Jowitt Major Completion

[JasonBModerator @jasonb]

I was originally asked about machining the flywheels  (did not fit owners lathe) and tidying up the rough casting pretending to be the cylinder. I won’t go into details but I have ended up taking the engine right through to completion and although I did not take that many photos will describe some of what wa sdone here.

From the original ebay listing it looks as though the partially machined set of castings and materials have been maturing for some time. Along the way a few bits have been lost, the main one being the cast engine bed along with a couple of governor parts. The plastic box of steel stock did not make it to me either, not a bad thing incase that rust bug is catching!

 

The cylinder casting was quite rough with a lot of shrinkage at the sides and it looked like a previous owner had milled some flats to enable it to be held while boring. The bore wa snot bad but there were a lot of pits either from porocity or maybe there was not enough machining allowance to get a clean bore but as it was going to be run for display I left the bore alone.

As I got further into the build I found that the long 3/16″ holes for the two piston rods had wandered all over the place, the counterbores for the valve seats were not concentric to the valve holes, tapered, oversize and the wrong depth. The supplied oil pots did not fit the tapped holes and the stud holes to hold the cylinder to the bed were again all over the place.

Having established that the bottom of the casting was reasonably parallel to the bore I set it up and took a skim off the top of the cylinder so that I could accurately hold it upside down for further work. I don’t often use the 100mm ARC vice as it is too big mounted conventionally but was ideal for this when mounted along the mill table,

The width of the bottom could then be brought to final size and the undersides of the two wings tidied up

I then treated the casting much like the solid blocks that I used to make my smaller versions out of and shaped the outside with a series of cuts. I ended up taking 2.5mm depth of at the ends but still had to resort to using some JB Weld to fill the very low areas.

The facets were then blended with a file to get a nice series of flowing curves. I also added some shallow counterbores so that bosses could be bonded in around the oiler positions.

The endcaps were very tarnished and hard to tell they were gun metal and not rusty iron. The builder had also used the tip of a pointed tool to mark the position of the bolt PCDs rather deeply so a skim cut over all those parts brightened things up. I also turned the spring retainers and cams.

 

The turning of the flywheels was quite straight forward after a quick bit of fettling with files. I like to get the hand work out the way first as there is less risk of marking the freshly machined surfaces. The spare corner of a CCGT 060202 insert and about 300rpm soon had the turning done.

As you can see in the ebay listing photo the flywheels were the stuart ones with the “lumps” where the spokes join the rim which I personally do not like so these were milled away on the rotary table followed by some Dremel work to blend the machined surfaces into the cast ones.

Well that covers what I was originally supposed to be doing, the next few posts will cover the rest.

 

[JasonBModerator @jasonb]

I had looked into various options for the missing bed casting as the owner had also asked me about that, options ranged from getting a family member to 3D print, using Craftcloud to 3D print in a reinforced filament as well as an Aluminium print together with a fabrication much like I had used on the smaller versions I built earlier. With the decision now being mine I went with a fabrication.

The side plates were shaped on the manual mill as the two curved cutouts were regular arcs so easily done with a boring head, holes for cap head screws added and then I tilted my vice so that a face mill could be used to add some draft angle to get the cast look.

The two end plates were drilled and tapped for M4 screws and I milled a pocket in the bottoms to accept a smaller offcut of the 12mm aluminium for the feet. The two plates were held back to back which kept the setup simple, full depth 12mm cuts.

Once the four main parts were screwed together with some JB Weld in the joints I clamped the base to an angle plate mounted on the lathe’s cross slide to cut the draft angle on the ends.

A bit of car body filler in the screw holes and to form fillets in the internal corners, rounded the external corners with a file and it does not look too bad.

Jumping back a bit in the order of work the piston and conrod were not too bad so all I did to them was add a grub screw up from the open end of the piston to lock the gudgeon pin in place so that it could not move sideways and score the bore.

The CI rings had been fitted to the piston but when I went to try the piston in the bore I could not get it in, turns out the rings had not been gapped so would never have gone into the bore. I gapped then to 2 thou but have actually left them out as the engine is only likely to be run for display and no rings makes for a smoother slow running speed.

The crankshaft was a good fit on the big end and straight. However each side was a different diameter and both were tapering in towatds the middle. As the pedestals with their integral bearings had been machined they obviously were a bit slack by the time they had been slid down the shaft. I did not really want to make a whole new crank, pedestalls and bearings so did the best I could. Which was cutting off excess crankshaft length and making the flywheel bores as tight as possible which seems to have worked as I can’t see any wobble.

The faces of the bearing were rubbed down on some Emery to close the bearings up a bit. I also found that the machined bottoms of the pedestals were convex so they rocked, easily fixed by taking a skim off the bottom which also made them the same height which they were not when I got them! Holes were drilled and tapped for oil pots which I made to match the three which were included for the cylinder.

It should come as no surprise that the 4 stud holes to hold the cylinder to the bed were all off both where they started and even more where they had wandered to. Same for the pedestalls which were not spaced equally. I ended up clamping my new bed to the mill table and adjusting the parts until the crank turned freely before using a drill to spot all the hole positions.

That was not totally successful, as although the holes entered the base in the right place it was impossible to lower the cylinder down over the studs so the holes in the cylinder needed to be opened up.

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