Member postings for Chris Gunn

Sam, I would not use steel on steel for your bearings, I was taught never to use similar materials for this type of assembly. You will inevitably finish up with water in the bearings one way or another. Neither would I use brass if you intend to run it. I am not familiar with the design but looking at the video it is not a big engine, so using commercial bronze bushes in a housing is the most economical way to go. What size do you need? you may find someone on here has just what you need in their scrap bin and would be happy to help a beginner.

Chris Gunn

Insulation and a dehumidifier works for me, but if it is damp keep the door closed or it will try and dehumidify the world. When going away for a few weeks I spray the machine beds and ways with maintenance spray or WD40.

Chris Gunn

John, the steel tubes tend to rust through on miniature engines in about 10 years, this is due to them being exposed to the most heat, and yes most of us use boiler treatment. When I changed my tubes a few years ago they were pitted and wasted away to nothing in places, and I have seen several identical examples since then. However as far as could be seen through the manhole the much thicker boiler shell was in really good condition.

Chris Gunn

Mark, I have some 16G, which equates to 1.5mm if that is any good to you.

Chris Gunn

What an interesting thread, here is my twopennorth, Like Bill I was brought up on manual machinery, and turned the handles for myself, and continue to do so now to create my miniatures. I do use DRO's now to maintain accuracy as the ability to see as good as I did at 21 diminishes slowly. The next generation will surely use the machine tools they are familiar with, probably CNC controlled equipment, provided they can afford them. At the moment they would have to do their own programming, so would be using a different skill set than us old boys are familiar with. Surely that does not diminish the results of their endeavours. To my mind we should be pleased that there is another generation following who will continue the hobby. I wonder if in the future the suppliers will offer a set of machine code to produce all the parts to make a loco or traction engine instead of the drawings? I am more than happy to take advantage of what modern technology can offer, for example I would rather buy laser cut spokes for my next traction engine than carve them out myself, as I can make much better use of the time available. I know I could make them, but choose not too. I feel the skill in building the wheels using the spokes is more indicative of what I can do than tedious repetition. I know some folk like to do everything from scratch, from measuring up a prototype to pattern making to making the parts, and good luck to them. However this is very time consuming, and I do not have the time needed to go through this, so I took advantage of the parts available to shortcut some of this and as a result I have built 2 traction engines and have had years of fun running them as well.

Chris Gunn

I served my time at a manufacturer of high speed rotary printing machines where grinding was the norm to finish large precision rollers plus many surface ground parts, and coolant was used for everything. Not only did this keep the dust down and allowed good metal removal rates but also ensured the finish was good with no burning on the surface. I remember that if the coolant was off on the J&S, one could get a brown scorch mark on the surface taking a thou cut, so coolant was the norm.

Chris Gunn

I am surprised there is no coolant tank, I remember them having quite a big unit with a settling tank to separate the grinding dust. I am not sure what work you intend to do, but I would have thought coolant is essential to get the best out of the machine. I ran one for 6 months during my apprentiship on production work and coolant was always on.

Chris Gunn

I guess you may need to make provision for the coolant tank motor as well?

Chris Gunn

I made hundreds of gear blanks when an apprentice, and soft jaws are the best method, if the standard hardened chuck jaws are not true then a split bush may not correct the error unless one is very careful.

Chris Gunn

Jason, as said earlier I was inspired to make a start and had a rummage around and found 2 round cast test pieces about 5" diameter I scrounged from a foundry years ago, and parted off a slice and then thought I would do 1 for each of my grandkids, 4 in all, so parted off 3 more slices. I have made everything except the con rod and piston and the flywheels since the beginning of May for 4 engines all from the come in handy box. I have just bought the Perseus flywheels from Reeves, I had to get 10 to get a discount, so I have 2 spare Perseus flywheels. If anyone wants these PM me, first come first served. I will take some pics at a later date.

Chris Gunn

I did my apprentiship at a high precision printing press manufacturer, and we worked to fine tolerances, on machinery that could deliver them, and with the appropriate measuring equipment and gauges. This has remained with me and I still try and work to such tolerances even though my equipment struggles to match what we had back in the day. Now I build working steam engines I have found that it is a disadvantage to be too precise on some jobs as expansion and a dirty environment means that precision joints can seize up. One needs to leave space in the joint for soot to fall through. I think the key to success is knowing when precision is needed and when it isn't.

Chris Gunn

I think you are making the job more complicated than it need be by drilling the crankshaft hole from both sides, the chances are it will not line up so why take the risk? See my earlier post about the drilling procedure I would adopt.

Chris Gunn

Fizzy, I remember reading somewhere "If using nitrile balls go one size bigger than you would for a steel ball", so your reaction was probably correct.

Chris Gunn

Jason, I will take a few pictures of the Undertype in due course, as I am still working on it. I was lucky enough to win an auction for the drawings and castings on a well known auction site.

The cylinders and crankshaft were already machined to a very high standard indeed, so as I have not made it all maybe it is not suitable for publication. It is a nice model I always wanted to make back when I was a lot younger but could not afford the castings. Then it was discontinued so I thought I had missed the boat. The engine goes back to a design by Henry Greenly, and was revisited by H A Taylor who did a series in the Model Engineer starting in March 1971. The design was then taken up by Stuart Turner who produced the castings, but I am not sure when the engine was dropped from the range. It is a change from the 4CD for sure, while I decide whether to make another traction engine.

Chris Gunn

Jason, thanks for the series, I have downloaded the drawings and intend to make one when I have finished my Stuart Turner Undertype.

Chris Gunn

Rod, I made a similar engine for one of my model boating friends, and I would proceed as follows. The base is the natural datum for this engine, so I would set the casting up in the vice with the base uppermost, and skim the base. While the base is uppermost I would drill the mounting holes. Then I would make a sacrificial base plate out of a scrap of anything handy, making sure the sides are square with each other and overhang the casting base by 1/2" all round, then mount the casting square on the base, then use the sacrificial base plate to hold the casting and as a setting aid as you proceed. As the mounting holes are small, use additional supports and clamps to take the machining loads. I would not bother trying to drill the shaft hole from both sides, just make sure the face of the boss is flat, skim first, and start with a small centre drill just to dimple the face, the drill will snatch in bronze if you go any deeper, then use a new quality drill for the hole, this should not wander over such a short distance.

Chris Gunn

Sam, I have machine reamed thousands of gear blanks made in EN24 with adjustable reamers, but these are of the David brown 2 bladed type, I guess you used the multi-bladed type which are not suitable as stated.

I would re-bore and make the piston to suit as suggested above.

Chris Gunn

Ron, I just scrounged a U/S fan from the guy that serviced our heating, my CH boiler has a fan exhaust as many do, and these fail after 7or 8 years, this is the third new one on my boiler. The fan motor was gone but the fan was OK. this is a steel fan in a steel housing so can take the heat. It is simple to remove the old motor and fit a 12/24v motor of your choice. You will need a adaptor, also easy to make. I suggest you make friends with a gas service engineer or go on the scrounge round the local service place.

Chris Gunn

I have had gunmetal castings with a distinct greyish tinge, but easy to tell when you have them in your hand that they are in fact gunmetal. However maybe not so obvious from a poor quality picture in a magazine.

Chris Gunn (no relation)

Jim, I have a spin indexer and it is very useful, however mine is a Marlco which is heavy and really rigid when locked. I bought mine second hand at one of the shows for about £60, some have chucks fitted like mine with inside and outside jaws, some have collets fitted. They appear in the usual places occasionally.

Chris Gunn