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Maihak Steam Engine Indicator Thread Adapter

gcg2

Plastic
Joined
Jun 7, 2022
Hello all - I recently purchased a Maihak 50Z indicator; being new to indicators, I did not know the size of the nut that threads onto a valve - and it did not include a valve. The Corliss steam engine I'd like to try this on has a ball valve (1/2" and inside-threaded, I believe) on the indicator piping, so I was not concerned about purchasing an indicator with a valve included - I figured I could solder up an adapter from off-the-shelf plumbing aisle parts. Little did I know, until after receiving the indicator and then reading the thread on this forum, from 11/19/2017 "OT: A tale of a steam engine indicator" and a post from Joe Michaels, that my indicator likely has 27MM x 1/10" threads. Joe mentioned making an adapter.

So my question is, can I build an adapter, and where would I find the fitting needed for the Maihak end. I see that Leutert sells valves but since the engine has one, and I expect purchasing a valve would be quite expensive, I'd like to try to make something. Any advice would be appreciated.

Thanks,
Gary
 

L Vanice

Diamond
Joined
Feb 8, 2006
Location
Fort Wayne, IN
If you want to cut a 27 mm x 10 TPI thread, then most of the engine lathes in The USA and many other countries can do it. You did not supply your location. The 27 mm dimension (1.063 inch) can be cut on about any lathe, whether inch or metric.

No lathe? Then it gets tricky, but taps and dies can at least let you avoid single-pointing the thread. You did note that 27 mm is practically the same as 1-1/16 inch, right?
You can buy a 1-1/16-10 tap at Victor. https://www.victornet.com/detail/TAST-1-1/16-10.html
You can buy a 1-1/16-10 die from Victor. https://www.victornet.com/detail/RD-1-1/16-10-E.html

Larry
 

Joe Michaels

Diamond
Joined
Apr 3, 2004
Location
Shandaken, NY, USA
Hello all - I recently purchased a Maihak 50Z indicator; being new to indicators, I did not know the size of the nut that threads onto a valve - and it did not include a valve. The Corliss steam engine I'd like to try this on has a ball valve (1/2" and inside-threaded, I believe) on the indicator piping, so I was not concerned about purchasing an indicator with a valve included - I figured I could solder up an adapter from off-the-shelf plumbing aisle parts. Little did I know, until after receiving the indicator and then reading the thread on this forum, from 11/19/2017 "OT: A tale of a steam engine indicator" and a post from Joe Michaels, that my indicator likely has 27MM x 1/10" threads. Joe mentioned making an adapter.

So my question is, can I build an adapter, and where would I find the fitting needed for the Maihak end. I see that Leutert sells valves but since the engine has one, and I expect purchasing a valve would be quite expensive, I'd like to try to make something. Any advice would be appreciated.

Thanks,
Gary
 

Joe Michaels

Diamond
Joined
Apr 3, 2004
Location
Shandaken, NY, USA
I will get into my shop in the next couple of days and re-measure the Maihak indicator adaptor threads & mating taper. Here is food for thought regarding the Maihak indicator threads: Germany as well as other European and even the Japanese, have had a habit of playing 'mix-n-match' with pipe threads. It was quite common for the Germans to use British Straight Pipe & British tapered pipe threads while all else was metric. I ran into this with powerplant equipment made in Germany, Switzerland, and Japan many times.

