Member postings for Martin Johnson 1

Thanks for all the responses.

Mark - yes it is probably running too slow, but it is direct on a 2800 rpm grinder, so cannot be changed very easily.

Douglas - yes 2 thou is getting on but I was modifying a milling cutter, so had quite a lot to chew off.

As for the rest, you are confirming what I had hoped that diamond for HSS is not theoretically right, but it seems for light hobby use it is OK.

Off to scan ebay and Arc Euro then......................

Thanks all,

Martin

Just another thought. Did you check for run out on the test bar when the spindle is rotated? Should not be any on a brand new lathe and test bar, but if there is do your checks at 180 degree rotations of the spindle and split the difference.

Martin

The "Twist the bed until it turns parallel" school of thought originated in parts of Nottingham. But it is poor way of making up for a lightweight flexible bed.

However, better quality lathes should have sufficient stiffness in their own bed. The instructions for my Kerry say to undo the bed holding down bolts to finger tight only, and it is supported on wooden shims to let the bed find it's own level. Clearly the orientals think the same way if it your lathe has a 3 point mounting.

That being so, you need to contact your supplier and send the photos you have posted here. If anyone has an older lathe with similar problems, you may well find an adjuster under the headstock which will allow the headstock to be rotated on the bed by a tiny amount. (The Kerry has such a device). Use with care, because you also need the lathe to face off very slightly concave (about 0.001 in 10" diameter or so).

Hope that Helps,

Martin

Well, after many years I have lashed up a tool & cutter grinder, own design using bits of worden, stent, quorn all re-arranged to suit me.

Anyway, I purchased a 4" white cup wheel (no markings at all so probably Chinese s**t) from one of the usual suspects which seems very soft. Dressing it produces ridiculous amounts of grit all over the shop. Even taking grinding cut of a couple of thou can produce more clouds.

I am trying to keep the T & C grinder in the machine shop to avoid rust. I could put it in the welding / grinding area but that is very prone to rust. Carrying it to and fro for wheel dressing is possible, but hard work.

I have been thinking about changing to a diamond / cbn wheel (Arc Euro & others do them). Obviously great for carbide tooling, but what about using them on HSS?

Seems to me it would cut out the clouds of grit when dressing problem. Anyone have any experience good or bad?

Many thanks,

Martin

If you are working in larger scales with a 3 cock gauge glass set, I was taught to do the hydraulic test with the glass isolated and the glass drain cock open so it cannot be pressurised. Obviously not an option with only drain cock.

I have 2 full size glasses break in service, one when I was in the cab. Not much fun, fumbling around to find the isolating cocks in a cloud of steam. At the time we couldn't get (afford) the proper glass seals so were "improvising" - hence the breakages.

Martin

Just realised that the link in my last post only takes you to the one photo. Scroll down the page and go the album, and the screw milling is toward the end of the album.

Martin

I am in the (very extended) course of doing a similar thing. My thread started as 0.75" pitch, 4 start 1" OD but has become 0.6" pitch, 3 start, 1" OD - it is for a steering box and I decided for other reasons to give the box more ratio. I decided to go down the thread milling route and have done the job on my TS mill. I am using a modified gear cutter (No. 1 which is near to rack form) to cut an ACME form thread. The nut (which I think is the more difficult job) is to be cast in whitemetal inside a bronze housing. There are some pictures on Flickr starting here:

https://www.flickr.com/photos/140734312@N06/37334008234/in/album-72157669955074511/

Hope that helps.

Martin

I can add another member to the "stone a zero rake flat" school of thought. Only needs a tiny flat; one of those diamond files or laps will do the job in seconds, then there is less to grind out if you need the same drill for steel.

There is another point though - plan the job so you avoid opening up holes, especially if you are opening up by a small amount. For small holes a pilot drill is a waste of time, and for large holes keep any pilot hole SMALL.

For drilling mating parts, drill the bolted part clearance, clamp parts together and just dimple through with the clearance drill. Dismantle, then drill tapping size starting into the dimple.

Martin

"I only finished making a second set of traction engine hub caps in cast iron the other week, after I was told, on another forum, that gunmetal wasn't prototypical. Now I wonder who it was that pointed it out to me?"

Who that man could be I just don't know! Hope you haven't really made a second set.

Glad some of my "eternal truths" have raised a laugh.

Best wishes to all for the New Year - when heads will be out of the drawings and brains and eyes will be engaged.

Martin

Did you know…………….

