And last but not least, the support that the cylinder sets on. Its kinda tricky, because there is an angle on all four sides.
Brian does Popcorn
- Thread starter Brian Rupnow
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Whoops!!! Forgot the main base!! I haven't built this yet.
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Great set of drawing Brian:- I've PM you about them
I don't know how your planning to do the cross head guide but if you're going to use the fixed steady method i used just a word of warning, check out the steady that it bolts down secure to the lathe bed, the steady that was suplied with my Chines lathe was a load of crap as suplied, in fact I would say it would have been dangerouse to use. I modified mine by bolting a chunk of ally across the base to make a wider more positive base with tapered pull ups, that fixed it securly to the lathe bed, can't post pictures of it at the moment.
Stew
I don't know how your planning to do the cross head guide but if you're going to use the fixed steady method i used just a word of warning, check out the steady that it bolts down secure to the lathe bed, the steady that was suplied with my Chines lathe was a load of crap as suplied, in fact I would say it would have been dangerouse to use. I modified mine by bolting a chunk of ally across the base to make a wider more positive base with tapered pull ups, that fixed it securly to the lathe bed, can't post pictures of it at the moment.
Stew
I forgot these two guys.--I built them this afternoon after wife and I went out for a drive to see the autumn leaves. Wife had a nap, I played machinist. (Wife is far brighter than me!!!)
sbwhart said:
My lathe will take up to 1 3/16" thru the spindle, so I SHOULD be okay to make the crosshead guide without having to use the steady rest. Thanks Stew, for the warning.----Brian
I spent a very entertaining day today, machining the crosshead guide. I started out with a 1 1/4" round peice of cold rolled steel, and I turned, and I drilled, and I bored, and I reamed, and, and, and. I actually got to use a couple of peices of kit that up untill today were primarily dust catchers. I have no idea why I bought such a huge height/marking out gauge. I must have thought I would be machining full sized locomotives when I bought the damn thing 3 years ago. The little V-block with clamp is a fairly new "impulse" buy that I bought 6 months ago on a trip to BusyBee Tools, looking for something else. I bought a new 5/8" ball nosed end mill to put the radii in the crosshead guide with, and it worked well, but I found it rather terrifying to use. I was taking a 0.276 deep cut from the side, feeding in about .015" at a time, and the THUMPA-THUMPA-THUMPA and vibration had me wondering if it wouldn't be a much better tool to use on a full size Bridgeport rather than my little Craftex unit.
I've gotten this far, with only one "gotcha". I have been warned numerous times about the folly of holding an end-mill in a chuck, but I have never found it to be a problem when cutting brass or aluminum. However, the crosshead guide is made of steel, and I had a BIG end mill in the chuck. As I was machining one side, it seemed that the mill was working harder, and harder and Oh Oh---the cut is getting deeper and deeper!!! Hit the kill switch, clear the chips, and Damn----the end mill came loose in the chuck and was dropping down farther and farther into the cut as I went along. Far too much work invested already to start over, so a quick trip out to the garage, fire up the mig, and weld up the ever deepening cut. Then 20 minutes of file work. Now nobody will ever know but us!!! Tomorrow I will endevour to but that humungous 0.787" radius in the last side to be cut away (Not exactly sure yet just how I'm going to do that) and the crosshead guide will be finished.
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Good work so far. Maybe the radius cut can be set to .75 and just use a 3/4 endmill. The endmill in a chuck for milling problem is a good lesson to learn (of course, a chuck CAN be used when drilling/boring with an endmill).
In looking at the plans, it seemed to me that the valve gland could be lengthened enough so that the little support piece wouldn't be needed, and then getting the support's height exactly would no longer be a problem.
In looking at the plans, it seemed to me that the valve gland could be lengthened enough so that the little support piece wouldn't be needed, and then getting the support's height exactly would no longer be a problem.
Kvom---a 3/4" endmill cuts a 3/8" radius.
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Brian Rupnow said:
oops, my bad. :-[
Today, I had to build a part to finish a part. The crosshead guide for the popcorn engine is one of the trickiest parts I have built so far in my machining hobby. The first two cuts were accomplished without too much difficulty, but the last cut with that 0.787" (20mm) radius had me worried. I finally decided to cut it with the boring head in the mill. In order to do this I had to machine a holding fixture from aluminum and bolt the semi finished crosshead to it. The largest part of the cut-away was accomplished with the bandsaw, but even for that the part needed to be held in some type of fixture. I am very pleased with the results, and will post a picture if I can. Photobucket is being very oinky tonite for some reason. My digital pictures are not as focused as I would have liked, but they will suffice to show the boring operation, the fixture block I had to make, and the finished part. All I need to do now is spend some quality time with a bit of emery cloth and I will be able to move on to making the base. I still haven't done anything about a flywheel, but that is the only part remaining to be made, other than the base.
This is a couple of shots of the completed part still bolted to the fixture block.
And here is the finished part, just waiting for some final sanding and de-burring.
Thanks stew. I don't always get consistent results with a file----seem to have a hard time keeping things level. It certainly is an aquired skill!!! Here is a drawing of the four feet that go beneath the main base. Since I am using a larger diameter flywheel, it actually hangs below the base a bit.
Well, I have a great lot of parts!!! Most are finished, some "semi-finished". I just whittled out the base this afternoon, but it needs a fair bit of sanding and de-burring yet. I haven't done any more with the crosshead guide. All I lack now is a piston, a flywheel, and the four feet to go on the bottom of the base. This will be a nice little engine, but I wish I hadn't built two engines so close together. I'm finding this one more of a chore than the Overcrank single, not because its any more difficult, simply because I do better if I wait about 3 or 4 months between builds.
Could this possibly be the last drawing? I got up this morning and made the four "feet" that go on the bottom of the main base, then realized that I had enough 5/8" dia. stock left to make a piston. Then i realized that I hadn't yet made a drawing of the piston. So---Here it is.
I had to make this drawing to establish all of the correct set-up lengths for my linkages, so will include it in the complete set. I am going to lose my computer for a week or two, as I have taken a short term engineering contract where I absolutely MUST be "on site" along with my mega computer that hosts my solidworks. My crummy little lap-top is about 6 years old and is way underpowered to run Solidworks on now. I will save all my current popcorn drawings as .pdf files and put them on a disc so that I have access to them on the laptop while my big computer is away. I don't like to do this, but after a wonderfull summer of "Fun in the Sun and no work" I have to do something to refill the kitty!!!