My guess is we are seeing what may well be a British Straight Pipe Thread on the indicator union connection. 27 MM works out to a hair under 1 1/16" (1.0611" in actuality when doing the metric conversion). 3/4" pipe has an outside diameter of 1.050". Difference in diameters is 0.011". 10 threads to the inch may not be BSP, but may be a common enough 'inch pitch' thread used in otherwise metric countries. Another example of this is the threads on the receivers and barrel shanks of the German Mauser Model 98 rifles. 50 + years ago, when I was an undergraduate engineering student, another student and I got into building a few rifles on the 98 Mauser actions. I was working part time in a machine shop, so was the likely guy to get into this project. Back then, 98 Mausers were available quite cheaply, and parts were readily available as well. We got hold of some 98 Mauser military rifles and proceeded to remove everything from the receivers and started from there. I was pleasantly surprised to find the Mauser barrel shanks were threaded with an 'inch pitch' (12 threads/inch if I remember right). I wondered why a German military rifle would be designed with an 'inch pitch' on the thread of the barrel shank/receiver. Years later I found out: Paul Mauser had come to the USA to try to sell his design for the rifle and had worked with one of the US firearms manufacturers on some prototypes, with the result being a barrel threaded with an 'inch pitch' (my term) rather than a metric pitch. I happily chucked Douglas barrel blanks into a Lodge and Shipley engine lathe and machined and threaded them to fit the Mauser actions, no metric lathe needed. Over the years I have done engineering work on some Swedish steam locomotive boilers and seen engineering drawings of German steam locomotive boilers. What was quite common was the use of Whitworth/inch sized threads on boiler staybolts, as well as British pipe threads on the boiler fittings. It was 'mix n match'. Similarly, every so often, a post will appear on this 'board about an old German made screw cutting lathe. These often have both inch and metric systems for thread cutting on the change gear data plates. Even vernier calipers bearing the Wehrmacht stamp from WWII will often have dual measurement systems, inch & metric.

It's been awhile since I machined that adaptor, and, unfortunately, I never kept any sketches of it. I know I matched the taper on the Maihak indicator's half union. My method started with rough measurements to get the taper attachment 'into the ball park' for first setting, and then 'machining a dummy' and bluing it in to confirm I had the correct taper setting.

Gary: Where are you and that Corliss engine located ? Is it a museum engine or a working engine ?
 

L Vanice

Diamond
Joined
Feb 8, 2006
Location
Fort Wayne, IN
.... 27 MM works out to a hair under 1 1/16" (1.0611" in actuality when doing the metric conversion). ...
Joe, I divided 27 by 25.4 to get 27 mm = 1.06299 inches. I used the calculator function on my computer. I tried some other online converters and got the same answer.

How did you get 27 mm = 1.0611 inches? Your slipstick does not do that many decimal places unless it is awfully long. I have forgotten how to use log tables, but I bet they give the same result as my calculator.

Larry
 

Joe Michaels

Diamond
Joined
Apr 3, 2004
Location
Shandaken, NY, USA
Larry:

I used 0.0393" = 1 mm , a conversion that I carry around in my head. 27 mm x 0.0393"/mm = 1.0611" on my TI-36X calculator. OK, now just for fun, I am getting my old (1963) K & E Log-Log Duplex Decitrig slide rule out of the desk, this has 10" long scales. My eyes ain't what they used to be, so am using a jeweler's loupe to make sure I line up the numbers.... I get 1.062" on the old slip stick. That is with a bit of visual interpolation of where the hairline cuts the C scale. It's been ages since I last used the slipstick, thanks for getting me going with it again. I've spent a few hours at my drawing table today, detailing up framing plans for a large deck. Structural jobs come in to me at the rate of about 2-3 a week, requiring my services as a Professional Engineer. Since this covid pandemic hit, we are seeing a huge migration of people from NYC buying up everything and anything in the way of real estate around here, paying stratospheric prices for it, and pouring even more money into developing previously 'undevelopable' land, or decrepit houses with rebuilds, additions, and renovations. Some jobs top 1 million, and one addition to an existing second home is running a bit north of $ 750K. Some jobs are so big and the owners want impossibly wide clear spaces that I am detailing structural steel used in conjunction with engineered lumber or salvaged heavy timber framing.
I am running calculations pretty steadily, so the TI 36X is what I use. My drawing table dates to about 1900, with a new top on it, and has a Vemco drafting machine with Dietzgen scales. I have the old green 'lead pointer' and use the Stadler 'clutch' (collet) type 'lead holders'. It's hand lettering and old style drawing. K & E "paragon" drafting instruments, Dietzgen architect's and engineer's scales... It felt good to unlimber the slip stick after a day of running numbers and drawing. Normally, I work with designers who are unlicensed, and I hand them rough sketches with structural members figured. They, in turn, produce CAD drawings which I review, stamp, and those are used to get the building permits and as working drawings. In this case, a contractor who was not setup for CAD had an ongoing job at a wealthy client's place, kind of a never-ending string of work. He asked me to design and draw up the deck. Ordinarily, for complete house plans and similar, it is neither cost-effective nor would I even have the time to spend drawing up complete sets of plans 'on the board'. About the only times I do any real drafting are when it's a job involving steel fabrication, machinery, piping, or an occasional septic system job (which is also a good exercise for me to take out my Brunson transit and do some field work). Old school, I guess.

