Member postings for julian atkins

Hi Greg,

An interesting design of handpump.

I think you just had bad luck with the pump cylinder.

The cylinder is a bit on the thin side which probably hasnt helped.

Note that after silver soldering, brass will be annealed, and not the best material to use.

A gunmetal casting is available. If you dont want a double acting pump you can use the casting provided for your County Carlow loco.

Cheers,

Julian

A few points.

I know nothing about electric motors.

All my steam raising electric blowers use ex WD 24V motors. Most clubs have 12V and 24V supply on the steaming bays. If they have air lines via a compressor I much prefer this with a tube dropped down the chimney that has a 'U' bend on the bottom.

The car Smiths type heater fan doesnt work well on 12V but ok on 24V. However the fan itself is usually plastic.

The temperature of exhaust gases via the smokebox will eventually be well above what the fan can cope with. And the ex auto type motor will also get very hot.

I would much prefer clubs to have air lines instead of having to rely on electric motors on top of the blower vanes.

I havent seen the article yet in ME.

Cheers,

Julian

Hi Rob,

Many of us are familiar with Simplex and Super Simplex.

What we dont know from your posts or album is how your's compares.

What sort of repairs are required?

Cheers,

Julian

Do not peen over the lip of the firebox hole ring. It negates the 2 to 4 thou clearance required for silver solder penetration.

Cheers,

Julian

Hi pgk pgk,

If the firehole ring is turned accurately with registers/rebates and then squashed to shape this would usually be enough to keep the distances of the backplate ok on what is a relatively small boiler. Try a few dry runs first. I would silver solder the bushes to the backhead with J-M silverfo 24 first which saves a lot of angst and worry on the final stage, as there is otherwise too much to worry about, what with the rear foundation section as well.

If you can get some JM easyflo 2 for the final backhead stage you will not regret this. No longer 'sold' but there are a lot of fellow forum members who might have a stock of it to help you out. Unfortunately I have precious little left, and cannot help you out.

The silver soldering on the smokebox tubeplate looks very good. This is the last bit I do before the backhead.

Cheers,

Julian

Edited By julian atkins on 07/12/2016 23:53:28

Hi Mike,

Perhaps first to consider a rolling road test bed, as a 6 ft length of track wont be of much use.

If you want to make up a decent test track advertise on here for some local ali rail.

Or just join your local club?

Cheers,

Julian

Hi Greg,

I use 1/2" x 26 tpi ME thread for boiler bushes and fittings of this size. I go down to 32 tpi ME thread for 3/8" and below till I get to 1/4" when I use 40 tpi and for smaller sizes.

I have 32 and 40 tpi dies and taps for 1/2", but are not used on boiler work.

Cheers,

Julian

Hi Ryan,

You have approached the problem from the wrong way.

You need to work out the correct valve events in fullgear, then work back from this.

I always make the reverser to suit the gear.

You need to be avoid overrun of the valves in fullgear.

You really ought to run the Tich valve gear on a computer simulator for valve gears, though I am not aware of any particular errors in LBSC's gear as designed. Some fine tuning has been done to LBSC's Juliet, but I am not aware this has been done for Tich.

Cheers,

Julian

Hi BK,

It is a difficult to get these bits to fit. The major problem is lack of undercut at the end of the threaded fitting, or lack of counterbore on the bushes. Also remove all burrs. I always aim for a metal to metal mating, with, on screwed in fittings a smear of red hermatite type sealant (no longer obtainable, but there are other substitutes).

I would never use Loctite on boiler fittings. Think what you may have to do to remove them for maintenance.

Cheers,

Julian

Hi Michael,

FSD = Frederick Samuel Dinnis, born 1st October 1903, died 18th July 1989.

The address in Ward Avenue Cowes was a very nice detached house though bombed out in WW2. That address will be be very well known to older model engineers of the loco fraternity.

Cheers,

Julian

Here are top row 3 FSD (Freddie Dinnis) miniature gauges of 3/4" dia. The first is an early example with curved glass and dates from circa 1970.

Below 3 knackered old gauges with corroded brass bourdon tubes.

Cheers,

Julian

I have to disagree.

Both Roy Amesbury and Freddie Dinnis (in Freddie's case commercially) made their own pressure gauges of scale size for 3.5"g and 5"g locos etc and all were perfectly accurate. Freddie's were so accurate they were used by Rolls Royce.

You can read the accuracy very well same as you use your eyesight to read a vernier caliper.

Roy used sifbronze rod drilled and reamed to fit onto a mandrel via loctite to turn the finished size for the bourdon tube before flattening and curving. I have used the same method. Roy described making his gauges on a number of occasions in ME.

Alan Dinnis has published a book on Freddie's life, his father, which includes a chapter on his gauges made when in 'retirement'.

I remember being shown how most of the parts were made in the mid 1980s by Freddie including how the phos bronze bourdon tube was drawn. I have a number of lengths if anyone wants to have a go at making their own.

