

LNeumann · Mar 23, 2001 02:14 PM

#16 source

Bob is back to doing some calculating and I am back to racking my brain (that is another term for putting it on a shelf, I think) trying to figure this thing out, and both gauges may be OK, just different approaches to the way they register. John's follows more as a linear measurement of the bar, which may be the major difference. Bob is doing some calculations, and, if that one comes out, one could extend it a couple of inches and Bingo!

Leonard Neumann

LNeumann · Mar 21, 2001 02:54 PM

#2 source

The Prather gauge goes from 3 inch pitch to about 15, and, although the gauge goes further, the base only allows it to read up to about 11.5 inch diameter. Reading a 13 inch diameter prop leaves only about the last 3/4 leaning over, which isn't bad, but on anything above we are starting to lose accuracy. Even so, the higher the pitch and the longer the diameter, the more difficult it is to read and to set.

The Prather is the only pitch gauge I am aware of that is in (sort of) current production. George Aldrich says it was copied from one that he had imported from Germany. So, somebody, at some time, must have had one over there.

American Aircraft Modeler also had one in their magazine many many years ago with instructions on how to make it and with a full scale pattern on its pages for doing so. I got a gauge that Beardon of Bear Enterprises had made many years ago, and probably off of this plan. It has a wooden base instead of the aluminum base of the Prather gauge and a clear plastic gauge with a paper gauge glued to the back side, but, otherwise, works that same as the Prather.

You will note that I said (sort of) current production for the Prather, since they have been "out of stock" for over a year now. So who made the gauges for them, how they got them, I don't know. And why they don't have them now, I don't know, either. Maybe an enterprising individual ought to see about making some and expanding the base to allow at least a 14 inch prop to be read. With the advent of the new piped engines and now the 4-strokes, longer props are once again coming into vogue.

Leonard Neumann

Brett Buck · Mar 21, 2001 03:04 PM

#4 source

>Are there commercially available pitch gauges,
>other than the one by
>Prather, that are realistic for
>using in our endeavors?
>The technical information about the Prather
>pitch gauge that is available
>on the Tower Hobby web
>site says that its range
>is from 3" to 5"
>of pitch. Is that
>right? If so, how
>does one check for 6"
>pitch, for example?

The 3"-5" is a misprint, it should be 3" to 15".

If you don't want to get a gauge, an alternative is to make wedges out of plywood at fixed angles. To use it. put the prop on a flat table, and then slide the wedge until it's flush with the surface of the prop. You don't get evenly-spaced stations, but that doesn't really matter. I used this for years until I found out about the Prather gauge.

Alternately, it would seem to be very easy to make a gauge similar to the Prather. The trig is trivial, and the gauge would certainly be easy to construct using wood.

Brett

Ken Clapson · Mar 21, 2001 10:54 PM

#5 source

There is an Edmunds Pitch Gauge / model QM4010 at www.darrolcady.com/Propellers/propellers.htm

LNeumann · Mar 22, 2001 09:01 AM

#6 source

Now that you pointed that out to me, I just got off the phone talking to Greg Edmunds (He's a pylon racer, a modeler and knows our interests) about that pitch gauge. The Prather's are just non-existant these days. You can't get them. Gregg made one for himself out of frustration, and has since made short runs of 5 each for Darrol Cady to sell. But his, being made for a pylon racer, has only 12 stations, whereas the Prather has 14. I talked to him about extending it to where it could read a 13 inch or 14 inch prop. The cost is in the engineering, not the manufacturing, and, if we can get larger quantities, it might be doable. Let's face it, if you don't need that long of a prop, it will still work on the shorter blades. It is frustrating, however, wanting to read a longer prop and not being able to.

Greg, also, made a comment I have long suspected--the Prather gauges are not consistent one with another. When I hear some people quoting the pitch on their props, well, it doesn't compute if you do the numbers. All that could be explained by inaccuracies in the gauges. Since he works with precision machinery, his will be calibrated and accurate.

Anyone interested in obtaining one if they can be had? We are gong to follow up and crunch some numbers and see what can come out of this.

Leonard Neumann

Peter Hess · Mar 22, 2001 09:50 AM

#7 source

Thanks to Ken Clapson for his post about the Edmunds Pitch Gauge.
Leonard: Please count me among those who would be interested if you can get things worked out with Greg Edmunds. In the meantime, or if things can't be worked out with Greg Edmunds for an extended gauge, would the existing one be capable of handling a prop of a mere 12" diameter?
Please keep us posted.
Thanks!
Peter

kdheath · Mar 22, 2001 12:15 PM

#8 source

Leonard, put me on the list for one of these little gems, too.

LNeumann · Mar 22, 2001 01:14 PM

#10 source

Rather than everybody following up on the "Me Too" board, why don't you just e-mail me if you are interested in an extended pitch gauge.