I have two planimeters in my office, one came from you, as did my Maihak indicator. My other Maihak indicator came off a Uniflow powered steam vessel, so does not have springs with the right pressure ranges/scales for use on lower pressure steam engines. The Maihak indicator you sold me (ex US Army Engineer Corps) will get used this season at Hanford Mills, as will the planimeter.

While I truly enjoy 'practicing engineering', and truly enjoy turning out a nice-looking engineering drawing, I am realistic enough to know when CAD is the way to go. Not setup for CAD and not of a mind to learn it, so work with people who have it at their fingertips. My Italian grandpa (a whole other story) had plenty of little life lessons he imparted to me when I was a boy. One story he used to tell was 'Ever'body eats macaroni'. It was a story about how a priest in the old country was given a sum of money to have a chapel or some other structure built for the local church. The priest put the word out and the local contractors all made their proposals. The winning bidder was a bigger contractor. Instead of doing all the work with his own resources, he subbed most of it out, giving pieces of the job to the other guys who had not submitted the winning bid, or simply were too small to have bid the job. As he told it, even guys who had nothing more than strong backs were put to work as laborers, and men with draft animals were hired to haul materials or draw sand and gravel from banks and haul it to the jobsite. As a result, 'ever'body eats macaroni', meaning the winning bidder shared the job and everybody made something from it. I follow that adage and call my friends when a job lands in my lap, subbing out steel fabrication, CAD work, referring work to friends who are excavating or general contractors, and similar. I work on a handshake, and I give a hard money price which I call my 'win, lose or draw' price. If the job takes a bit more work on my part, or there is need for me to come on site to inspect or explain the work, no extra charge. I work on a sliding scale, and if a person is a local who is not in the best of financial straits, I'll take a handshake and maybe a pickup load of cordwood and call it even. It's an oldtime way of doing business, and a lot is done on the strength of a person's word and a handshake. A drawing table, slide rule, and all else seem to go nicely with it. A 'Dazor" fluorescent lamp from the 50's lights my drawing table, and an ancient shop stool with a square-threaded screw to adjust seat height is at the table for me. I get asked to make parts for construction and logging equipment, to do welded repairs, to make parts for all sorts of things, and then to do work as a PE or Certified Welding Inspector. It's as good a way to spend 'retirement' as there is for me. I cannot see myself sitting on some huge floating hotel/resort (aka cruise ship) with forced gaiety and being part of a herd of tourists, nor have I ever hit a golf ball in my life and follow no sports whatsoever. I'm recovering from hernia repair surgery, done a little over a week ago. The result is I am on light duty for the next few weeks. The surgeon and I got on famously, and he had to do an open procedure. I kidded that I am getting to look like an old ship's hull or old locomotive boiler with surgical scars from the cancer surgery and now this hernia repair. Flying the old drawing board is about as safe a bet for me right about now as there is.
As for the hernia, I had it for some years, but it was small and not a problem. After the cancer surgery in March of 2021, I got to feeling so good that I started really catching up on overdue projects. Wife wanted a light fixture, I designed and built it for us. I had to put a 12" Bridgeport rotary table onto the Bridgeport to make the 'center hub' of the light fixture. To get the rotary table to where I could pick it with a chain hoist to get it onto the Bridgeport, I dead lifted the rotary table and lugged it over to the hoist. I suspect this put the hernia over the edge. Surgery was a breeze, and I left the hospital the same day, singing "It's a Long Way to Tipperary". Calculations, drawing, and engineering are great ways to follow doctor's orders for the recovery. I also found that wearing a clean pair of bib overalls (post-op instructions were not to wear pants with belts or other constrictive garments) are the ideal thing. I spent the first few days with freezer packs inside the front of my bibs while doing engineering work. The surgeon and the OR people used some kind of blue prep solution to paint my belly and groin with, so the operative site looked like they used Dykem Blue. Gotta love it. I'll get down to the shop in the next day or so and measure the Maihak indicator's union threads and taper.
 

