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1914 Dennis Lorry


BenHawkins

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I have finished machining the speedo drive parts and fitted them to the lorry. The next jobs are making the flat drive belt and flexible drive shaft. The tensioning spring is a bit too long and weak but it should be easy to sort a replacement.

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  • 2 weeks later...

I decided to stitch a leather belt for the speedometer drive. This started with a hole pattern and scribing lines as described in a lathe manual.

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Then stitching in-situ with waxed twine.

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And finally putting it in place.

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To make the speedo cable I turned up some brass ends and soldered them on to some 1/2" brass flexible conduit I purchased at an autojumble. Steel ends were turned up for the inner and crimped on by placing them in a vee block and punching it down with a centre punch.

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That is another thing to test when lockdown ends. I have a speedometer app on my phone to check I got the maths right.

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I have been working through the "finishing touches". Originally there was a small brass plate fastened above the bonnet carrying the vehicle details. These survive on other preserved Dennis vehicles and I had taken measurements and rubbings in the past.

Using Computer Aided Design I was able to generate the artwork and print it onto some "press-n-peel" film. This is basically a plastic film with an emulsion on one side. It has to be printed on a laser printer; apparently some brands of toner work better than others. The artwork has to be a mirror image of what you want to retain when etching and you have to make sure you print onto the matt side with the emulsion (the CP&Co asset tags are for the other projects).

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The brass plate needs to be free of all contaminants; this was a piece of polished brass that had been protected with a plastic film so there was no need to clean it back.

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With the brass on a wooden board and using the "garage projects" iron the brass was warmed up (being protected with a sheet of paper).

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The blue film was then placed on the brass, toner side down with the sheet of paper on top and given a further ironing. The instructions warned not to press too hard or the edges might smudge.

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The instructions then said quench in water and peel off the film. Not quite the result I wanted.

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Second attempt, ironing for longer with more pressure.

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Some of the artwork was rectified with a marker pen and I inked in the back so it would not be etched. It was then immersed in ferric chloride for a couple of hours.

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Finally it was washed under running water.

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Just caught up on the last couple of years of this project, what a very fine job you've done, and all so nicely documented.

I'm sure you already do, but if not, you have my permission to feel very proud of your achievements.

Bernard

Edited by gritineye
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  • 2 weeks later...

I would like to thank everyone for their support of this project. I know it does not completely fit the military theme of the forum but hope that it has been of interest and useful to other people attempting similar restorations.

To answer the question about etching, the toner protects those areas from the ferric chloride. I obviously didn't get it perfectly adhered as there was some shallow etching behind the toner (simulated patina?)

Following the etching I cut the identity plate out and painted it black. Fine silicon carbide paper stuck to the back of my steel rule was used to polish it back to reveal the raised areas before stamping the numbers. Two of the fields are left blank; I will stamp them if I ever find out the correct numbers (when new). I believe both numbers were a little bit below 800 from surviving Works Production Orders. The number is on the axle somewhere but obviously I don't have the original gearbox.

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Six weeks ago I did the artwork for the tread plate and sent it off for manufacture. I am lucky because the original drawing survives, it could have been made from that but I didn't want to pay someone else to have the fun. There are plenty of etching services available to do this sort of thing but I wanted some for both of my Dennis vehicles with a deep etch and someone who could deal with a CAD format (such as DXF) rather than a Corel EPS. Originally I tried some steam model people but ended up using a machine nameplate company in Scotland. They worked out at £27 each (delivered) and their production line laser cuts the profile and does the blacking and flatting back. All that was left to do was countersink the holes and screw it down!

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So that is two ways to get the job done. The tread plate is bigger than the transfer paper so would have been more difficult for me to do, also I wanted a few of them so was able to split the cost of the mask they have to produce.

I am running out of things to make for this vehicle; it's been fun and hopefully we can get it out a bit more in the near future - the speedometer calibration needs testing!

 

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Ben, I normally use the dry film resist material rather than relying on toner transfer. It certainly is quite tough and allows for long etching times if you need deep etches. I also have had good success with the brass chemical blacking solutions as an alternative to black paint. It will never flake off!

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On 4/10/2021 at 10:21 PM, Asciidv said:

Ben, I normally use the dry film resist material rather than relying on toner transfer. It certainly is quite tough and allows for long etching times if you need deep etches. I also have had good success with the brass chemical blacking solutions as an alternative to black paint. It will never flake off!

Thanks Barry,

I was keen to avoid the UV exposure and developing stage of the process so gave the toner transfer a go. There is a light box I can borrow but it is too small for the tread plates. I might give the dry film a go for the ID plate on the 1908 Dennis; that one is a slightly different design and it is always fun to try another method.

 

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