MadModder

Here I've glued in the foam bits I needed to correct the pattern. I used offcuts of fanfold foam, which has a somewhat different texture and density than the regular Dow foam I made the rest of the pattern from. This may show up in the finished part. Probably will....

 

Then sanded again...

  

Then I added a sprue that I just shaped by hand out of a piece of foam. Again, more foam dust, only this time I moved outside on the porch to do it. Nevertheless, static electricity tends to stick it to you and everything else nearby. even in a breeze, as there was. The sprue was attached with hot melt glue, since the joint was irregular shape and hot melt is good at filling in small gaps -- unlike rubber cement, which produces a very thin glue line.

 

It's been a really long time since I did a lost foam casting. As many of you know I'm pretty much a dyed-in-the-wool conventional greensand caster. And I actually like making wooden patterns -- maybe as much as casting metal itself.

Nevertheless, there are some things you can do with lost foam that are difficult or impossible with conventional casting. Complex undercuts, deep draftless and narrow dimensioned parts, and big changes in dimension with a resistance to forming shrink cavities.

The drawbacks to lost foam are foam dust, foam melting fumes, the need to make up a new pattern for every part cast, more rapid contamination of sprue and supporting metal for remelting, and very different orientations and methods for getting sound castings. I don't find lost foam casting pleasant. But occasionally it serves a purpose, at least for me.

So this time, I wanted to give it a try again for a water-cooled hot air engine block casting in aluminum. This is an adjunct for my No. 83 engine experiments. If I build a much larger engine in the future, lost foam casting may become important to reducing the thickness and weight of aluminum needed, compared to a model sized engine.

For the present, I'm still working with an average 1" bore size engine, as a test of lost foam methodology. I drew up the shape I wanted in the old free Google SketchUp and then through a long series of graphic transformations got that shape into a cutting file for my old foam wing cutting software, JediCut. This runs on my CNC hot wire foam cutter.

I won't go into all the work I had to do just to get that shape to cut, but it was NOT the most fun part of this project! I could have made 10 wooden patterns by hand in the time I spent eventually getting one CNC foam pattern cut

Anyway, here it is, finally....with some flaws. There's a piece of excess at the top, a bad lower left hand corner (defect in the scrap foam piece I was cutting from) and two gaps where the wire had to cut through to get to interior hollows. Those will all be plugged with glued foam bits.

 

Little more progress:


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I found that Lesu makes a driveshaft with a 40-45mm range.  I initially had 37mm between the center axle and the rear axle.  If I add 5mm to my center/rear axle spacing that will put me in the middle of the Lesu driveshaft's range.  I did some checking, and the only 3D printed part that I really need to modify to do this is the equalizer beam.

Eventually I will have to determine the hole sizes/locations for the frame rails, but that's a problem for future me.

Don

Good evening all

After finishing Wilding`s Tower Clock, I started a new build over the last two weeks, Bernard Tekippe`s Simple Regulator. It has quite an interesting arrangement around the escapement: unlike traditional clocks where the pallets are mounted on an arbor connected to the crutch, in this design the pallets are mounted directly to the pendulum. That means the escape wheel impulses the pendulum directly. Tekippe showed he had some amazing accuracy with this clock, better accuracy than other more complex regulators!

I have spent some time collating as much information as possible on this clock and was lucky enough to meet a clockmaker who visited the USA in 2010, listened to Tekippe present and managed to take hand sketched dimensions of his clock. There is also a NAWCC article by Tekippe as well as another enthusiast, Steve, who has done a fantastic job of creating some 3D models of the clock. I`m using a combination of the hand sketches, original article and primarly Steve`s CAD drawings, to try and make my version of this clock. Accuracy of time keeping is not at all a concern right now, I just want to get a replica running as a tribute to Bernard. If it tics, I`ll then start trying to get some fine tuning of the time keeping.

I`ve just had a couple of weeks of work and managed to get quite a bit done....







I hope this is interesting to some of you. I know there don`t seem to be lots of clockmakers on this forum but I thought it might still be interesting to some of you. I only do the videos for fun to document my build - I don`t pretend to be an expert. 

Chris