1/5th Scale Denny Improved Ericcson

[Jasonb]

With some  and  having taken place this weekend it must mean it's time to start another build thread.

Most people seem to opt for building the Rider Ericsson Engine with it's four legged "table and furnace slung below but I have always liked the look of the Denny Improved version. There is the Eisner kit available for one in 1/4 Scale but I have read of issues with the design and castings. I did get a look at the drawings for this and could see some obvious issues of fit and when I did a basic layout of it in CAD there were other things I did not feel looked right.

So I decided to go back to basics and scanned in a patent drawing so that I could "trace" it in Alibre CAD and pull the sizes directly off of that. This shows one of 5 sets of dimensions that were taken from the patent once it had been scaled to my chosen size which is a 40mm bore making the model approx 1/5th scale, this also kept the flywheel within the XY envelope of my CNC so I could cut that from a slice of cast iron bar.



I initially just drew the various rods and linkages as simple flat bars with holes at the pivot points and did a trial assembly to check how everything moved and once happy with that set about detailing the various parts that would all be fabricated or cut from solid. I found that setting them to 50% transparency and then assembling over the Patent drawing also made checking the proportions easy, sectioning the parts also made sure nothing was going to clash internally



A quick check of what materials I had in stock and what needed to be ordered and this lot arrived a couple of days later from M-machine, the main items are some flat black bar for the base plate, slice of CI for flywheel, Brass tube for displacer (did not use it) and some thick wall steel tube that will become both Furnace and Cylinder Jacket and a piece of 70mm square for the furnace base.



After marinading in brick cleaning acid to remove the mill scale the piece of flat black bar for the base was cut a little oversize and then various holes drilled and tapped.



I then made use of the tapped holes to mount the base to a machining plate and used the CNC to bring it to the correct overall size with rounded corners and also reduce the thickness where the furnace sits. I roughed this out with an adaptive path using a 6mm flat-ended cutter then finished with another 6mm cutter but this time with a 1mm radius corner which left a small fillet where the angled edge to the raised section meets the flat. and using a 0.2mm scallop between passes the angled slope will need little in the way of hand finishing to get it paint ready.

[crueby]

Off to a great start!  Am pulling up a comfy chair to watch along...   

[Dave Otto]

Cool another one  .

Dave

[gerritv]

One of the great features of CAD, drawing over a photo/canvas etc. (feature name depending on the software). Then iterating to get the assembly you need.

Patents are such a great source of information as well. The language is rather obtuse and specific, it takes a while to get used to reading them..

gerrit

[crueby]

One of the great features of CAD, drawing over a photo/canvas etc. (feature name depending on the software). Then iterating to get the assembly you need.

Patents are such a great source of information as well. The language is rather obtuse and specific, it takes a while to get used to reading them..

gerrit

100% agree on both the drawings and the patents!  And patents from way back are available online  from many countries, though each has their own  style search engine that can take a while to learn.


 

[wagnmkr]

Lots of popcorn at the ready here as well!

 

[Jasonb]

I'd best write about another part before you get through that popcorn though I'm a pick-n-mix man myself.

As the thick wall tube for the furnace and cylinder needed reducing in diameter and to save wasting material by leaving a chucking piece I made a bung for the end so I could turn sufficient length of the OD and then saw off the full length, here I'm doing the second piece having already turned and cut off the first,



I could then hold the furnace part by the outside to bore out to the required diameter, face the end and cut a short spigot to locat eit into the lower half.



A 4mm wide slot was milled across the top for two lugs that will need to be soldere don and I then made use of the slot with a piece of key steel slipped into it so I could set the slot horizontally while I bored out the hole for the flue.



I then rotated it 180deg so that the fire door opening could be milled on the opposite side as well as some small pockets to locate the hinge and latch parts that would also be soldered into place.



