Author Topic: Hick Crank Overhead engine  (Read 8962 times)

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #30 on: December 18, 2019, 07:48:53 PM »
It has been some time since I reported my progress on the model. Cold weather forced me out of the workshop and other persons set my priorities. However I have made some progress.

The Caps for the Plummer Blocks are gunmetal castings, or to be more correct, one casting. This immediately leads to a question: Should I use the casting and try to copy it when machining the second cap or should I make two identical caps and ignore the casting? Thinking I would not be able to produce a good copy the casting I chose the latter option. Two simple caps were made from round bronze bar, what type of bronze I do not know but it was not aluminium bronze. I think I will put slopes on them, like the casting, when it is warmer.

The bearing Brasses were made from bronze bar. The usual way to make these is to solder pairs of partially machined blocks together just as Andy (Chipmaster) on his Stuart Major Beam Engine. My attempts to do this in the past have failed completely, I even considered silver soldering. Thinking about it I decided using a fixture to hold the two halves together was the answer particularly when there are a lot of brasses to make. Before going ahead with the first fixture I had a chat with a former work colleague who makes large model locomotives and such like. He sort of laughed: “As an apprentice, the first day on the shop floor I had to machine and match large bearing brasses. We did not use solder, a ****** large fixture instead.” I made a nice set of fixtures (photograph of one attached) and job became easy – just mount the two halves of the brass in the fixture, put fixture in a lathe collet chuck, drill and ream the bore, face the front face, turn the clamping plate round and face the rear face.

I sat down and started drawing out such a fixture but, since the Brasses were about twice the size of any I had made before, it was quite large – too large to take advantage of a collet chuck. Also was it worth making a fancy fixture for just two sets of Brasses? Previously I had a stupid idea of using the Plummer Block and Cap as the fixture and doing the machining in the milling machine. This had the obvious advantage that the Brasses would match the Blocks and the Caps. I re-visited the idea and decided that if the structure was supported by a plate to take the vertical machining loads while a machine vice clamped everything together it was not stupid. It was also very simple.

During the preparation of the Brasses prior to facing, drilling/reaming and matching I hit a problem – I just could not understand drawing and wasted a day trying to do so. I sat there not understanding what Geoffrey King had drawn and dimensioned. It was a mess unlike his drawings for the smaller sets of brasses. It was nothing like the drawing I would have produced. I then realised that a dimension was missing – problem solved. I puzzled over the mistake and decided he was trying to draw too many parts on one sheet of paper. This seems to be a common failing in model engineering. I was trained to draw one part, however small or large, on one or more sheets of paper with plenty of room. The drawing started with three or more views using the favoured projection. Then additional views, sections, dimensions, notes etc would be added without crowding the drawing. Rant over.

A simple support plate with a hole in it to give a passage for the drills and reamer was made. With the assembly clamped and tapped down on to the plate, and having taken lots of measurements to ensure the bearing hole would be in the centre and of the split of the Brasses, the bearing was drilled, reamed and faced. The drilling was done with increasing diameter steps prior to being machine reamed with an H7 reamer to hopefully give a bore between 0.3125” and 0.3129”. The assembly was turned over, re-clamped and the reverse face faced. Before the assembly was taken apart for marking the entrances to the bore were well chamfered.

After the excitement of the bearings, the Crankshaft (I would call it the main shaft) was easy. The bearing surfaces were done first. A parting off tool was used for the rough machining which was followed up with a freshly sharpened left hand knife for the final cuts. The top slide was set at an angle of 2.5° to facilitate very fine cuts. The shaft was turned round in the collet chuck to cut the surfaces in the reverse direction. The journal adjacent to the crank has an axial float of about 0.002” and a diameter of about 0.3122” (a bit tight, a bit more polishing required). The flywheel journal has an intended generous axial float and a diameter of about 0.3110” (a bit free running, the brasses may need to be closed very slightly). The nose which carries the Crank is a good push fit. The keyways for the Crank and Flywheel have been machined. For good reasons I have not provided a flat for the governor bevel gear grub screw.

I have just started on the Flywheel (diameter 7.5”). An update will follow in a few days.

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #31 on: December 30, 2019, 08:01:13 PM »
The Flywheel has been machined and now, or more likely in a few months time, needs finishing with a file. There were no problems but it took a little time, I don’t really like machining cast iron. I had hoped to machine the faces with the wheel in my big four jaw chuck before finishing the rim using the face plate but everything was too large for the lathe gap. Therefore everything was done using the faceplate. I recessed the rim of the wheel which Geoffrey King left as an option. As far as I could see there were three ways doing this:
1.   Mount the wheel on a rotary table and milling out the recesses, one face then remount the wheel to do the other face, with slot cutter – this sort of made sense.
2.   Keep the wheel on the faceplate and drive a square faced tool, like a parting off tool, square in to the face. This is rather like trepanning which I have done on brass plate. I consider this much more frightening than parting off.
3.   Keeping the wheel on the face plate and cutting into the face at an angle of about 20° to the surface with a knife tool, to a depth of about 0.015”. The cut is the opened out using the lathe cross feed, and so on. This takes time and requires left and right hand knife tools but is much easier and gentler than the other methods. I have the time.