• The Caledonian Railway painted all their dock shunters in lined out passenger livery.
• Boiler fittings must (by law) be painted signal red.
• Tufnol is the only known thermosetting thermoplastic, which is why it can be shaped in boiling water to make spring leaves.
• All coupling rods are fluted at the back.
• All traction engines have brass hub caps on all four wheels and a copper or brass capped chimney.
• An exhibition judge instinctively knows more about the prototype of your model than you have found out in years of research.
• Cast iron swarf is so abrasive it will wear out lathe beds in a matter of days. Steel swarf has no such characteristic. Emery cloth abrasive similarly loses it’s properties on contact with a lathe bed.
• Grinding dust of micron size can be kept away from lathe beds by randomly scattered sheets of paper (never rag!).
• The utility of a Tool & Cutter grinder can be determined by the formula:

Utility = Number of Ball Handles x Number of felt lined mahogany accessory chests

• Tool and cutter grinders must include a 1” pitch screw. No other pitch will do.
• All internal combustion engines start for their designers after just a few pulls on the flywheel or propellor.
• All new locomotives designs have enough steam to remove the electric sucker after 30 seconds, full steam pressure after 5 minutes and will then do 10 laps of the track pulling 8 adults without any problems on their very first outing.
• Scrap boxes (except mine) always contain exactly the right item to build any given project.
• A Number 70 drill can be poked through a bit of 3/8” brass rod to make an injector cone on any old lathe.
• The amount of coal remaining in a firebox after a half hour run can be estimated to 4 decimal places of accuracy.

Don’t take it all too seriously………..

Happy Christmas.

Alan,

Before you give up, do talk to your local Occupational Therapist and Physiotherapy team. And make sure you give it time. You might also ask to be referred to your local REMAP panel via your Occupational Therapist.

Sadly with anything NHS you have to shout loud to get the attention - but do please shout.

Best Wishes,

Martin

Used to work for a company that made quarry equipment, although I was not closely involved with that side of the business. However, what you seem to have is:

A rod or ball mill right at the top, but I can't see just how it is fed.

A rotating screen (taking the output from the mill) depositing 3 sizes of sieved material into hoppers below. It looks like there is vehicular access under the hoppers, which would discharge by gravity into rail or road vehicles - for ultimate use as building / road stone.

Anything to big to go through the sieve is discharged to middle of picture 12.jpg to holding bins. This material would then be put through the rod mill again.

It seems the whole lot was probably for precious material extraction - tin (maybe silver / gold). 44.jpg shows a small crusher and manual feed table with a downcoming chute that doesn't seem to quite meet up - this chute probably coming from the fine end of the rotating sieve. This wee crusher would be producing the valuable ore. I would have expected some sort of washing table for separation of the ore, but maybe that is in the separate shed?

Reject from the wee crusher (which I see has already been restored) is taken by bucket lift back to the top of sieve area to go round again.

It is a bit tricky to see just what goes where from the photos, but it will be a beautiful model when done up. I would suggest some research on Cornish tin extraction or possibly Welsh silver / gold extraction would be fruitful.

Best of luck with your project.

Martin

Hi Duncan,

The first material in my collection were responses by Martin Evans and D.E. Lawrence to an article by E.C. Martin in the M.E. for March 19, 1971. The article by Evans gives some background to the Keiller tube factor; it seems this was derived by C.M. Keiller from correlation of the proportions of full size locomotive boilers. In addition, all the boilers "correlated" seemed to be express or mixed traffic standard gauge examples. (Choosing the data to suit the theory perhaps?) Keiller recommended a factor in the range 55 - 70, which many these days seem to think is a bit high - which rather ties in with Julain's comment "I have always used generous tube diameters via length for both ordinary flues and superheater flues."

Keiller quoted work by Dr. Wagner of the German State Railways. Dr. Wagner had concluded that for maximum heat transfer, the gas flow area to heat transfer area should be around 0.0025, equivalent to L = 100 D - which has been called into question at the recent ASTT conference! Tubes of that length would certainly give good efficiency of the BOILER, but not necessarily of the whole loco.

If you look at the Ewins boiler factor

Eb = Grate Area in square inches x Tube Length in inches

Number of tubes x (tube diameter in inches)²

you will see it contains the Keiller factor. Ewins did a write up in EIM in the '80s but I don't have the reference by me just now.

As you know, I happen to think that with the computing power we all have these days, we can do a lot better than these formulae.

I am currently producing some worked examples starting with a "Speedy" boiler, which shows performance will be remarkably insensitive to changes in flue size - provided you keep roughly the same flow area. Things are a little more sensitive to flow area, but there is still plenty of leeway in practice.

Hope that helps a bit Duncan.

Martin

Here is a sketch of how I worked a caged governor valve into my 4" Burrell SCC model. I don't have my original drawings, so have had to re-work this from scraps and memory. I can e-mail a .dxf file which will be easier to read - p.m. me with current e-mail address. The 3/8" cross drillings can have the ends plugged, but the valve chest cover gasket will do the job anyway.

I did find a sketch showing I thought about a valve with 45 deg. seats and slightly different seat diameters - but I obviously copped out of trying to make it seal! However, see my comments in an earlier post about this design not sealing sufficiently well either!