L Vanice

Diamond
Joined
Feb 8, 2006
Location
Fort Wayne, IN
Joe, .03930 inch/mm is too approximate in this instance. If I need approximate conversions, I just use 1 mm = .04 in my head. Any real precision work gets the calculator treatment and the exact 25.4 mm to 1 inch figure. The other actual, but not quite exact, conversion figure is .03937 inch/mm. So 27 x .03937 = 1.06299, same as 27/25.4, and noticeably closer to 1-1/16 (1.0625) inch than 1.0611. That is why I said a 1-1/16-10 tap or die would practically fit a 27 mm x 10 TPI thread.

Getting old is interesting, but still better than the alternative. I had my hernia surgery in 2019 and bilateral carpal tunnel release this year. The tiny scars are no longer visible.

Stay well.

Larry
 

tdmidget

Diamond
Joined
Aug 13, 2005
Location
Tucson AZ
I will get into my shop in the next couple of days and re-measure the Maihak indicator adaptor threads & mating taper. Here is food for thought regarding the Maihak indicator threads: Germany as well as other European and even the Japanese, have had a habit of playing 'mix-n-match' with pipe threads. It was quite common for the Germans to use British Straight Pipe & British tapered pipe threads while all else was metric. I ran into this with powerplant equipment made in Germany, Switzerland, and Japan many times.

My guess is we are seeing what may well be a British Straight Pipe Thread on the indicator union connection. 27 MM works out to a hair under 1 1/16" (1.0611" in actuality when doing the metric conversion). 3/4" pipe has an outside diameter of 1.050". Difference in diameters is 0.011". 10 threads to the inch may not be BSP, but may be a common enough 'inch pitch' thread used in otherwise metric countries. Another example of this is the threads on the receivers and barrel shanks of the German Mauser Model 98 rifles. 50 + years ago, when I was an undergraduate engineering student, another student and I got into building a few rifles on the 98 Mauser actions. I was working part time in a machine shop, so was the likely guy to get into this project. Back then, 98 Mausers were available quite cheaply, and parts were readily available as well. We got hold of some 98 Mauser military rifles and proceeded to remove everything from the receivers and started from there. I was pleasantly surprised to find the Mauser barrel shanks were threaded with an 'inch pitch' (12 threads/inch if I remember right). I wondered why a German military rifle would be designed with an 'inch pitch' on the thread of the barrel shank/receiver. Years later I found out: Paul Mauser had come to the USA to try to sell his design for the rifle and had worked with one of the US firearms manufacturers on some prototypes, with the result being a barrel threaded with an 'inch pitch' (my term) rather than a metric pitch. I happily chucked Douglas barrel blanks into a Lodge and Shipley engine lathe and machined and threaded them to fit the Mauser actions, no metric lathe needed. Over the years I have done engineering work on some Swedish steam locomotive boilers and seen engineering drawings of German steam locomotive boilers. What was quite common was the use of Whitworth/inch sized threads on boiler staybolts, as well as British pipe threads on the boiler fittings. It was 'mix n match'. Similarly, every so often, a post will appear on this 'board about an old German made screw cutting lathe. These often have both inch and metric systems for thread cutting on the change gear data plates. Even vernier calipers bearing the Wehrmacht stamp from WWII will often have dual measurement systems, inch & metric.

It's been awhile since I machined that adaptor, and, unfortunately, I never kept any sketches of it. I know I matched the taper on the Maihak indicator's half union. My method started with rough measurements to get the taper attachment 'into the ball park' for first setting, and then 'machining a dummy' and bluing it in to confirm I had the correct taper setting.

Gary: Where are you and that Corliss engine located ? Is it a museum engine or a working engine ?
Joe, those Mauser barrels are 12 tpi Whitworth profile. the debate over the strength of Whitworth threads may never be settled but for some it was never a question.
 

gcg2

Plastic
Joined
Jun 7, 2022
If you want to cut a 27 mm x 10 TPI thread, then most of the engine lathes in The USA and many other countries can do it. You did not supply your location. The 27 mm dimension (1.063 inch) can be cut on about any lathe, whether inch or metric.