The furnace on these engines has quite a lot of wording cast into it and I was keen to replicate this so drew it out in CAD and used the CNC to mill away the surrounding metal to leave the letters standing proud, This took quite a while as the fine pointed engraving tool could only take a small stepover but it's tapered end did replicate the cast letters draft angle.



The furnace body was then held on the rotary table so that a pocket could be milled into which the suitable bent lettering could be soldered



The lower part of the furnace was base from some square bar, first boring out the waste material and a step to locate the spigot of the top half.



Then over to the CNC to cut the outside complete with draft angle to the sides and feet.



Then flipped the other way up to square up the cavity before milling off the excess depth.



I used a Sif type rod to braze the two main halves and the hinge/latch parts together then after a quick pickle used silver solder to do the nameplate and top lugs.



After a clean up and grit blast and the addition of the door that's about complete.

[RReid]

That brass plaque is wonderful, Jason. Another very effective use of CNC.

Having lived in Newark, Delaware for 6 months before moving over the line to Maryland for the remainder of my 15 years in that region, I can tell you that the locals are sensitive about how their town's name is pronounced and are quick to correct newcomers. It is "New-ark", never "New-erk" as they would say it in that New Jersey town of the same name.

[wagnmkr]

I used to enjoy the Pick N Mix at Wooley's in York on every visit there. We always had a bag of the stuff with us.

[redhouseluv]

I like the fire opening door; I wondered if the Stuart Boilers ever came hinged rather than cast?

[Dave Otto]

Beautiful work Jason!

Dave

[Michael S.]

Very nice job Jason. It looks like excellent soldering with silver solder.
This Sif hard solder means nothing to me.
Is there something special about soldering steel to steel?

Michael

[Jasonb]

Thanks Guys

I don't think the Stuart boilers ever had opening doors as they were always spirit fired but would be an interesting project. Maybe best to start with some say 3mm thick steel so that the hinge lugs can be silver soldered to that.

I don't know the exact make up of the rod I used but SIF is a trade name for a number of different brazing alloys which are mostly copper/zinc based and the process is often referred to as brass brazing, used on things like smooth fillet brazed bicycle frames and race car suspension where it puts less heat into the tubes than welding and the fillet spreads the load. I mainly used it as it has a higher melting point than silver solder of around 850-900 DegC which will both stand the heat from the gas burner that will be used to fire this engine and also not melt while I solder the other parts into place. It is usually used with oxy/fuel torches but I can just get enough temperature out of my Sievert propane torch if the parts are not too thick.

https://www.weldability-sif.com/products/sif-consumables/ro011601/

[Michael S.]

Ah thanks, now I know what you mean.

[Jasonb]

The water jacket started much like the furnace with the tube being held by it's finished OD so it could be bored out but leaving a smaller diameter at the far end but a similar locating spigot at the top.



Some 5mm plate was bored out a little undersize and then a larger counterbore was machined to accommodate the spigot on the tube



There is a flat down one side of the jacket and rather than cut this from solid which would have been a big lump to heat up for silver soldering I opted to weld two pieces of angle iron together. This shot shows the weld being machined flat though final machning will be done after soldering.



I then used the boring head to cut the other side to a curve to match the jacket, also did the block that the water pump fits to at the same setting.



After soldering and a pickle the assembled parts were then treated much like you would a casting, here the top plate has been bored to size and the bottom end 0.2mm smaller so that the liner will drop in most of the way before it becomes tight. The plate was also faced to bring the overall length to finished size.



The bottom just needed drilling and tapping for some bolts that will hold the hot cap in place



With the jacket firmly held between two angle plates the flat side was milled down to the correct offset from the ctr of the jacket, six holes tapped to attach it to the frame and I have just milled out the clearance slot for the flywheel with a 6mm cutter with 1mm corner radius to leave an internal fillet for that cast look.



The block for the pump was also milled down to the final projection, drilled and tapped and the water passage was also drilled and counterbored for a sealing O ring.



A bit more drilling and tapping on the top surface finishes the jacket off, this time they will hold the beam pivot bracket in place.