Bog's Paddleduck Engine

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kvom:
I did a few calculations around the crank webs and the connecting rod. I have access to a goodly amount of .25" thick brass plate, so I'm planning to cut the webs from that, although proportionally it's undersized. Given the spacing between the pillow blocks, the crank end of the connecting rod would need to be increased somewhat, to ~.45". Since I just ordered a stick of .5" square brass rod, that seems the way to go.

So this morning I cut out a roughly 1.8" square of the plate with a hacksaw, drilled a 1/4" hole in the center, and turned it down on the lathe using the same clamping method as for the eccentric. It took a few tries to figure out the best clamping method, but eventually I arrived. It would be quicker all around just to mill out the discs with a rotab, however.

bogstandard:
Kvom,

I couldn't understand the way you are going to take up the missing space, so either make the crank blocks longer (expensive), or put a spacer in between the crank webs and blocks to take up the side slack.

John

kvom:
On the plan, webs are 5mm and conrod is 6.5, so 16.5mm. Scaling up this gives .974" of material. If my webs are .25" each, then the conrod end would be .474" to give the same spacing. This is opposed to the .384" it would normally be. Since I'm starting with a .5" square bar, I won't need to add a spacer.

***edit***

I made the second disc using the Palmgren (copy)? rotab, cutting it out using a 1/8" 4-flute endmill, the smallest I own. No real problems, other than the usual hassle of clamping small pieces with big clamps and bolts.

I'm now out of pieces large enough, so will need to resupply on Monday night. I think I know a better way to do the other two.

I'm wondering if the 1/8 endmill is too wide for slitting the webs? Opinions?

sbwhart:
Try a 1/16" slitting saw if you've got one, it would look more in scale.

Stew

kvom:
I spent a couple of hours in the shop after dinner starting on the packing gland.

For the screws, I decided to use a diameter of 15/32 so that later, when I need to turn the flange to fit the cylinders and drill for the piston rods, I will be able to hold the glamd in a collet rather than the chuck. The thread is 3/8-16. I had no real issues turning the screws as I had a piece of 1/2" brass rod to start with.

I then turned the gland itself, with the inner diameter 15/32 to match the screw, and the outer diameter 1", turned from a piece of 1" brass rod (took .001 off for finish). Then drilled and tapped to match the screw. After parting there is enough extra length left to turn the inner boss for the cylinder bore.

My only "problem" is that the screw won't go in all the way, because the tap won't cut enough threads (pointed part is too long). If I can find a bottoming tap at school I'll fix it that way; otherwise I can always shorted the screw portion.

Thoughts?

I finished only one gland, so the other is on the agenda for next time.

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