No lathe? Then it gets tricky, but taps and dies can at least let you avoid single-pointing the thread. You did note that 27 mm is practically the same as 1-1/16 inch, right?
You can buy a 1-1/16-10 tap at Victor. https://www.victornet.com/detail/TAST-1-1/16-10.html
You can buy a 1-1/16-10 die from Victor. https://www.victornet.com/detail/RD-1-1/16-10-E.html

Larry
Larry - thank you for the links to the tap and die, this gives me an option; I do not have access to a lathe that would cut this.
 

gcg2

Plastic
Joined
Jun 7, 2022
Joe, those Mauser barrels are 12 tpi Whitworth profile. the debate over the strength of Whitworth threads may never be settled but for some it was never a question.
Thank you, Joe. I am located in central PA; this is for a circa-1900 Corliss that we run during our antique machinery shows. I thought it would add interest to demonstrate an indicator on the engine. A friend suggested I contact Leutert ( whose current data sheet on a type 50 shows it as a W 27 x 1/10" ) to see if they sell an adapter; I contacted them just to see what they say.
-Gary
 

Joe Michaels

Diamond
Joined
Apr 3, 2004
Location
Shandaken, NY, USA
Hello Gary:

I got into my shop and measured the adapter I made for the Maihak indicator. I discovered I had made two (2) adaptors, as there was some difference in dimensions on the male taper of the 'half union' on each of my two Maihak indicators. Here are the dimensions:

thread (common to both models of indicator): 1.062" diameter x 10 threads/inch x 0.630" long.

Body: 1 5/16" outer diameter (one adapter made of bronze, one of stainless steel), 3/4" NPT female tapping for connection to indicator piping

Taper: female, approx 0.772" on large end, 0.619" deep, approx 6 degrees 30 min included angle (this on the taper for the older Maihak indicator which will be the
one I use). I got the taper with my Starrett vernier bevel protractor and a 1-2-3 block, measuring down one side of the female taper on the adaptor I made. This is as close a measurement of the angle of the female taper as I could make. I still see some of the Prussian blue where I did 'blue in' the adaptor to the male taper on the indicator half union.


I am glad to read that you will be taking a set of cards on the Corliss engine. One thing I learned ages ago: a card taken on an engine with variable cutoff, running without load will produce a 'skinny' diagram as cutoff is way early. With load on that same engine, the card gets to resembling 'the foot' (like a person's foot viewed from the side). This 'foot shaped' (0r approximately so) diagram will be a bit easier to read and get the MEP from.

As far as Leutert and an adaptor: I'd be wary of what they have available nowadays. My reason for saying this is because Leutert now furnishes indicators solely for indicating slow speed diesel engines, with much higher pressures. An indicator cock on a diesel engine usually has a much smaller flow passage for its size than a steam engine indicator cock. Leutert was helpful to me when I contacted them, and sent me a few packs of indicator cards and some stylus points gratis. However, they did not have any information nor could they furnish springs of lower pressure ranges for the higher pressure instrument used on the Unaflow marine engine.

Matching the taper so the adaptor mates up and makes a steam-tight joint is more critical than the screw threads, which can be cut a little on the loose side.
 

gcg2

Plastic
Joined
Jun 7, 2022
Thank you, everyone, for the great assistance. I have a few options to look at, now.

So Leutert referred me to Kiene Diesel with regard to purchasing a valve or adapter. https://www.kienediesel.com/pdf-large-bore/EUROPEAN-TYPE INDICATOR VALVES.pdf shows a 1 1/16-10 Whitworth (W27 X 1/10”) valve, but as Joe mentioned, the diagram does show a small passageway. Interesting that they also call it 1-1/16", as Larry did earlier in this thread.

