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.

[JasonBModerator @jasonb]

The valves were quite easy to make, being a length of 3/16″ stainless steel threaded both ends. The valve head was screwed on with some Loctite while still a basic cylinder and once set the seat was cut at 45deg. I did the two valve seats while the topslide was set to that angle. These had to be tapered on their OD and bonded in with JBWeld as there was no way the suggested push fit would have worked with the way the holes were done.

The kit makes use of a Stuart Governor kit  which was mostly there. The one piece that was missing was the largest casting which is the butterfly valve body. I used the CNC to cut a new one on the end of some bronze bar, I deviated from the Stuart design which has a separate pipe flange and included an integral boss for a screwed connection. As I’m not going to be using rigid copper to plumb this up there is no need for a separate flange and it looks neater.

The two other cast brackets for the arm pivot and in the case f the Jowit a pair of jockey wheels to guide the belt needed a bit of encouragement to accommodate the drawing dimensions that was easily done with a hide hammer. The holes were added and then the casting rounded off so the outside was concentric with the holes. I’m using a small 35mm vice in the photo to support the overhanging boss for drilling and reaming.

It must be close to 40yrs since I last built a Stuart governor, this one seemed to go quite easily and I have a better equipped workshop now. Not being a fan of bling I made the L shaped arms from steel rather than the usual brass that Stuarts supply. I also reduced the size of the supplied 2BA locknuts down to 4BA hex and reduced the hight too.

I think that is about all I took photos of which took me to a stage where the engine could be test run. Very happy with how slow it will go considering it is single acting, slowest at the end of the vid. Some final fettling, stud making and paint to follow.

 

[Michael GilliganParticipant @michaelgilligan61133]

Lovely job, Jason

The terms “Silk purse” and Sow’s ear” come to mind !

You evidently can.

MichaelG.

[JasonBModerator @jasonb]

Thanks Michael, the purse is now finished

As the other two had been painted in Ford Highland Green there was only one option for this engine.

Continuing the minimal bling theam I went with satin black for the governor brackets rather than polishing up the gunmetal

I did splash out on a bit of red for the cylinder cover, would have been nicer if this were an iron casting for looks. The letters had a skim cut taken off their tops after painting to bring out the bare metal, left at that no polishing.

That completes the Trilogy

Finally a video of the engine running; the trio are also shown running together at the end.

 

[Simon Williams 3Participant @simonwilliams3]

What a success story.  Well done!  I read the beginning of this thinking “where do you start!”

One question which relates to full size engines as well if I may.  What is the reason many of these engines have a throw on the crank such that the piston shows its skirt out of the cylinder bore each revolution?

As always, many thanks in anticipation of the combined expertise of the forum.

Simon

[Adrian R2Participant @adrianr2]

Can the governor set a running speed on this scale of engine or is it more of a limiter? I’d imagined that the weights would sit at around 45 degrees steady state but does not appear so.

[JasonBModerator @jasonb]

The piston coming out the bore is often said to save a ridge forming at the end of the cylinder which could happen as the piston wears against the cylinder. You also see this on things like crossheads where they travel just beyond the ends of the guides.

Adrian, I wrote this on MEM which should go some way to answering. I might go and have a play with a second hole in the link rod.

The governor does move nice and freely and unlike a lot does not seem to suffer from belt slip. I don’t have excessive stretch on the belt as that all adds drag but I did cut the vee in the pulley at 60deg rather than Stuarts 90deg which should help with grip. The jockey wheels probably help a bit too by giving a decent amount of wrap around and reducing the side rubbing that you get when the belt meets the pulley at an angle.

I think I could possibly have gone a fraction shorter on the link rod but at the speeds and pressures I run at there is too much blow buy due to the open ended butterfly slot to reduce the flow enough to hold it at tickover speeds.  It will speed up if I manually open the governor so does have some effect but I’m not going to be running it at the speeds where the balls are all out.

Plus with no load to vary you don’t really need a governor to hold the engine at one speed, they are just for show. Possibly a No9 would be different as that is a faster running engine and likely to do work where as the beam, victoria, JC, Real, etc are all slow running engines to look at.

[Adrian R2Participant @adrianr2]

Slow running is much nicer to watch. One could decide on a preferred running speed and then tweak the governor spring so that the balls just lift off the stops, or even wind a variable rate one.

[JasonBModerator @jasonb]

I shortened the long horizontal link.

At the start you can see that the governor is holding the speed, when I manually override the governor the engine speeds up then drops back down when I let it run by itself.

The second half shows the engine being loaded by ushing on the flywheel (quite hard) and the engine speed drops. The Governor does what it is really meant to do when the load is taken off by limiting the unloaded speed so the engine does not race away. It is a bit jumpy as the single acting cylinder throws the balls out on the power stroke and there are no dashpots to dampen the action.

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