Bengs models 'Sophie'

I have a lifelong inability to translate tech drawings/plans to the solid ... not ideal for model engineering!!

Presently dawdling through the Bengs beam engine Sophie and, having completed the beam support pillar, the base plate is next. It appears to be secured to the pillar from underneath by a 4mm countersunk screw and the plate secured to the wooden plinth by 4 countersunk screws. These latter appear on the plan to be upside down!! i.e. the countersink is between the plate and the wood, rather than on the top surface. How likely is a commercial company to make that sort of error? I am intending to go with commonsense rather than drawings unless somebody can advise otherwise!

rgds

Bill

Post a photo of that bit of the plans.

Bill, is it possible to include the small portion of the drawing containing this detail in a post? I wondered if the upside down screws were to hide the countersink and allow washers and nuts to be the visible means of holding things down but I may have got it wrong!

Brian

There are photos on the Bengs web site of finished engine which might clarify.

Edited By David Jupp on 13/09/2018 13:23:52

Apologies Jason et al - should have engaged brain re. pics. See below

As you will note, the 'instructions' have lost a little in translation ... almost a touch of the 'Stanley Unwins'!

The part 42 drawing shows the 4 corner holes as having the countersink facing upwards but I assume they are to enable the pillar to be fastened to the support block (??) so should face downwards - yes??

rgds

Bill

The 4 corner holes are shown correctly with the CSH in the top face which has the decorative chamfer all round and the central one should be the other way round so the larger screw comes up from below. The side elevation below the plan view is showing the part upside down.

I think I would be tempted to use studs and nuts for the corner fixings rather than CSK screws.

I think its (a) drawn upside down and (b) the centre hole should be countersunk from the other side.

Looking at the GA the plate should be mounted chamfer up, and screwed to the base with the four screws (just visible in the GA top view) so the centre hole attaches the plate to the column.

Neil

I can't imagine that a full-size beam engine's centre column baseplate would be held down with huge slotted countersunk screws. So I'd be with Jason for studs and nuts on that.

The drawing has the usual bizarre orientation of a first-angle projection, with the additional error that the centre screw countersink is indeed on the wrong side. So I'd be with Neil on that.

Interesting and revealing that Jerry can mess up just as much as anybody else. The translation is so bad that it suggests the original German wasn't especially lucid.

Jason, Neil, Mick, thank you. That all makes sense and I'll go with the hold-down studs as well. Given the quality of the 'plans' and instructions, I may well return for further (much needed) assistance!

rgds

Bill

"How likely is a commercial company to make that sort of error? "

Answer: Very often with drawings for model engines because they are drawn by apprentices or draftmen with little experience to cut down on cost. Construction details are also simplified to make it easier to build. A set of drawings for a model engines are inexpensive, a couple of hundred dollars/pounds at most. If they were commercially drawn professional drawings they would cost thousands. You get what you pay for and all model drawings should be checked prior to manufacture. Most contain mistakes.

Paul.

Yes. Every engineering drawing office I worked in and around had a full-time specialist checker whose job was to trap rookie errors of the sort Jack's found.

Nevertheless stuff gets through - I can remember a cross hole (drawn as blind and needing to be so) dimensioned as being counterbored and tapped 1 1/2" deep in a barstock component of 1 1/2" diameter.

I can also remember drawing up a milling fixture myself which got past the checker, but which the toolmaker came in to the DO to point out was impossible to assemble! Fortunately he was a decent bloke and pretty capable - he already had a proposed solution.

Sophie is quite a nice model to make, just a little on the small side, lots of fiddly bits. never spotted the mistake you have highlighted, but common sense can come in handy sometimes. The cylinder assembly is perhaps the most difficult part, but is essential to get right for the engine to run.

I have only run mine on air and it will run quite slowly as a beem engie should.

It currently has pride of place on my sideboard.

A note for possible purchasers, this model kit only has German instructions (unless something has changed!)

My German to English translation wasn't too good either but managed toi get the job done as the drawings are perfectly adequate.

enjoy the build, let us know when you have it running.

there are photos in my album

Edited By Howi on 14/09/2018 09:16:40

"Very often with drawings for model engines because they are drawn by apprentices or draftmen with little experience"

It's a CAD drawing so doesn't mean it had a "Draughtsman" driving it. The wonders of compukers and drawing packages.

Regards Ian.

Thank you, Howi, that looks absolutely super! If mine turns out half as well, I shall be happy. Given your caveat on the cylinder, any tips?

rgds

Bill

the cylinder needs a part between the cylinder and valve box to be soldered to the cylinder. this need to be square to the cylinder mounting holes otherwise the alignment for the valve operating bits will be out of kilter and will bind. (guess how I know?)

i used a seperate piece of wood to mount everything on to get it running before transfering these holes to the piece of wood in the kit, surprisingly enough the hole layout for the wood mounting block turned out to be accurate. I thought I might need to make allowances for my bad engineering skills!!!!

another thing I did was to replace some of the 2mm brass nuts with acorn nuts, especially on the beam components as they look better, not easy to find, but they are out there.

Howi et al - plodding on with Sophie and need to attach the parts 43 (2off) to part 38, which has preformed 3mm rebates for the purpose. I am assuming that the options are soldering or super glue. My soldering talent is pretty awful, so I'm inclined to loctite or similar. The 43s provide support for part of the beam motion. Would Loctite be suitable? If soldering has to be the method, would paillons of cored electrical solder be suitable or what is recommended? Material for both is brass.

rgds

Bill

I think soft electrical solder would do on a small engine like this.If you have separate flux apply some first.

I would be tempted to make use of the M4 clearance hole for a screw with large washer/plate and a nut to clamp the two arms onto the column top and also put a spacer (24mm? ) at the far end of the arms to keep things parallel and slip a 2mm drill through the holes too.

Thank you Jason. The clamp and spacer idea is splendid .. and just what differentiates 'proper' engineers from the likes of yours truly - so obvious when pointed out but needs a 'tuned' thinking process!

rgds

Bill

Another cry for help, please!

The beam on Sophie is annotated with measurements I don't understandviz. "3H7 and 4H7". Could someone point out what is , probably, obvious?

rgds

Bill

The Germans like to put tollerances on their drawings. The H7 part is the tollerance the holes should be made to which for our purposes means that these holes should be reamed rather than other holes that just show the diameter which can simply be drilled.

So 3H7 means a hole reamed to 3mm nominal with a H7 reamer and 4H7 means a hole reamed with a H7 reamer.

On small holes like this drill say 0.2mm under nominal and then ream.