The Corliss runs without load, on only about 80lbs, and at only 12-20RPM (yup, just so folks can see it turn) - and being that my indicator only came with two springs, which may be too stiff to work at this pressure, I may have to make some guesses at off-the-shelf springs that might allow the indicator to register. Being that it is only for demonstration, I am hoping this would give folks an idea of what the indicator does. I also need to build either a pantograph or reducing wheel. Good to know that I should expect a 'skinny' diagram - that makes sense. Audel's Engineers and Mechanics Guide 3 contains a chapter on indicators, and I have an electronic copy of the book entitled, "The Steam-Engine Indicator" copyright 1900, by Peabody. These should help in designing a pantograph if I go that route.

There is at least one machine shop close by, so I will see what it would cost me to have something made; thanks, Joe for the dimensions. To go the die route I'd have to buy two - one for NPT and, of course, the W27, then somehow get the inside taper right - and being that I am not a machinist, I'm not sure I could make this accurately enough in my shop.

-Gary
 

L Vanice

Diamond
Joined
Feb 8, 2006
Location
Fort Wayne, IN
That is the first mention of Whitworth in describing the indicator threads. It means the thread form is 55 degrees instead of 60 degrees, so the Victor tap and die, which are 60 degree, will not produce a good mating thread for the Whitworth threads in the indicator. They will still screw together, but there will be some damage to the threads it the parts are tightened very much. Whitworth threads can easily be cut on a lathe by using a tool of the correct shape.

Larry
 
Last edited:

Joe Michaels

Diamond
Joined
Apr 3, 2004
Location
Shandaken, NY, USA
Gary:

Thanks for the reply, and I am glad we are able to be of some help to you. If you do work with a machine shop to make the adaptor, having the indicator on hand would be helpful in matching the taper of the union. As I posted, I got a measurement on the female taper on the adaptor I made, but would not consider it as precise enough for making a steam-tight connection. The machine shop will need the indicator to try the adaptor onto and check the fit of the mating parts with chalk or Prussian Blue.

I held back from suggesting Kiene as a source of indicator cocks and adaptors, having knowledge of them from medium & slow speed diesel engine work. Kiene's most popular instrument is likely their diesel firing pressure indicator, which registers peak or firing pressure in an engine's cylinder. With the kind of temperatures and pressures in that application, the Kiene fittings typically have rather small drilled flow passages. Whether Kiene uses the same taper for the unions on their instruments as Leutert (Maihak) would also have to be determined. Possibly, if Kiene's fittings matched up in terms of screw threads and taper for the union connection, the flow passage could be drilled out larger. I believe anything Kiene makes will be made of alloy steel to stand up to the gases shot out the indicator cock on a diesel engine. Steam engine indicator fittings were usually made of brass or bronze, but that was in the 'pre stainless steel' days. At least on my Maihak indicator, the union's male taper is made of bronze. I'd suggest making an adaptor out of bronze as well, preferably something softer like 660 bearing bronze. Less chance of deforming or damaging the male taper on the indicator.

A pantograph is about the simplest form of reducing motion for an indicator. On a slow turning engine like a Corliss, a pantograph will work well. Pantographs were often made of light pieces of hardwood, easy to work with and lower inertia than steel parts. My own idea for a reducing motion to indicate the higher speed (200 rpm) engine at Hanford Mills is a takeoff on the 'differential pulley' mechanism. I have the idea of using a salvaged recoil starter from a Honda (0r Honda clone) engine as it provides ample travel to accomodate the 12" stroke of the engine and has a fairly large rope sheave. A smaller rope sheave on the business end of the recoil starter would then be used to work the indicator cord. The clockspring in a recoil starter will maintain tension in the cord from the crosshead of the engine to the sheave in the recoil starter, a feature the old reducing mechanisms usually had. Call it backwoods engineering.

Larry: I will admit to taking the easier route as far as thread cutting. I figured the thread was likely a metric form, since the instrument was German made, so used a 60 degree threading tool. My own mental ramblings about Germans using British Standard Pipe threads should have kicked in back when I machined the adaptor. As you note, the 60 degree form male thread I cut on the adaptor does make up OK with the female thread on the indicator. Now you have me thinking I need to buy a Whitworth center gauge and grind a Whitworth form tool... and make another adaptor or two. Someday when the snow is deep outside and other projects are caught up, I guess.

