Bog's Paddleduck Engine

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sbwhart:
Thanks Bernd

That sorted me out :thumbup:

Stew

bogstandard:
Ron,

You can go as large as you need to, but keep an eye on the flange mounting screws at the end of each bore, don't go too close to the screw holes as they might weaken and strip out if you get too close. Just make the spigots on the flanges to fit the larger bores and of course, the pistons.

Kvom,

Be very careful machining it if it is beryllium copper, it releases some nasty things when machined under certain circumstances. I would have a look on the web for info on how to treat it while machining. It is always better to be on the safe side.

John

kvom:
I don't have much to show for 4+ hours of work.

My first goal was to mill the brass to size for the conrods, but I was having all sort of problems with the finish. After changing endmills a few times without success, I noticed a little light on the control panel of the VFD : rev. I had been running the spindle in reverse. :hammer: This is not something that would be likely to happen using the normal mill switch. Either I left it in reverse after boring the eccentric straps in back gear, or I fat-fingered the button (which is right above the run button. As I was running the mill at 2000 RPM I didn't really notice that it was turning back-asswards.

So after wating a fair amount of time I did manage to mill the brass to size, center drill the ends, and drill/ream the holes at 1/4". My intention is to turn the conrod like John's, between centers. Since I need to borrow a lathe dog from school to do this I'm leaving the rest of the milling for afterwards.

I then decided to make the crosshead guide bars from some 1/4" drill rod. After some calculations on dimensions I settled on drilling and tapping the ends for 6-32 screws. Rather than mess around with the collet blocks to hold the rod, I switched to the rubberflex collet chuck. Drilling the rods was not much of a problem. However, when I attempted to tap the first one still chucked, I broke my automotive-quality tap off in the hole. I was able to extract the tap, and decided to tap the rods later using the mill as a tapping station. This rod didn't take will to parting either, as once the parting bit is halfway through the rod snaps off, and also causes the chucked end to bend at the chuck jaws. So after the first one, I just used the DRO to mark the length, parted just enough to show where to cut, and cut it off with a hacksaw.

Now that I had the 4 drilled pieces, I proceeded to tap them at the mill. The first two went fine, but on the third I snapped off my only remaining, good quality, 6-32 tap. So that was then end of that for now. :bang:

I decided it was time to take a break.

Perhaps I need to anneal these rods before tapping!?

Darren:
Thank you for posting that, I was feeling quite left out.......... :ddb:

Amaizing how it still mills backwards.... :doh: But you look like you are winning :clap:

kvom:
This morning I attempted to machine an eccentric coupling fork. Unfortunately when I started to mill the slot I discovered that a 1/4" slot is too wide. It scales to .236. And in addition my 1/4" end mill is slightly oversize as well. So on to a redo with the 1/8" endmill. On the bright side I came to undestand that it's quicker to square off the stock for both forks at the same time and then cut them apart. :smart:

I had an excellent trip to school this afternoon to discuss my engine issues with the instructor, and to borrow some needed gear. So to total it all up:

- He recommended that for tapping the drill rod for the crosshead guides, I should drill the hole with 1 or 2 sizes up on the drill bit and somewhat deeper. That will lessen the chance that I will break the tap (and I got a new tap to try it with).

- borrowed a 1/16" slitting saw on an R8 arbor for slitting the crankwebs. Here he suggested that clamping all 4 of the discs together and slitting them at one time might make for a more rigid setup. By leaving the pins in the holes used for milling level, the setup can be the same, and the pins removed as the saw blade nears the hole. He suggested slow RPM and slow feed.

- Borrowed 2 lathe dogs for turning the conrods between centers (looks as if either will work). I also got a piece of steel from which I plan to make an adjustable dog that fits my chuck.

- scored a piece of brass plate 1/4" x 3" x 8" that will serve to make the bottom plate, the 4th crankweb, and some of the other smaller plates as well.

- Found that the block of mystery brass alloy in my lockers is large enough for the block, and possibly even two of them. Another piece of the same allow can make all 4 bearing blocks.

- The 2" round silver brass that Cedge gave me will get a slice cut off for the flywheel.

So it looks as if I am set for material except for the top plate. But there is a fellow on eBay who sells pieces that will be suitable.

Nothing stopping me at the moment but lack of energy. :whip:

Here's the result of the evening's efforts. Two forks for the eccwentric coupling. Haven't drilled the holes for the pins as yet.

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