Engines > Restoration of Model Engines

An absolute beginners journey to restore a Viking 2.5cc Diesel

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I should probably start with a quick intro of myself even though I’m one of the first members here.

Right out of primary school I started at “Århus Tekniske Skole” (Aarhus Technical School) at “Svagstrømsteknisk Værkstedsskole” (~ Electronic Workshop-school) in 1978. This was the first step towards an education for either “Elektronik Tekniker” (Electronic Technician) or “Svagstrøms Ingeniør” (a Master degree in Electronics). This was three semesters from August to June. In each semester we alternated between a week in the electronic workshop and the next in the metal workshop. On metal weeks we had Wednesday doing drawings, how to write to correct types (font) on the drawings by hand, etc. and the other four days working on metal. First semester where how to correctly mark and measure on metal, hand file a straight or curve, use a hacksaw correctly and choose the right blade for it, use a drill press and how to sharpen the drill bits, use a brake on sheet metal and finally how to hard solder.

Second semester where “mastering the lathe” and third semester “mastering the mill”. In all three semesters we had to make tools and professional enclosures to the electronic projects – I still have all those tools and some of them I still use often 

So why do I call this : An absolute beginners journey to restore a Viking 2.5cc Diesel ?
Well I haven’t used any of those skills in the years between and as the Yanks say – Use it or lose it – so I have lost most of it (hopefully not including all my marbles – though I’m brain damaged after a MC accident in 94). I was also born dyslexic – so writing has never been something I liked to do, but ….

It was not my intension to start with the Viking, but one of the more simple worn / damaged model engines I acquired over the last seven years or so, but I came into contact with Luis Petersen, multiple World Champion Team-racer / engine builder and he gave me some of the parts I needed to get my old Viking (1950) running again +  I more or less promised him that this would happen in the not too distant future.

Luis told me that he used grade 10 high tensile bolts, for his cranks and pressed in “lokke nåle” (punch needles) a la : http://power-tools.dk/Resources/Files/pdf%20norm%20snitstans/Posaunen.pdf for the crankpin.

We agreed that the Viking crank is too thin for a pressed needle. I found and ordered 10 M22 bolts from eBay.de at €1 a piece.

For those who wishes to read the story of Danish model engines and the Viking in particular, have a look here :


Here is the engine in question – or more correct how it should look :

Sorry I had intensions of posting the next two instalments now - only to discover that I need a place for the pictures ....  :wallbang:

I do like the look of the little Viking 2.5cc Diesel.

Per I hope you realise I will now have to go and have a look through my model aero engine casting sets for something equally nice  :embarassed:



--- Quote ---I do like the look of the little Viking 2.5cc Diesel.

Per I hope you realise I will now have to go and have a look through my model aero engine casting sets for something equally nice  :embarassed:
--- End quote ---

Well I'm almost sorry for you Jo .... but then again, you might need to do something other than making three times the number of parts for an engine  ;)

First I put the hex end of the bolt in the three jaw chuck and center drilled it so I could use my dead center, only to discover that there was no way that was possible  :rant: . For one, I had placed the Y-axis glass-scale between the “main-sledge” (I have never seen anybody name it here) and the headstock.

I tried to turn the bolt anyway, just to see if the result might be useful anyway – nope – I had to move the glass-scale. That took a few weeks before I had the new parts to do that. Only to discover that it was still not possible, for two reasons. The original tool holder took up too much space and the dead center did the same in the other dimension.

The first problem was solved by Niels Abildgaard, who very kindly lendt me his Tangential tool holder + some tools from Arc Euro Trade, I ordered a mini live center, a half- dead center, some diamond paste for lapping and a few more items.

I haven’t got a picture of the first operation. I removed the thread with a new HSS tool that got blunt from trying to cut 0.3 mm per pass and the bolt wobbled quite a bit afterwards as I could see on the center hole that was not on center anymore.
First picture is the bolt after I have rebuild the glass-scale mounting and have received Niels tool – you can see that I just skimmed the corners of the hex.

Niels tool worked fantastic – I took 1 mm interrupted cuts at more than 30 mm diameter – No worries   Result can be seen I picture two.

First major UPS before I got the half- dead center can be seen on picture three - I forgot to lock the ram of the headstock. I started out fine, then the cut got deeper and deeper and sounded bad !   :facepalm:

Lesson learned : Do not try to figure out why things are going wrong while cutting !!!
HIT the stop button immediately !!!! – this might have prevented the marks on the crank web and almost certainly prevented the embarrassing marks on Niels tool – I now owe him a new one + you have plenty of time to contemplate after the lathe is shut down ….
Oh well – you can only gain experience by making mistakes – first one on the list .

I got my tools from Arc Euro Trade, and in order to try them, I thought ; Why not try to continue with the “scrap part” – after all it might still be a runner, even if it won’t be a pretty one. First picture is the crank turned down to the diameters for the last operations on the shaft side.

I had planned to use my single point tool to make the M5 thread, only to discover that I needed two 80 teeth gears for the box and I have only one  :cussing:

I therefor took my cheap M5 die and pressed it onto the crank axel with the headstock ram, in order to have it square so to speak, while I turned the chuck with my hand. It cut the thread but it looks horrible. I’m sure that the problems can be traced down to the fact that I did not turn backwards every turn or so. That has never been necessary since I got those great Zebra Taps, so I did not think about using the technique on the old style die – oh well, another one for the books. Forgot to take a picture.

For the next step, I had to go back to the standard tool-holder and HSS tool. There was no place for the dead center either, as I had to do an angle taper from the 5 mm to the 6 mm part of the axel where the prop-driver. I used this great little tool to calculate the angle http://www.magafor.com/841/uk.htm

And as close as I could measure the diameters + length of the taper, I got a value from the calculator that was very close to 5 degrees. Since all values on my drawing are some very nice numeric number, I decided to try 5 degrees on my compound and give it a go. As Fools Luck goes, it was a perfect match to the prop-driver. Sorry no picture either here.

Third operation on the crank-shaft, is lapping. I had made a tool for trying fix the old crank a while back and it didn’t work. For once it couldn’t clamp the shaft hard enough to do any work and it was too short to hold a crank with this much throw (3/4” ~ 19mm) as the shaft is against the chuck. It is the middle fixture in the picture and the hole furthest away was the one that was supposed to be used. I decided that it could be reclaimed as the lapping tool. I placed it in the vice on my drill press, took a ½” wood router bit and cut out the recces (?) for the bolt. Drilled a 4.2 mm hole all the way through followed by a 5.5 mm half way through and cut a M5 here. Turned the part 90 degrees and drilled the 5.5 mm hole almost in the center and reamed it with a 6 mm reamer. Charged it with the 12 um diamond paste and now it looked as in the picture.


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