As a student at Brooklyn Technical HS (1964-68), we were acquainted with the different thread forms and thread systems. We were shown a profile drawing of the Whitworth thread, and our machine shop and mechanical drawing teachers discussed thread forms with us. We were told that "the Whitworth is a better and stronger thread" than the Unified Form 60 degree thread used in the USA. We were also told that the Whitworth thread had some limited use in the USA, but never explored the Whitworth thread beyond those cursory remarks.
 

gcg2

Plastic
Joined
Jun 7, 2022
Gary:

Thanks for the reply, and I am glad we are able to be of some help to you. If you do work with a machine shop to make the adaptor, having the indicator on hand would be helpful in matching the taper of the union. As I posted, I got a measurement on the female taper on the adaptor I made, but would not consider it as precise enough for making a steam-tight connection. The machine shop will need the indicator to try the adaptor onto and check the fit of the mating parts with chalk or Prussian Blue.

I held back from suggesting Kiene as a source of indicator cocks and adaptors, having knowledge of them from medium & slow speed diesel engine work. Kiene's most popular instrument is likely their diesel firing pressure indicator, which registers peak or firing pressure in an engine's cylinder. With the kind of temperatures and pressures in that application, the Kiene fittings typically have rather small drilled flow passages. Whether Kiene uses the same taper for the unions on their instruments as Leutert (Maihak) would also have to be determined. Possibly, if Kiene's fittings matched up in terms of screw threads and taper for the union connection, the flow passage could be drilled out larger. I believe anything Kiene makes will be made of alloy steel to stand up to the gases shot out the indicator cock on a diesel engine. Steam engine indicator fittings were usually made of brass or bronze, but that was in the 'pre stainless steel' days. At least on my Maihak indicator, the union's male taper is made of bronze. I'd suggest making an adaptor out of bronze as well, preferably something softer like 660 bearing bronze. Less chance of deforming or damaging the male taper on the indicator.

A pantograph is about the simplest form of reducing motion for an indicator. On a slow turning engine like a Corliss, a pantograph will work well. Pantographs were often made of light pieces of hardwood, easy to work with and lower inertia than steel parts. My own idea for a reducing motion to indicate the higher speed (200 rpm) engine at Hanford Mills is a takeoff on the 'differential pulley' mechanism. I have the idea of using a salvaged recoil starter from a Honda (0r Honda clone) engine as it provides ample travel to accomodate the 12" stroke of the engine and has a fairly large rope sheave. A smaller rope sheave on the business end of the recoil starter would then be used to work the indicator cord. The clockspring in a recoil starter will maintain tension in the cord from the crosshead of the engine to the sheave in the recoil starter, a feature the old reducing mechanisms usually had. Call it backwoods engineering.

Larry: I will admit to taking the easier route as far as thread cutting. I figured the thread was likely a metric form, since the instrument was German made, so used a 60 degree threading tool. My own mental ramblings about Germans using British Standard Pipe threads should have kicked in back when I machined the adaptor. As you note, the 60 degree form male thread I cut on the adaptor does make up OK with the female thread on the indicator. Now you have me thinking I need to buy a Whitworth center gauge and grind a Whitworth form tool... and make another adaptor or two. Someday when the snow is deep outside and other projects are caught up, I guess.

As a student at Brooklyn Technical HS (1964-68), we were acquainted with the different thread forms and thread systems. We were shown a profile drawing of the Whitworth thread, and our machine shop and mechanical drawing teachers discussed thread forms with us. We were told that "the Whitworth is a better and stronger thread" than the Unified Form 60 degree thread used in the USA. We were also told that the Whitworth thread had some limited use in the USA, but never explored the Whitworth thread beyond those cursory remarks.
Good to know a pantograph should be appropriate. I really like the idea of using a salvaged recoil starter; I will keep that in mind if the pantograph doesn't work out. I'll mention Whitworth and 660 bearing bronze to the local machine shop. If getting the part machined turns out to be a higher cost than I want to pay, there may be someone in our antique machinery organization that could machine the part too. We are anticipating getting a VERY old Putnam lathe, however the current owner said it would not be able to do this job.

Gary
 








 
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