1/5th Scale Denny Improved Ericcson

[Jasonb]

I was in two minds on how to make the "frame" structure that supports the flywheel and side levers - laser cutting would have got nice interernal corners but as I have the CNC that was also an option and I could always square up the corners with a file.

In the end I decided to use the CNC which did not work out as I had hoped, all was going well on the first piece then the swarf suddenly started to come off red hot with some sparks which took the edge off the carbide cutter but it carried on just throwing up a bit of a burr. The next time it came to the same part of the cut it was sparking again and then really struggled and broke soon after. Put in a new 3mm carbide cutter and it happened again. So looks like there was a hard inclusion in the 2.5mm steel sheet which I have had a couple of times before with steel.

Rather than buy some more 2.5mm sheet and replacement cutters I decided to produce the files and sent them off to Lasermasters who sent these back within a week.



The base and vertical plate were milled up from 5mm sheet without incident as was a piece that will be machined to form the pads that the two bearing pedestals bolt to. These were then wired together and silver soldered.



After a quick sand blast they cleaned up quite well with the solder having flowed well down the inside corners and out into the joint, just a few small gaps where the tabs did not completely fill the matching notch and the solder could not bridge the gap.





I could now start machining it so fixed it to a machining plate which was clamped to the lathe cross slide so the bottom that was left over thick could be cleaned up and brought down to the right thickness.



Then over to the mill to finish the edge of the base and I also skimmed the ends of the bearing supports to the same hight (more to come off them later)



That gave me three points to sit on the mill table so the vertical plate could be milled square to the base as well as drilled & tapped.



The bearing supports were then milled to height and their ends trimmed to the final length as well as drilling and tapping for the pedestals.



Lastly the arm pivots were milled to length and drilled & tapped for the pivot pins.



Quick trial fit and all look well.

[gerritv]

Designing the tabs in must have saved a lot of fiddling to keep things aligns. Looks very solid structure now that it is essentially one piece.

gerrit

[Dave Otto]

Looks great Jason!
Did you solder the whole thing with one heat?

Dave

[Jasonb]

Yes the tabs do help a lot, the wire was almost just belt and braces, there was very little difference in the thickness of material milled off the bottom and vertical plates so it must have stayed quite true.

Yes all done with one heat, I worked half way down each corner in turn feeding the rod into the inside of the joints and then round again to do the lower half and finally the bottom. I did use HT5 flux which lasts longer than our standard ones.

[fumopuc]

Hi Jason, I do enjoy the different machining set up´s.

[Jasonb]

The hot cap started life as a short length of stainless steel exhaust pipe which can be had in many different sizes on ebay. A disc of stainless sheet was Sif brazed to the bottom and a steel ring silver soldered to the top to form the mounting flange. After soldering the flange was skimmed down to final thickness ensuring it's face was then true to the axis of the tube.



The flywheel was machined from a slice of 140mm diameter cast iron, here the first side has been faced, the OD finished and the hole bored for the crankshaft.



It was then reversed in the chuck, set to run true and brought down to final thickness.



It was then over to the CNC to give it a bit of shape. I've done quite a few flywheels now and the method I have found to work th ebest is to mount the ER32 Collet with backplate onto the table and hold a piece of suitably sized drill rod in that which keeps the location of teh ctr of the flywheel. I can then mill one side and flip it over to do the other and only need ensure that the rim of the flywheel lines up to a mark to index the rotation.



The flywheel is packed up on a couple of 1-2-3 blocks and clamped down. I use the clamps the opposite way round which reduces the height they stand up above the flywheel which means I can run shorter tool stick out with out risking the collet chuck hitting a clamp.



While I was at the CNC I machined the bearing pedestal tops and bottoms from aluminium Then screwed them together to drill and ream the holes on the manual mill



The bracket that the beam pivots on is a "u" shape which I fabricated by milling the inverted tee section and then silver soldering two end pieces to.



The holes for the bronze bearings could then be drilled and reamed, the vertical ends shaped and a notch milled out to clear the flywheel.



A quick trial assembly to see how it looks so far, next will be all those links and levers.

[gerritv]

With the solder fillets that brackets looks cast. Very pleasant effect.

gerrit

[Jasonb]

Thanks, that is the aim. The "Tee" section was rough milled and then I changed to a cutter with a 1mm radius so that produced the fillet along the length, solder fillet just at the ends. It has had a bit more work since the photo to round off the external corners with files and the Dremel.

[Jasonb]

The two "T" shaped links either side of the engine are the most prominent so I decided to tackle them first. There would be a considerable waste if they were cut from solid as that would need to be 16mm thick due to the central pivot, even if I added material to the pivot so that I coudl cut it from 8mm thick plate the tee shape meant there was going to be a lot of waste. So I decided to fabricate the basic Tee and shape that then add some additional material to thicken up the boss.

The first job was to square up some strips cut from 180x 8 flat black bar and drill holes for locating dowels to keep the parts in position while they were silver soldered.



After a quick pickle I drilled some 3mm holes to use to hold the work down, only the one at the junction is going to be used , the others are in the waste material of the overlength pieces.



The much used machining plate was clamped to the table of the CNC and 4 matching holes drilled and tapped M3, actually I did 6 holes so the part could be flipped the other way round to machine the opposite side. This photo shows the arms screwed down and having had an adaptive cut to remove most of the waste material, leaving 0.3mm for the final cuts. 4mm 3-flute cutter used.



I then did a "scallop" finishing path with a 4mm ball ended cutter stepping over 0.2mm per pass which gives an almost paint ready surface, just a bit of needle file work due to a small amount of Z axis backlash where the cutter changes vertical direction.