I hope it is reasonably clear.

Martin

Hi Andrew,

I agree with your proposal to analyse the leaf springs as 4 back to back cantilevers. To give you some more design flexibility, some of the original Pickerings had laminated leaves - I have seen up to 3. The earlier photo in this thread just about shows it. (I think!)

On the theory side, I think there are 2 cases to consider - steady state and time dependant. My description dealt with steady state - it is quite possible to end up with an inherently unstable governor if the change in Wr2 on the balls exceeds the change in force on the spring(s). Hence the attention needed to spring rate. Note no friction is considered in this analysis, but friction will make the situation worse.

It is also possible to get time dependant instability due to rapid changes in load, or periodic fluctuations in load coinciding with the natural response frequency of the governor system. I would suggest this is likely to be less of a problem in a steam engine model, where things happen relatively slowly. Remember the originals were built to cope with sawbenches and threshing machines - and quite a lot of skill in feeding both was required.

I also think there is an inherent problem with the sliding plug valve on the Filby design. It needs to move quite a lot to control, whereas the twin seat balanced valve is "fully open" at 1/4 of the seat diameter - I make that about 18% of the sliding plug travel (1/root 2 divided by 4) for a given passage. Having said that, unless the boiler pressure is way down, I very rarely have to open the regulator more than 1/4 travel, so it might be possible.

Have you made the cylinder blocks? If not, I will try and dig out what I did by way of wangling a caged valve into the design.

Best Wishes,

Martin

Hello all,

I have only just come across this post, but hope I can shed a bit of light.

First, the theory, Imagine a graph of governor opening up the left and speed across to the right. To govern you must have a curve that falls from left to right. To get isochronous governing, you need a curve that is a vertical line at the desired speed. In practice the best we ever get is a very steep slope - even on electricity generation work. As Andrew has derived in his post of 15/7 you need to get the springs and masses right, otherwise you can get instability (hunting), when the curves described above on the opening / speed graph become a Z shape.

In practical terms, for a given mass of balls (bit like this post) you need the correct spring RATE. Changing pre load will change the set speed, but does nothing about stability or instability. You will also appreciate that to get some degree of governing with a modest speed variation is in theory achievable, but to get good governing you are trying to create that very steep curve, while avoiding creating a Z curve.

Everything that has been said about increasing forces by increasing rotational speed, and ball mass is correct and will give more actuating force.

The Filby design is dire, in that the governor is expected to move a cylindrical plug with 160 psi pushing it to one side - think if the stiction! On the 4" Burrell SCC, I managed to work in a scheme of drillings to achieve what Duncan has sketched above. I then very carefully made a wee bronze cage loctited into the block and a stainless bobbin,. After many years of further work, I was able to see if it would restrict speed. Under "no load", it didn't.

After 10 years of running the model, the governor drive pulley always has a load of oil on it - so I concluded that trying to drive a governor with a flat leather belt was probably a non starter.

Taking those two factors into account, my enthusiasm for working governors rather died. However, I have the world's only model of a Burrell Patent Dustproof governor - but without the internals completed. I then decided to build a 7" scale steam lorry, but that is another story.............

If you can do it, Andrew, I will be the first to applaud, but please don't get trapped down that avenue - I want to see your two engines in steam - governor or not!

All the Best,

Martin

Thanks for that John - ultra quick on the reply too!

It's no surprise that there seem to be quite a few alternative superheater layouts for Simplex then!

Many thanks,

Martin

I am doing calculations on several Loco designs to determine the amount of superheat. I know the Simplex has a single superheater flue 1.125" OD, but I don't know what the drawings show to go in it. I guess it would take 4 passes of superheater tube? What diameter? Maybe a Schmidt type arrangement? Or 2 parallel out and back pipes - one for each cylinder perhaps? Is a radiant arrangement intended?

Description and major dimensions would be greatly appreciated.

Thanks in advance,

Martin

Hello

I am currently analysing past IMLEC results to try and improve the thermal design methods for small boilers. Please can anyone help with the following dimensions of the 5" gauge “Brittania” design:

Cyliner bore

Cylinder stroke

Wheel diameter

Grate length

Grate width

Firebox height

Firehole diameter

Smoketube diameter and number

Superheater flue diameter and number

Length of tubes

Working pressure psi

Safety valve bore

Many thanks in advance

Martin

Hello

I am currently analysing past IMLEC results to try and improve the thermal design methods for small boilers. Please can anyone help with the following dimensions of the LBSC “Speedy” design:

Cyliner bore

Cylinder stroke

Wheel diameter

Grate length

Grate width

Firebox height

Firehole diameter

Smoketube diameter and number

Superheater flue diameter and number

Length of tubes

Working pressure psi

Safety valve bore

Many thanks in advance

Martin