Jowitt Major Completion

[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 was done 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 porosity 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.

<a href="https://www.youtube.com/watch?v=YlOuUmVWBFI" target="_blank">http://www.youtube.com/watch?v=YlOuUmVWBFI</a>

As you can see in the ebay listing photo the flywheels were the stuart ones with the "lumps" where the spokes joint 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.

[Dave Otto]

I always amazes me how much damage people can do to an engine kit before they get frustrated, quit and stash it away out of sight. Probably more work fixing all the problems than just starting from scratch.
Nice work patching it all up.

Dave

[Chipswitheverything]

Whoever decided that a silk purse cannot be made from a Sow's ear was obviously not any active member of this Forum, where these miracles seem to happen with a fair amount of regularity!  Will be interesting to see this build log, or account, as it progresses.

[Sanjay F]

Amazing transformation and I narrowly avoided this one as I saw it on eBay and well beyond my restorative capabilities!

It’s a big old engine compared to the smaller version, watching along   

[Jasonb]

Dave, as you say starting with a block of Iron may have been the better option given the number of "features" that were hidden within.

Chips, it has turned out to be quite a nice purse

Sanjay, I think you could have done it with some forum guidance. Even if you did not at the price it went for it was not a bad buy. Less than the cost of two new Flywheel castings from Stuart and there was the best part of a whole untouched governor kit in there too.

Yes it's quite a size, you will have to wait for the full trilogy to be revealed


I snipped this image which shows the amount of filler I still had to use on the other side of the casting which was a lot worse than can be seen in my earlier photos.

[Krypto]

Love watching a good fix-up article, although this one is special as the project had never been assembled in the first place!

The lathe/flywheel pic didn't come through for me, although I know I seen it somewhere as it finally moved me off my butt to order the two lathe tools (L&R) to utilize the spare corner of the CCGT 060202 insert.  Not sure why I need them, however, as with the "recycler" face mill that uses these inserts I think I have more blunt-offside inserts than ones with good regular corners.

[Jasonb]

Ops, that was me not copy and pasting it correctly from the Forum where I wrote the post. Should be there now, it's a short video.

[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 towards 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, pedestals 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 pedestals 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.

[Michael S.]

Hi Jason,
That’s an interesting engine. I’ve never seen anything like it. A steam engine with cam-actuated valve gear?
The engine frame is perfect.

Michael

[Jasonb]

There are a lot with eccentrics that operate the valves such as this, quite popular in Germany from what I can see. Also a lot of uniflow type engines have a cam operated poppet valve but as they are usually hidden inside that may be why you have not seen them..

http://www.dampfundmehr.de/start_dateien/verbund_einzyl.htm

I would not say this engine has a true cam as the "cams" are just eccentric round discs so there is a gap between disc and valve rod when the valve is closed and they only come into contact for part of the revolution which is when they are open. I'm sure it would work with more conventional lobe shaped cams which would be particularly good on the exhaust side as they would open and close quickly allowing the used steam out easily.

That reminds me I deviated from the drawing and doubled the exhaust passage area which was originally shown as the same as the inlet, this should help with slow running as less flywheel energy on the non power stroke will be used to push the air out a small restrictive hole.

[Michael S.]

I am already familiar with these valve-controlled steam engines; they come in many variations. The engine shown on the homepage is indeed one of those types, featuring valves and eccentric discs.
What I haven't seen yet is the cam disc that actuates the piston valve—similar to an internal combustion engine.
I like this variation.

[Charles Lamont]

Cam operated valves are quite common on steam engines.

Trevithick & Vivian's patent of 1802 shows cams.

Cams were use to operate double-beat drop valves (or Cornish valves) on beam engines, eg the engines at Claymills.

There is an engine by Wills at Westonzoyland Pumping Station that has a sliding 3-dimensional cam controlled by the governor to alter the cut-off.

There were several cam operated valve gears for locomotives, including Lentz and Caprotti.

Sentinel steam lorries (and locomotives) had poppet valves very much like those on an IC engine, again operated by sliding camshafts, but with (typically) three discrete cams for different cut-off in forward gear. 

[Jasonb]

I have also used it with a piston valve, but the follower is in contact with the cam for the whole of the rotation.

I suppose it would also be possible to use it with a conventional slide valve if the follower were set to constantly be in contact with the cam as it would act just like an eccentric with a spring to keep the rod and cam in contact rather than an eccentric strap.

<a href="https://www.youtube.com/watch?v=9C77uVWmB0k" target="_blank">http://www.youtube.com/watch?v=9C77uVWmB0k</a>

[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.

<a href="https://www.youtube.com/watch?v=bBqextCdtgg" target="_blank">http://www.youtube.com/watch?v=bBqextCdtgg</a>

[crueby]

Runs quite well, looks great!  I love how the governor came out too!