Slapper

[PaulR]

After drawing up some more of the plan I thought I'd make the four legs for the crosshead guide but the garage was a lot colder than I expected. As a result I only made them to exact length and had to knock it on the head to due frozen fingers

Don't bother clicking on the photo, there's nothing to see 

[PaulR]

Finally got my hands on some suitable steel sheet today so I marked out the holes for the parts I've made so far, taking measurements directly from the plan. All looked well until I put the actual parts over the punch marks to check everything and discovered that I'd put the holes in the four brass strips about 1.5mm too far apart  No idea how I managed that but they might be salvageable as those holes are under size anyway, if not I'll make some new ones.

[PaulR]

Shortened the inlet tube then drilled some holes in the base-plate. Considering the state of my pillar drill I was amazed to find that they all lined up  Despite that I've decided that I'm going to disassemble the drill after completing this engine to see if I can improve it - if I put a small drill in a centre punched hole and press down gently the drill bit tilts to one side!

Made two of the hex posts to support the cross head guides then decided to change the design, making them shorter, female threading both ends and having screws coming in from the top instead - much easier than turning down half of their length for threading. Next job will be to see if I can adjust the position of the holes in the brass bits to line up with the 3mm hex head screws and make some tubular spacers. After that it'll be the valve/rod and its supports which will be where the two nearest holes are.

I haven't even considered what will be going on at the crank end of things yet but hopefully the 8" long plate will be plenty long enough to fit things in!

[PaulR]

Got a very sore forefinger from using my smallest needle file to move the eight holes over to the correct position and correction the small bit of lateral error at the same time. Also made the first of the four spacers which are 4mm dia and 4mm long with a 3mm hole up the middle. It was very fiddly getting the tube to length (I've left about 0.1mm excess so they don't allow the bars to clamp the rod when fully tightened down. Here's the current state of things with one spacer in place on the right.

[PaulR]

Finished the tubular spacers. Started on one of the valve rod guides which is 1/4" brass with a reamed 3mm cross hole, just need to turn it to length and thread the bottom for fixing. Not having a mill, rather than turning to length then drilling the cross hole I've come up with a dodge:


• make the part a bit longer than needed and drill/ream the cross hole in about the right place (using a bush made from the same rod)
• put it in the 3 jaw with a rod in the cross hole to butt up against the jaws
• remove the cross rod and use the feed dials to measure from the jaw to one end of the part
• turn to length then flip it over and repeat

[vtsteam]

I like it when you find a solution to use the lathe, lacking a mill, to do accurate sized squarely located work like that. Many hobby engine builders of the past had only a lathe, and did remarkable projects, often with faceplate and angle plate alone. I really enjoy reading about and trying that kind of stuff.

Looking good! 

[PaulR]

I like it when you find a solution to use the lathe, lacking a mill, to do accurate sized squarely located work like that. Many hobby engine builders of the past had only a lathe, and did remarkable projects, often with faceplate and angle plate alone. I really enjoy reading about and trying that kind of stuff.

Cheers, you have to admire those who came before and managed to produce fine work with limited machinery and hand tools.

I used the above method to finish the two posts in today's short session and happy to report it worked well. Here they are with a bit of (toasted!) steel standing in for the as yet unmade valve/rod which will be the next task.

[PaulR]

Slight setback today. I made the business end of the valve and fitted it to the rod only to find that when everything was assembled the rod was impossibly tight in the brass guides made yesterday. When I looked at the thing side-on I could see why - the base plate isn't flat in the x or z axis! I'm guessing it's been guillotined, bending the ends in the process. I tried to straighten it by hand (clamped between wooden blocks and 'encouraged' with a mallet) and managed to improve things somewhat. However, I think I'm still going to need some shims/washers to lift the guides about 0.25-0.5mm. So I started to make some from 3/8" brass, initially about 1mm thick, which I'll sand down as required. Annoying  Meant to take a photo of the assembly but forgot so here's a 'parting shot'

[PaulR]

After much fiddling about I managed to get the guides looking the same and the rod moving reasonably well. I think they also look a bit better as proper stanchions rather than simple posts. Next will be the little stops that sit on the rod (the slapees so to speak  ) and the combined cross head/tappet.

[PaulR]

Only a tiny bit of progress today: made a pair of danglers  but need to shorten the screws

[vtsteam]

Wish you'd stop throwing that technical terminology around. 

[PaulR]

Wish you'd stop throwing that technical terminology around. 

Sorry Steve, that was a very lax description, technically they're 'dangly clackers' 

[PaulR]

Oh wow  , I just realised I've created a masterpiece in the manner of M C Escher - those little parts look as though they're fixed to the base and the rod!!! Magic danglers 

[PaulR]

Almost finished the cross head today. Doesn't look like much but quite a few careful operations for its size 1/4" square and 22mm long: turn to length, centre drill each end and thread one M4 for the piston rod, drill and ream the 4mm cross hole for the 'whacker' (another technical term, probably should be the 'activator'?), mount in the vertical slide and slot drill the clevis, cross drill and thread one side M3 (should have done that before cutting the slot but forgot  ). For that last op I inserted a 3mm packing piece to eliminate the risk of the clevis closing up when punched/drilled/threaded and it all went fine.

Need to decide how to fix the activator rod, will probably go with Loctite but might solder it - the final rod will only be about 19mm long not like the long temporary piece in the photo (temporary screw in that photo too). Might also round the ends of the clevis so it's a bit less ugly.

[PaulR]

I loctited the activator rod but when assembled it's a gnat's whisker too long and touches the valve rod rather than just missing it so I'll need to reduce it a little. I also made the crank, using Jason's method (https://www.modelenginemaker.com/index.php/topic,12683.msg301940.html#msg301940) although it would be awkward to set that up in the vertical slide so I scribed the lines while it was in a drill press vice then put it in the bench vice and sawed and filed it to shape. Here it is after a bit of tidying up as well. I much prefer the matte appearance to shiny, I'll try to get the outer surface the same, maybe using some grinding paste??