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7 1/4 Tich drawing Errors

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Peter Brown 127/02/2020 16:53:37
9 forum posts

I don’t know how anyone has managed to build a 7 1/4 Tich from the Kennion drawings. If you build the frames and axles to the drawing you end up with 3/16 inch end float on the axles, also the motion work fails to line up correctly the cross heads foul on the coupling rods on the front wheels also the cross heads fail to line up with the coupling rods. My drawings are old so I contacted GLRKennions to see if the drawings had been updated only to be told no, not only that but they know about the errors but have done nothing to correct them. Surely to sell an item that s not fit for purpose is wrong, if I had machined expensive castings to an incorrect drawing would I have any comeback? I have now spent several hours redrawing the motion to find a solution and am dismantling the frames to correct the end float whilst maintaining the correct gauge. Has anyone else come across this problem and if so what is their solution?

Dave Halford27/02/2020 17:48:52
616 forum posts
5 photos

Guidelines smiley

Nick Clarke 327/02/2020 21:33:48
573 forum posts
14 photos

Look at the boiler drawing - the hollow blower stay screws backwards into the blackhead and simultaneously forwards into the smokebox tubeplate. An interesting job to install!

Also while not an issue on a track with no points, but the spring pins foul pointwork if not shortnened.

Peter Brown 127/02/2020 21:55:10
9 forum posts

You are right, wheel radius 2 1/16th protrusion of spring pin 2 1/8th Also there is no drawing for the saddle. I have a professional made boiler so I won’t need to worry about the hollow stay.

I have completed a Rob Roy but that had drawing issues as well, no wonder there are so many part built locos on eBay it’s enough to make you want to give up and try something different.

Richard Clark27/02/2020 22:57:55
3 forum posts

It is well known in the Model Engineering world that many drawings from various different sources contain errors, and I know that this is much discussed at clubs and on forums such as this.

In the eight years that I have been running Kennions I have discovered that Model Engineers are some of the cleverest, intuitive and inventive people, and very often will solve a problem with drawings; the resulting satisfaction calming their initial frustration, and in no time at all they move on and the problem they had, the exact detail of it, and how they solved it becomes a distant memory only to be re discovered by the next person to come along.

May I just say, as a supplier to the industry, and I speak as someone who has never built a steam locomotive, how difficult it is to persuade customers to advise us in detail of any errors that they have found so that they can be corrected.

Of course we would not wish to sell drawings containing errors if we could correct them and we will endeavour to find someone to take a look at the Tich 7.1/4" for us.
Richard Clark

GLR Kennions Ltd

Peter Brown 128/02/2020 09:49:17
9 forum posts

What has really annoyed me with this is that there are fundamental design errors not just the odd drawing error. On sheet 4 of the drawings for the valve gear if you actually draw in the missing front wheel and complete the coupling and connecting rods it is clear that the crosshead will foul on the coupling Rod and not align with the connecting rod. Similarly on the drawing for the frames and wheels if you draw the outline of the wheel over the horn block and spring assembly it becomes clear that the spring rods extend below rail head. Yes we are an inventive lot and having invested a considerable amount of money in this I will find a way round it and will try to document my solutions as I go.

Phil H128/02/2020 11:43:01
233 forum posts
26 photos


I for one would really appreciate some clear pictures of your problems because I have considered building something like a large Tich some time in the future. It might also help Kennions and others builders.

Phil H

Nick Clarke 328/02/2020 12:13:29
573 forum posts
14 photos

It would be wrong to pick on just the 7 1/4" Tich for errors - many many designs have drawing and design errors, often because they were drawn and not built first I suspect. Have a look at the MECH site to see many posts about many other designs.

As for Big Tich - a 7 1/4" loco that will fit in the back of the car, pull several people, can be driven on a ground level track and not too expensive to build - What is there not to like?, even with errors but no more so than many other designs??

I hope Richard is able to update the drawings - but I suspect proving corrections are accurate and answering any copyright questions may make it a difficult task - however I personally want to congratulate him on standing up for his customers and saying he is going to try to do so. That is a rare, if not unique standpoint to take in my (admittedly limited) experience.

Thank you.

SillyOldDuffer28/02/2020 13:06:58
5369 forum posts
1090 photos

As a fan of old Model Engineer magazine, I can confirm readers have complained about errors in plans supplied with kits, articles, and books since Percival Marshall was a smooth cheeked lad. Finding errors seems to be part of the 'fun'.