Any purchaser of a gauge from Freddie was often subject to a trial of the calibrated gauge on the dead weight tester before money was handed over. Some of mine are 40 years old and all yet are as clear in reading and accuracy as when first made in Cowes Isle of Wight.

I bought a 1" dia vacuum gauge from Reeves in 1990. The vacuum gauges require thinner bourdon tubes. (Freddie made these as well). The Reeves vacuum gauge with its brass bourdon tube lasted but 5 years before the bourdon tube corroded. I have a box full of old commercial miniature gauges with brass corroded bourdon tubes from the days of Bassett Lowke and Bonds O' Euston Road.

Cheers,

Julian

Here is the master. The late Freddie Dinnis with his dead weight tester with one of his miniature gauges being tested (can be seen below his right shoulder).

All Freddie's gauges had proper drawn phos bronze tube, and each gauge was individually calibrated. They are now much sought after.

All the current commercial small scale gauges use brass bourdon tube which due to it's thinness is apt to corrode over time. None are individually calibrated, relying on printed discs.

As all my locos have FSD gauges I cannot comment on the current commercial examples except for the above corrosion comment and lack of calibration. However I would add that the 'red line' is merely to highlight the working pressure of the boiler. If a commercial pressure gauge was not accurate, it would fail a boiler test regardless of the red line.

Cheers.

Julian

Other future model engineering topics for a model engineering website..

How to lay and fit a carpet,

and how to tile a bathroom.

Cheers,

Julian

Hi Bruno,

I overhauled and ran a lot a Princess Marina many years ago. An excellent loco. I dont think the change to piston valves is required but if you insist on this change you need to study carefully the Doris design and ideally work out on a computer valve gear simulator the changes required. The obvious change is in the combination link.

Cheers,

Julian

Hi pgk pgk,

That is a much better pic, and I would pass it, especially as my last boiler has webbed feet on the crownstays to the inner wrapper. I also always add large holes through the crown stays to help circulation.

My usual practice is to silver solder the inner firebox wrapper to the tubeplate, then silver solder the tubes in position, then do the crownstays to inner wrapper, then silver solder the firebox doorplate to the rear of the inner wrapper.

You are going to have fun and games trying to silver solder the tubes applying heat from within the box with the firebox doorplate silver soldered in position. The flame will probably go out continuously, and you risk disturbing all the joints already done.

L C Mason didnt have much experience of building miniature boilers, and the usual practice used by LBSC, Don Young, and Martin Evans for loco boilers seems to have been lost on Mason.

Cheers,

Julian

Edited By julian atkins on 21/11/2016 23:48:03

Hi pgk pgk,

It usually takes me 2 attempts to get the crown stays silver soldered to the inner firebox wrapper, in each case without the rear inner firebox flanged plate attached.

In your above pics you appear to have attempted this with the rear inner flanged firebox plate in position and silver soldered to the inner wrapper - though this isnt clear. If so, it would not be the recommended proceedure. The pic is not clear but there appears to a want of heat and blobbing of silver solder which hasnt run into the joint.

However this is only a guess from the blurred pic.

On my my first boiler I used 1.5mm dia rings on the water side ends of the tubes abutting the firebox tubeplate. Excessive, but went ok. (I had nothing smaller in dia of silver solder at the time).

Cheers,

Julian

Hi Brian,

I would not bother with tinning the surfaces.

Just rivet it up tight metal to metal then do what most of us do for loco side tanks and tenders...

Get some Bakers Fluid flux (easiest these days to get off ebay),

and some old fashioned plumbers stick solder (I have a large box of it if you want any).

Heat up gently, spoon in a few generous large spoonfools of Bakers Fuild and swish around. I use an old brush though you can make a copper wire brush quite easily. Then add the stick solder. Add more Bakers Fluid as required. The soft solder will quickly wizz though all the joints and seal perfectly in less time it took me to type this.

Wash and scrub the joints thoroughly afterwards with a toothbrush and hot soapy water. You may need to do this a few times a few weeks apart.

Cheers,

Julian

The problem with fabrication if silver soldering the parts together is that the brass will be soft. It can be age hardened. I dont know of a quicker process. I remember LBSC stating even phos bronze/gunmetal should not be silver soldered for cylinder and valve parts as it significantly affects the wearing properties. Whether this is correct or not I dont know myself.

Generally one should avoid brass in cylinder parts as it wears badly anyway compared to gunmetal castings or bronze.

If you are building a 3.5"g loco it would be a shame to spoil it by not using the correct materials for the job.

Cheers,

Julian

Hi Ryan,

I have some 4mm BMS angle that is very accurate. If you can get same, it saves one silver soldering joint. Or else mill dead square some black angle iron.

As for the other...

I would bolt onto the motion plate the outer trunnion for the expansion link - after all the other inner one is also bolted on!

Cheers,

Julian