If we get enough people to offset their R&D stuff, we ought to be able to bring it in at or around the Prather price, with the added width to accept longer props and at much greater accuracy as to the reading on the gauge.

And it will be available, which the Prather gauge isn't.

Leonard Neumann

Bob Reeves · Mar 22, 2001 12:54 PM

#9 source

Ok here goes the Me-to's

Me to!

Randy · Mar 22, 2001 08:15 PM

#11 source

Hi,

I made mine from a template that Jim Hoffman sent me. It was printed in MAN a LONG time ago. Made it from some 1/4" Mahogany I had laying around. Seems to work pretty well and looks cool. <grin>

Hey Len, Me Too!

Randy

Steve Helmick · Mar 22, 2001 09:14 PM

#12 source

IF that doesn't look economically feasible, how about a few of ya calling or emailing Terry Prather and see if he won't extend the pitch gauge and sell them? He was a NATS combat winner, ya know! Tell him about the growth in STUNT and how he's missing a big market, etc. To tell the truth, my Prather gauge needed a bunch of deburring and edge breaking to make it slide freely. I would suspect the silkscreening of the lines and numbers might be a source of error. I'm also concerned with the durability of the silkscreening, engraving would be much better. But I've got this one paid for. Steve

peabody · Mar 23, 2001 07:42 AM

#15 source

On the other board I quizzed about the possibility of using a helicopter pitch gauge on our stuff. They are less expensive, seem easy to use, and manufactured by folks who seem to really want to sell stuff.

I know that these vendors will be at Toledo. I won't.

They may be in Philly over the weekend. I'll check then.

See Ya

Peabody

Larry F · Mar 23, 2001 06:13 PM

#17 source

Brett nailed it. To make it even simpler, just use a carpenter's adjustable angle square, then read the degrees with a cheap protacter.

As Brett says, the trig is trivial. It is freshman high school, and is just a triangle with the degrees given, and the base of the triangle is pi * the diameter you are measuring from the hub. Any spreadsheet will convert that to inches of pitch in a heartbeat.

Nothing worse than $10 solutions for 10 cent problems.

Larry F

LNeumann · Mar 23, 2001 08:34 PM

#18 source

Bob worked up a spread sheet to do what you say that we can post for downloading on the web site...but...What you are proposing is a ten cent solution for a $100 problem.

Brett was correct in that the math is simple (if you went that far with math, that is.) And that makes it simple to draw up the face of the pitch gauge. But the pitch gauge is what is going to make it simple (simpler) to measure the prop and make changes as needed.

Doing what you propose, you still need some kind of fixture to hold the prop, some kind of method (or ruler) to determine the various stations, some kind of bar to measure the angle (your carpenter's adjustable angle square), some method to read the angle (your cheap protractor), and some method to deterimine the angle (or pitch) after you relate the correct angle, or fraction thereof, to the correct station (check the spread sheet, and if the number is not there, enter another number of interpolate).

All this will be done automatically by the pitch gauge. And then if I want to add a quarter of an inch of pitch across the blade, or just at the tips, I can do so with the gauge very quickly. Otherwise we have to recalculate everything every time.

Now a pitch gauge that can be locked into place could be useful for setting the pitch on our props. It would be helpful to be able to set the gauge at whatever station you were going to be setting (or measuring) at. Then you could heat the prop, set it down in the fixture (quickly) and twist it and hold it against the gauge while it cools. Some people can twist it by hand and get their desired change pretty close. Others of us like to use the gauge.

Leonard Neumann

Larry F · Mar 23, 2001 09:19 PM

#19 source

Leonard --

You made me laugh at myself in a way that I haven't for a few years. Our company had one of those "hug a buddy" outings several years ago where you bare your soul, soak naked with managers in hot springs, and I don't know what all. One of the things that came out was that I was a "control freak" with an odd twist. I never try to control people, but I always control data and the way it is collected. Guilty!!

Yeah, and you have the same problem. Either method works, you data control freak!

Larry F

Steve Helmick · Mar 30, 2001 01:27 AM

#20 source

Regarding pitch gauges, it appears to me that for stunt sized props, it is pretty much overkill using EVERY pitch station of a Prather gauge. I believe that if you doubled the distance from slot to slot, it would work fine and be more user friendly. The short racing and speed props would need the "fine tooth" base, not ours. Any disagreement? If you were trying to repitch carbon, glass or nylon/glass props with heat, would you consider making a plaster pattern so you could just heat the prop and lay it in the form, or maybe bolt it into the form and then heat it? Mr. B-17 used heat to adjust the pitch on his APC's for the 909, but I've never read about anybody else doing this on nylon/glass props. Seems interesting, especially since most prop manufacturers decrease pitch at the tip, wrong for our use. Steve

Brett Buck · Mar 30, 2001 02:17 AM

#21 source

>Regarding pitch gauges, it appears to
>me that for stunt sized
>props, it is pretty much
>overkill using EVERY pitch station
>of a Prather gauge. I
>believe that if you doubled
>the distance from slot to
>slot, it would work fine
>and be more user friendly.

