Well, you know that sinking feeling you get when you notice something doesn’t look quite right? Well, I got that feeling yesterday after I posted my update. I was watching the video of the ratchet wheel turning the pump crank and it suddenly dawned on me that the pump plunger was supposed to be under the crank pin during the downward stroke of the pump. The downward stroke is the one that will be under the most load, since it’s squishing the oil, under pressure, into the system.
And what you’ll notice in the video is that the crank pin is FAR from the plunger on the downward stroke.
What's going on?
So, I spent some time investigating this today and found that I’d drilled the hole for the pump body on the wrong side of the pump housing. It is supposed to be offset 1/16” to one side. I just happened to get the wrong side. How’d I do that you might ask? I certainly asked that question!
Turns out that the diagram for the pump shows the hole from the TOP, not the BOTTOM, which is what I’d assumed. So the offset happened on the incorrect side.
This is at the start of play today – the crank is moving up (sucking oil into the chamber, not under pressure. But the crank pin is close to the plunger. This is backward.
What to do? After cogitating on this overnight, the plan I came up with was to silver solder a plug in the hole and re-drill. I thought it sounded like a great plan, so I got to work.
Here’s me turning the plug from a piece of CRS.
Here’s the housing, the plug, and a couple of pieces of sheet steel that I grabbed out of the scrap bin to use to cover the glass. My hope was that by covering the glass with the sheet I could avoid breaking the glass during the silver soldering. Solid plan, right?
Here’s the part setup on the operating table, ready for the repair work to begin.
I used black flux, which I always use on steel and larger parts since it takes longer to get them up to temp. You can see just a bit of the solder ring sticking out of the black flux along the top of the plug. I’d made a few dimples in the plug to help keep it centered and to provide enough friction that it wouldn’t fall out during soldering.
The soldering operation went great! But the glass came out cracked in the end. Ah well, I’ve got another 97 microscope slides that I can use to cut a new piece of glass for it.
Here I’m set up in the mill, just getting ready to shave off the bottom of the plug. I didn’t pickle it very well… I was too impatient.
But it’s clear that the solder penetrated the repair joint quite well! I’m pleased!
And then I had to mill off the top of the plug on the inside. No before picture here, just the after.
Now, to drill the hole for the pump body in the CORRECT place this time. You can see the faint outline of the plug I soldered in place – it’s only off from the correct hole by 1/8”. It was supposed to be offset 1/16” from the center line. I went the wrong way the first time. So going 1/16” the correct way this time, makes 1/8” total. That looks promising, doesn’t it?
And here, to compare with the plans. I wrote “TOP” on this picture now – I guess for the NEXT time I make one of these
. But you can see how if you interpreted this view to be a BOTTOM view, the hole would be on the opposite side of center. Ah well… Live and learn (he says optimistically).
And here’s the after picture. I decided not to put a piece of glass in till after I’ve painted the housing. I was worrying about how well the glass would survive the powder coating oven anyway. Nothing else on this unit will be painted. Well, maybe the pawl bracket and/or lever.
And here are the before and after pictures right next to each other – hopefully, this makes it more clear on how offsetting the plunger on one side or the other affected things. The picture on the left is the BEFORE shot. The crank pin is on the way UP and is more closely centered over the plunger (this is backward). The picture on the right is the AFTER shot. The crank pin is now moving downward and is closer to the plunger, which is CORRECT since this is the stroke that requires more power – pushing the oil into the system.
Note that the plunger cam follower thing (scotch yoke) is also reversed in the before/after pictures too. That was another clue that things were wrong.
But I’ve got it turned around now. And all it cost me was a day’s effort in the shop!
That’s a bargain, right?!
Kim