After shaping both sides the smaller holes were drilled and tapped and the larger pivot hole reamed for a stepped extension piece.



Here it is in place after JBWelding on the boss extensions and giving it a shoe shine with strips of emery. The counter balance weight was made from two halves so the tapered internal slot could be milled before soldering together and given a final cut to bring them it size.



The links from crank to Tee and from Tee to beam are basically the same except for being a different length so were all done as a batch. First some brass was milled down to overall size then drilled, reamed and slots cut as required



These were then screwed to a waste block and the cuc used to reduce the central section in both width and thickness leaving the rounded and filleted junctions to the ends.

[Dave Otto]

Nice progress Jason!

Dave

[bent]

Wow, what a neat build so far! 

[Jasonb]

Thanks for the comments.

The next thing to be done was the beam that ties everything together. I started with some 2" x 1/2" aluminium flat bar and drilled & counterbored some mounting holes in it so it could be held to a machining plate. I also drilled in from the sides for some of the pivot pins while it was a nice easy shape to hold. With it then bolted down to the CNC's table I removed the majority of the waste from one side with an adaptive tool path, this leaves quite noticeable steps much like the contour lines on a map except these were ar 1mm height increments.



Changing to a 4mm diameter ball nose 4-flute cutter a "scallop" tool path was used to refine the shape, the tool stepping over 0.2mm per pass leaves very little handwork to complete.



The material was then turned over and two similar paths used to machine the opposite side.



Back to the manual mill and with a 6mm cutter the material that had been used to hold the part was separated leaving just 0.25mm thickness at the bottom of the cuts which could be cut through and the surface cleaned up with a file.



A bit of rounding over of the right hand end and that was another part crossed off the list.



The last shapely link required was the one from the end of the beam to the top of the pump rod. I milled a piece of brass to size, reamed two holes and slotted the ends manually before using a similar process to the beam to shape the ends and fish bellied central section.

[Admiral_dk]

Another batch of nice looking parts 

Per       

[Jasonb]

Thanks

The piston started life as some 45mm continuous cast bar, I turned the OD to fit the previously machined liner and cut a groove where the piston packing goes leaving material beyond that to form the upper link lugs from. Like the Heinrici rather than trying to hollow out the piston from above I removed most of the material from below and created a shallow recess that a disc of cast iron could be pressed into to form the bottom of the piston.



The CNC was then taken advantage of to machine the top flange of the piston with its two flats and leave the lugs standing proud. I also did the eight holes that are used to hold the packing retaining right at the same time though they were tapped by hand. After this photo the lugs were drilled and tapped for pivot pins and then the ends rounded over.



The packing retaining ring is just a simple turned steel "washer" with some holes. I'm not sure whether I will bother with any form of piston ring/packing as if the piston fit is good I'd rather have the lower friction and just run iron on iron. I will decide after test running.



As the displacer rod has to pass through the power piston it needs a sleeve and gland, this is the sleeve being turned, the diameter closest to the tailstock ctr will have a fine thread cut onto it which will hold the sleeve's flange against the bottom of the piston with a lock nut the other end will be opened out and threaded for the gland nut. There is a 4mm dia reamed hole through the whole length. Again may not need any gland packing.



The gland nut is straightforward turning, threading drilling, reaming then mill the hex before parting off.



The displacer started out as some brass waste pipe, something like 0.35mm wall (0.015") so I turned a scrap of maple to a tight fit and used that to support the tube while I held it in the 3-jaw to square off the ends. I also held it like this to Emery Coth the chrome off.



The bottom was just a piece of 1mm brass Sif Brazed in place but the top needed to be thicker to accommodate two grub screws so it's position on the rod could be adjusted. To keep the weight down I hollowed out most of this part just leaving two ribs where the grub screws would go.



<a href="https://www.youtube.com/watch?v=IpIO8n8v5Mw" target="_blank">http://www.youtube.com/watch?v=IpIO8n8v5Mw</a>

After silver soldering the top on it was given a clean up and the two holes for the grub screws drilled and tapped



The yoke that lifts the displacer via two smaller rods that come up from the Tee shaped arms was turned and then held in the indexer to mill the ends to rectangular section and add some holes. After that the ends were rounded over and slotted so the outer bolts can be used to clamp the yoke to the rods.

[Jasonb]

The build of this engine is going to take a short break. I originally made a start on it while waiting for the RLE flywheels to arrive which they eventually did so have dropped back onto that.

Also in the same delivery as the RLE flywheels were a few more castings and a couple of pre machined parts complete with special coating. Graham had sent me these after a comment I made in another thread so not being one to turn down a challenge I have designed an engine to make use of these items so wont get back to the Denny until that is done (won't be long now).

But I will leave you with this. I had enough parts made for a test run so thought why not give it a go. First I tried with a couple of blow torches aimed into the furnace hatch but that did not really work. I then removed the furnace and put a camping stove burner under her and away she went at a fair lick. Towards the end of the video you can see I have drilled a hole in the base so the burner can be placed lower down and replaced the furnace, this has slowed things down and I think blocking some of the burner holes will slow it even more. At this stage there is no water pump connected so I am just running compressed air through the jacket to keep a reasonable temperature. There are also no gaskets, piston ring or gland packing, just machined fits and in the case of the piston/cylinder some lapping.

<a href="https://www.youtube.com/watch?v=xQPEL4MIeTg" target="_blank">http://www.youtube.com/watch?v=xQPEL4MIeTg</a>