Exactly so. I use only every other station most of the time.

>Mr. B-17 used heat to
>adjust the pitch on his
>APC's for the 909, but
>I've never read about anybody
>else doing this on nylon/glass
>props.

It works OK, although APCs take a lot more heat and force that your average graphite/epoxy, but it seems to stay pretty well. The one I fiddled with at the 94 NATs was still OK when I checked it about a year ago. Forget turning a 6" pitch APC prop into a 3.25, something that's relatively easy with a Bolly.

> Seems interesting, especially since
>most prop manufacturers decrease pitch
>at the tip, wrong for
>our use.

It probably means only that the pitch doesn't increase as much as we like. The effective pitch of every prop I have checked went up dramatically at the tips, one the airfoil is taken into account.

Brett

LNeumann · Mar 30, 2001 08:03 AM

#22 source

>Regarding pitch gauges, it appears to me that for
>stunt sized props, it is pretty much overkill using
>EVERY pitch station of a Prather gauge. I believe
>that if you doubled the distance from slot to slot,
>it would work fine and be more user friendly.
>The short racing and speed props would need the
>"fine tooth" base, not ours. Any disagreement?

You are correct here. For fine tuning you can heat and twist at the hub and check at one point and probably be OK. We check at three points to see where we are at--close to the hub, somewhere in the center, and close to the tip. For wood props, checking at every station or every other station might be more beneficial since these can be fine tuned by sanding. And for the speed guys, as you say, well, if you are making the pitch gauge, you may as well make it so it can accomodate the greatest number of people. the cost doesn't go up machining the additional slots or silkscreening (lazer cutting?) the dial. It is a numbers game. Volume sales would lower costs.

Leonard Neumann

Steve Helmick · Apr 01, 2001 07:42 PM

#23 source

Most of us know about the Hooptee pitch gauge article that John Kilsdonk published in Model Aviation in ??? I saw a picture of John in Stunt News recently, so it occurred to me that maybe with a prod or two, John (or somebody else?) could be persuaded to revise the Hooptee gauge, extending it for 16" diameter props (?!) and publish it again in either MA (editor being our man Bob Hunt) or Stunt News (wouldn't pay as well). Anybody know Mr. Kilsdonk, please twist his arm! Steve

bkruger · Apr 02, 2001 12:00 PM

#24 source

LAST EDITED ON Apr-02-01 AT 12:27 PM (EST)

LAST EDITED ON Apr-02-01 AT 12:18 PM (EST)

>Most of us know about the
>Hooptee pitch gauge article that
>John Kilsdonk published in Model
>Aviation in ??? I

>Anybody know Mr. Kilsdonk, please
>twist his arm!
>Steve

Steve;

No arm twisting was necessary. Ed Ruane was kind enough to scan his copy and send it to me. When I saw that John was the author of the article, I emailed him and asked him if he had a clean paper copy. John very generously sent me a crisp paper copy of the article. My intent is to CAD it and make it available to anyone who wants.

John and Ed are real gentlemen. People like them make this hobby/obsession so enjoyable.

If you are anyone else want a copy of John's article, I will be more than happy to burn it and drop it in the mail. Just email me at [email protected].

After looking at John's gauge, though, I had another idea to simplify the gauge itself. The way that John's gauge is constructed, and most of the commercial ones, is that you visually cross reference the indicated pitch of the blade on a similar mark on the side of the scale. This to me is a little imprecise, albeit very convenient. It allows for distortion during the manufacturing and copying process, plus induced error from the observation process during an actual check.

My idea to do this involves similar construction to John's, but readout comes from the intersection of the pivoted straightedge with a protractor. This would give a precise angle which could be then easily cross referenced on a chart to give the pitch for the specified radius. I've already done the spreadsheet to generate the chart. Pat Johnston (ever generous and helpful) sent me a CAD protractor that some folks use for timing wheels. Crist Rigotti send me a .pdf of a protractor. I haven't figured out how to make either look decent on the side of the gauge. If all else fails, I may head over to Office Max and glue a 99 cent protractor on the side of the #$%^&* thing.

Regards - Bob Kruger

Steve Helmick · Apr 04, 2001 11:33 PM

#25 source

Shoot, all you'll have to do is send the CAD file on a disc to Tom Morris along with a 500 word essay. You can do that with your toes. We liked your article on Chicken Hopper tanks, and we'll look forward to seeing the pitch gauge in Stunt News! Don't forget to stretch it out for bigger props for those Saito .91 4-strokes.

Steve