Portable Engine Model Engineer Article by Tony Webster

Issue 4428

Slide bar drawing

-Plan view gives width over the outside of the bars and bracket as 15/16

-Plan view gives one end of the bars at 13/16" centers and the other end at 11/16" ctrs

-End elevation gives the bracket as 1" wide and the bars project beyond the bracket which would give the outer edge of the bars as 1.125" or there abouts

- and to be picky the oil cup does not show the hole carried through the slidebar

Cylinder saddle.

- is this the actual view of a developed shape of the curved part.

- 1/8" dimension bottom left is wrong should probably be 1/4"

- the two 9/32" dimensions on teh left seem wrong as the hole will break through the edge, 11/32 would be nearer whats right

- No size given for the 4No corner holes to mount to the boiler/dummy wrapper.

- Is it correct that the cylinder does not sit centrally on the curved flange front to back, or should the 3/4" dimension for the position of the 1/4" hole be 15/32" to allow for the 1/32 projection of the cover faces beyond the cylinder.

Its now been some 6 weeks since the first queries were raised any idea of when and if they will be answered???

J

Edited By JasonB on 13/04/2012 15:55:52

Hi There

Cylinder saddle was the wrong drawing. Corrected version in 4429.

regards David

Hi There

The slidebar drawing has been checked and is as supplied apart from the hole which is shown right through.

I will forward the query.

regards David

Piston rod.(Not in 4425) 1/4in dia stepped down to 3/16 and threaded 3/16 x 40 tpi.
To save creating a stress point at such a step, taper at 60 degrees inclusive and
'countersink' the piston with a combination centre drill before drilling tapping size for
3/16 x 40.

Boiler: Height of Backhead 6in.
Height of firebox 4.1/4in. neither is critical.
The wrapper plates are probably overlong and will need trimming to match the flanged plates.
Before fixing the skirt length(see below) check that the lower tubes will fit the lower holes
in the firebox tubeplate, clear of the inside of the barrel.
The important dimension when setting out the tube positions on the firebox tubeplate is that
the top row of tubes should be 11/32in. from the INSIDE of the flange, (or 15/32in. from the
outside of the flange if marking out on the other side of the tubeplate). Do not drill the
7/16in.dia holes until the flanges have been made.
The drawing was redrawn for publication and the tubeplate thickness of 1/8in was not transferred.
The 'skirt' ie firebox below the outer, should be 5/16in..
Foundation ring should be 1/4 square all round but you may be only able to obtain 6mm square.
Use it.
The outer door plate (Backhead / frontplate) and the firebox doorplate should be parallel to
each other and vertical.
The firedoor and the water gauge bush should be on the same horizontal centre line and the
stays should be equally above and below this centre line and maintain the 11/16in vertical
centres. they are offset 1/8in. from the lower ones to place them nearer the centre of the
area alongside the firehole.
Get the blowdown bush as low down as you can, ie. 7/32in. above the foundation ring.

The 1/2in. hexagon for the top water glass connection should not have the 3/16in x 40 tpi hole
drilled and tapped yet. Drill 6BA clear and tap the hole in the boiler 6BA. Fix with a 6BA brass screw.
After the boiler has been silver soldered the screw is drilled out and the outer part tapped 3/16 x 40.
This is for a banjo pipe connection to the pressure gauge

What a complete fiasco this beginners engine has turned out.ME should never have started it.

Dave

I put it off for two years, I wonder why?

regards David

Oh well ***t happens, I suppose it give beginners some idea of the traps that are set to catch even the experienced modeler. I'm one that gets around the problem, don't use drawings, all mistakes are mine (pleanty of those). Ian S C

All well and good but a beginner won't know that these are errors and may get dispondant and give up the hobby when things don't fit together or work. For example if they don't know how an engine is supposed to work they will end up with slidebars that are no where near parallel !! to use the latest issue as an example.

Is this the attitude we should be encouraging??

All these errors are beginning to read like a epistle, there will be modellers out there who don't have access to this forum or even have a computer, who are building the model.

To help those who don't have access to the error information on this site of this particular model, I think the editor should consider publishing free with a issue of Model Engineer a supplement of all the known errors, I fear some beginners may have already thrown their hand in.

Stick.

I think that Model Engineer should print a full set of amended/corrected drawing in the next available issue so that everyone that buy's the magazine is aware of the errors and have something that they can work to now.

It is a shame that there has been so many errors as I was looking at this as a possible project while I was building the Simplex. I have a full set of drawings for the Allchin that I bought on ebay so I will get the constrction book and see if I am able to make that once I have finished the popcorn engine that was run as a series a while ago.

Perhaps the fairest thing would be to print a message saying a list of amendments is being prepared that can either be found here or send an SAE for a print out?

I have to be honest, I check every dimension from the job anyway, as I don't trust my work to be accurate enough

Neil

The best way to do it would be as it was in the past, at the start of the next part of the article any errors or ommisions were dealt with before the build continued. Keeps it upto date and all in one place.

In ideal place to print these would be in the half column that is left blank under each authors photo, that way no extra magazine space is wasted.

Its a shame errors can't be dealt with like one of the other model engineering mags I subscribe to, if any are found a new drawing is produced with CAD and a pdf version sent to the subscribers. A printed version is also published in the next issue. That way you are not held up waiting for revisions and you know of any errors within days of the mag dropping on your door mat.

J

J

An errorata column in Model Engineer may be a good idea, hopefully not in every issue, can't remember, but there may have been one in the past. Jason may have the idea. Ian S C

Hi There

We are working to far ahead to get it in the next issue.

We are about to start 4430 and corrections will be in there.

regards David

Well David this sounds like a complete disaster of a series but I am sure that you are not personally able to build every single model that is published in ME to find errors. Did the author not build as he was working on the drawings and make changes or notes of errors..

Bob

So are you saying the two bars are on 11/16" centres. If so the end elevation is wrong as that has them sticking out beyong the support bracket in which case the 1" dimension is wrong, the 13/16" dimension to the reinforcing web is also wrong and how do teh bars fit each side of teh support which is 9/16" wide, they would need notching around it???

I think a new drawing is needed as there are just too many anomolies on this one to try and describe in writing alone.

Tony Webster has been writing for ME for a good 20 years on traction engine related topics. His It's ashame these drawing errors are detracting from what is a really nice looking model that clearly has inspired a lot of people to have a go. models are always good looking and robust, and he's willing to use a few 'tricks' to get it looking right.

I suspect the problem here is drawings made from the model without complete dis-assembly?

Neil

Just been thinking about what I said above and looking at the photo I linked to on the previous page.

If the 5/16" wide bars are on 11/16" cts that agrees with Davids 3/8" between bars. But the bar support is given as 9/16" wide ( this looks in proporting) so the bars would need to be notched out to fit round it making the bar ends 7/32" wide, this would be why the bolt spacing is increased to 13/16 at this end.

Looking at the photo confirms that the bearing surface of the bar is wider tha the end that we can see.

David can you confirm if the front end of the bars are notched and if so why was it not on teh drawings

Another greek C**k up that has made it hard to follow is that the 15/16" & 5/16" dimensions shown against the end of the plan view actually apply to the side elevation, the 5/16" being the Horiozontal gap between the slide bars and the 15/16" is just about right for the height of the oval cutout in the support post.

Edited By JasonB on 29/04/2012 19:17:28

Further to the above this is the "drawing" as ME click both to enlarge

And based on Davids Measurement, looking at photos and applying a bit of common this is a quick sketch of what I think it should look like

J

Edited By JasonB on 29/04/2012 20:38:37