Never likely to build anything as complicated as a Tich myself, but even for considerably simpler objects I like to more or less formally redraw plans to make sure I've understood them. Redrawing is a very good way of detecting mistakes and finding missing dimensions. Usually redrawing is no more than a back of an envelope sanity check, but I often go to the trouble of doing a working 2D drawing with projections in QCAD, or even build the object in 3D with FreeCAD. Fusion360 is my go to tool for checking dynamic aspects like joints, alignment, movement and interference, but I've also modelled moving parts in Meccano or Lolly Sticks and Cardboard.

I recommend Stewart Hart's Pottymill as a beginners first engine because the plans have no significant errors. My construction skills and ability to read plans improved enormously after building this relatively simple engine, and I now find it easier to eyeball mistooks in plans. I still check plans carefully though - it's a variant of 'measure twice, cut once'.


Peter Brown 129/02/2020 10:25:54
9 forum posts

Yes I know many designs contain errors and some are better documented than others, Big Tich just happens to be the project at the moment but having a set of drawings which cost £50 I really don’t expect to the spend hours redrawing them I would rather be out in the workshop machining.

If I can get permission I will try to put together an article for the Model Engineer on the problems and my solutions and suggestions to produce a working version of what I hope will be a nice little “big” engine and encourage others to have a go building one.

Richard Clark29/02/2020 10:42:53
3 forum posts

We now have someone willing to look at this with a view to us being able to issue revised drawings.

This may result in the need for adjustments to some of the castings and if necessary we will adjust the patterns to take account of this.

Richard Clark

GLR Kennions Ltd

Nick Clarke 329/02/2020 11:58:28
573 forum posts
14 photos
Posted by Richard Clark on 29/02/2020 10:42:53:

This may result in the need for adjustments to some of the castings and if necessary we will adjust the patterns to take account of this.

Richard Clark

GLR Kennions Ltd

If you feel the need to adjust the patterns for the cylinder block at present it is uncored - it would save metal, time and a deep drilling operation in gunmetal if these were cored out.

I don't expect the additional foundry costs would make them much cheaper to produce and it is too late for me as I already have a couple under the bench waiting to be machined, but only a suggestion.

Edited By Nick Clarke 3 on 29/02/2020 11:59:19

Peter Brown 129/02/2020 12:18:23
9 forum posts

That’s great Richard if they want to contact me I can give them some of my ideas. At the moment I am spacing the frames 3/16inch further apart to get rid of the axle float and then taking a 5 thousand inch skim off the back of the wheels to give a running clearance, by doing this it helps in the alignment of the connecting rod to the crosshead which I think can now be achieved by a slight modification to the big end bushing it also reduces the overlap of the crosshead and coupling rod but does not provide enough for them to clear so I am now considering ways to achieve this, With regard to the spring rods I think I will remove them completely and rearrange the springing as per the 31/2inch version with the springs on top of the axle boxes sitting in pockets which will then also act as oil reservoirs for the axles. At the moment the only casting this would affect is the centre pump stay with needs to be 3/16 longer but in my case I will just add spacers either end.

If I was starting again I would make the frames from 1/4 inch plate which would achieve the same increase in width but would leave the inside measurement at 6 inches but this might require the hornblock castings to be slightly thicker.


Edited By Peter Brown 1 on 29/02/2020 12:31:17

Baz29/02/2020 12:43:59
333 forum posts

Well done to Kennions for trying to solve the drawing errors, if only the other companies were this interested. Every set of drawings I have seen has errors, LBSC, Evans Don Young, to name but a few, ranging from simple errors ie missing holes to Don Young’s almighty cock up of his Marie E design, his mistake was pointed out to him and he did offer a couple of work arounds but not a compete cure. I think we all now realise that most of these designers had a very limited understanding of valve gear, LBSC probably understood it more than the others. I totally agree with the comment about so many unfinished engines on eBay, it is totally disheartening to spend hundreds of hours on something just to find it won’t fit together, I don’t see it as all part of the fun though, as some others do, I feel that as I have paid decent money for the drawings they should either be correct or come with a separate sheet which states that people have reported errors and a list of what they are, we would at least be forewarned.

Kevin Bennett29/02/2020 16:42:38
167 forum posts
28 photos

at last as i struggled with my 5" Tich I have 2 complete sets of drawing both different at one point it was going in the scrap what i did in the end i got the important things working and I have a running chasse the rest will be best fit converted to metric as i feel fit. . I am 3/4 through building the boiler the only thing the drawing need notes on them rather ten getting eye strain looking at it for hours. I must say if a set of drawing was in a cad file in metric I would purchases a set.

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