Elmer Verburg's #5 Geared engine has been on my To-Build list for quite a while. Most of the build shouldn't be particularly challenging - it has a lot in common with a couple of Elmer's other engines I've built.
The steam chest and valving layout is identical to many of Elmer's engines. The cylinder block follows the same theme, though it is a bit longer than others of a similar type; normally Elmer opted for 34.93mm (1 3/8") long cylinders, but on this engine the stroke is a bit longer, and the cylinder is 47.63mm (1 7/8") long. This is because the stroke length is dependent on the gearing - requiring the longer stroke.
My main challenge for this build will be making the internal gear. Yes, it can be purchased, but where's the fun in that
.
I'm not particularly fond of the aesthetics as Elmer's built it, so I'll be making some changes to suit my taste without altering any of the main dimensions.
Jo asked for a GA (General Arrangement), so I edited this post to add one:
For a better idea, you can have a look at
Geoff of Inky Engine's excellent example shown earlier on MEM.
As always, everyone's interaction in the build log is most welcome, be it critique, questions, or just checking in. This post is a bit lengthy, as I had a good shop session.
For the cylinder, I started off with some 25mm aluminium square bar - this is extruded barstock, so a bit gummy to work with, but worked well for some of my other Elme's engines, so will work for this one:
I cut a section off a couple of mm over-length, and used a pair of old scissors to cut some aluminiun from a discarded can of Namibia's finest lager:
One end of the stock was faced off in the four jaw chuck; I didn't bother to center it precisely; just checked the jaws against the rings on the chuck to center it approximately:
When I wanted to use my height gauge to mark the stock out to length, I found the battery flat, and no spares in stock, so I just used the digital calipers to mark it to length after colouring in the ends with a permanent marker:
I then faced that end to split the marked line - Elmer's engines are very forgiving, and for the most part there's no need to get things super accurate:
The cylinder bore is offset in the stock, so I marked the center of the bore on the stock face and used a scriber to press a decent dimple in it:
The tailstock center was brought close without touching, and I adjusted the chuck to roughly center the dot to the tailstock center:
Next I used a tailstock dead center stuck between the dimple in the stock and the tailstock live center, together with a dial indicator to center the stock a bit more closely. 0.05mm is plenty good enough here:
[youtube1]http://youtu.be/jyjICNrmu2U[/youtube1]
The stock was center drilled, and then I used a 6.5mm drill to drill the through-hole. This is the ideal type of job to use one of the "lesser-used" drill sizes from the drill set, as they get to see a bit of use for a change, as well as having the benefit that in all likelyhood those lesser used drills are sharper and will drill holes more accurately than more often-used drills:
Next I drilled the hole out to 11.8mm to ream 12mm. The swarf came off in two nice evenly-sized curls, showing that this drill also cut nice and true:
I then set up to ream the hole - A different view for a change :
After reaming the hole, I marked the face - I'll use this side of the workpiece as the "inboard" side of the cylinder. This doesn't really matter too much on Elmer's engines though; it's just one of my pet preferences:
The outside was turned down to size for a length of 6.3mm. The protective packing was sticking out a bit far, so I just turned right into it. I took a note of the cross-slide reading at final size for later:
To turn the external round on the other side, I loosened the two adjacent chuck jaws on the sides of the workpiece where the external round was closest to the sides - taking note which jaws (#4 and #1 as it happened), and reversed the workpiece, turning it so that the same sides of the workpiece would be in contact with the same jaws on the chuck. I then tightened the noted jaws - applying about equal torque as when I originally tightened them for the other side of the workpiece. A quick check with a close-fitting bit of rod in the bore, and it's within 0.02mm accurate - I didn't even bother to adjust that out:
I once again used the permanent marker to colour in the sides, and the caliper to scribe the 6.3mm width on it, and turned to split the line and down to the cross-slide reading I'd noted earlier:
Next I layed out the center of the port holes on the one side, and the longitudinal offset lines of the exhaust and mounting holes on the other side. One has to be careful here to choose the correct sides according to the plans. I didn't mark out all the holes; I'd be using the DRO to find their locations. If I didn't have the DRO, I'd have layed out all the holes:
Next on to the mill; I centered the DRO on the marked out location, and then spot-drilled the exhaust port holes:
The port holes are supposed to use a #57 drill (I don't know how you guys in the US can stand this silly naming convention
) - which is 1.09mm. A 1.1mm drill would do the job, but I didn't have one, so the other options was a 1mm or 1.2mm drill. I opted for the 1.2mm drill; the ports can do with slightly bigger holes without any ill effect. Those were drilled 3mm deep into the workpiece:
I next calculated the offsets for the intake ports, located those, and drilled 4.7mm deep with a 2mm drill in either end of each port location:
The slots were milled to depth with a 2mm slot mill - taking many light passes and blowing away chips constantly. Then the slots were milled to 2.5mm width with a couple of light passes as well:
The valve chest mounting holes were drilled 1.6mm to a depth of four mm:
Then tapped M2 using a drop of methylated spirits as cutting fluid on each:
I set the vise stop to the end of the workpiece before loosening and rotating it to the other layed out surface. Then I spotted the exhaust passage location. The vise stop kept the X center location, and I just cranked to the layed-out line by eye for the Y position:
The passage was drilled 2.5mm to meet up with the three 1.2mm holes drilled on the valve face:
The mounting holes were drilled 2.5mm to 4.7mm deep and tapped M3:
In the past, I've always used the dividing head or rotary table to drill the cylinder cover mounting holes for Elmer's engine blocks. So it was time to try something different. The workpiece was mounted vertically in the vise, and I picked up the center of the bore with a dial test indicator and set the DRO to zero on that:
The cylinder hole locations are slightly important; if they're drilled at the wrong angle, the one hole will interfere with the steam passage, so I spotted the approximate hole locations with a permanent marker to prevent a brain-fart:
Then I set the DRO to drill six holes on a 19mm PCD, and spotted the holes:
The holes were then drilled 1.6mm to a depth of 5mm:
I then tapped the holes M2 - using the collet chuck as a tapping guide and repeating the hole locations on the DRO. At that point the animals in the zoo started complaining about getting fed, so I cleaned up the workpiece a bit for a parting shot and abandoned shop:
Kind regards, Arnold