I broached the keyway. I had not done such work before and I knew it would be difficult. I ground the end of a short length of square high speed steel to what I thought was a sensible shape and mounted it in a quick change tool holder. By manually advancing the carriage I found I could shave off around 0.001” each in each pass. It took quite some effort, both hands, and however tight I did the nut up the tool post eventually rotated requiring the tool to be reset. I managed to cut a slot 1/32” deep. I feel that this job was at the margin of the lathe’s ability. Both my hands suffered but the arthritis in my left wrist seems to be less now. If I had to broach a number of keyways I think I would make a lever system as shown in Ian Bradley’s book Myford Series 7 Manual.

After all that I made the associated key by filing.

I am now going on to make some of the small governor and control items. Quite a few are fiddly and need to be thought about. So it is going to be a few days producing planning sheets.

The more I think about the Standards the more I believe that they are not fit for purpose. Whether this is my fault I do not know. However I have bought some 5/8” aluminium plate with the idea of machining a pair.

AVTUR

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Offline MJM460

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Re: Hick Crank Overhead engine
« Reply #32 on: December 30, 2019, 08:49:00 PM »
Hi Avtur,

Coming along pretty well.  It is always good to see another update.

I do like that detailing on the flywheel.

What is the problem with the standards?

MJM460

The more I learn, the more I find that I still have to learn!

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #33 on: January 04, 2020, 06:52:22 PM »
Earlier this week I wrote that I was not happy with the Standards. After doing the running trial assembly with the finished crankshaft and bearings I found that the shaft is about 5° to the model centre line. In other words the top of one standard is out by about 0.22”. Not very clever and all my fault.

The two options are:
1.   To try to correct the existing standards. This, I feel, is trying “to make a silk purse out of a sow’s ear”.
2.   Or to make a new set which will take some time but is quite achievable.
In both cases a lot of thought is required.

I do not intend to rush in to this work. I am still writing job sheets for the small parts between migrations to the workshop. I have discovered I need more metal but I do have enough Φ3/32” mild steel rod to make 12BA nuts and bolts!

AVTUR

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Offline Jasonb

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Re: Hick Crank Overhead engine
« Reply #34 on: January 04, 2020, 07:24:45 PM »
You could try some over size holes in the bottoms of the bearing pedestals which may just give you enough movement to swing them into line. Bit more involved would be to solder plugs into a frame sand pedestals then redrill and tap, if you tak ethis option then best to drill it as an assembly rather than individual parts, I did similar with the Allman A frames.


Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #35 on: February 19, 2020, 08:49:36 PM »
I have not posted a progress report for some time. This does not mean I have not been busy. When it has been warm enough I have been in the workshop making governor parts. Most of these are half finished, in most cases waiting for a calm day so that I can silver solder and harden silver steel outdoors. When it has been cold I have been producing lots of planning sheets (wasting a lot of paper and ink).

Making the six (actually seven because I made a spare pair) 12BA Nuts and Bolts was fun! The governor assembly nuts and bolt heads are cylindrical, diameter 3/32”, with a set of flats, 5/64” across the flats, and are mild steel. I started with two sets of taps and dies expecting to break at least one tap. I did a trial manufacture of one bolt without difficulty but ran into a problem with the nut. I just could not drill the hole up the rod for tapping. In the end I used a length of 3/16” diameter bar which was turned down after drilling and tapping. The parting off was done using a cutting disc in a Dremel mounted on the cross slide of the lathe. I had used this arrangement for parting off square headed screws and nuts in the past. I started on the bolts only to have a bolt break off in the die [see the thread I posted last month under “Mistakes, muckups, and dangerous behaviour”]. Still, I had a new second die only to find it had a broken tooth. After ordering two replacement dies I sat down and had a think: Everything would be easier if I cut the heads off 12BA screws, of which I had quite a few, make a second set of nuts and glue them together to make the screws. This was done, using 222 Loctite (I don’t think Loctite grades mean very much with very small screws) and filing the tops flat. The spanner flats were filed using a small piece of hardened gauge plate with a 12BA clearance hole as a stop. The bolts will be filed to length after a trail assembly of the governor. Happy, except that one, the spare, nut has gone walkabout. Now I have to make two nut runners.

Geoffrey King’s drive to the governor spindle was through two bevel gears, the pinion on the crankshaft had 20 teeth and the wheel on the spindle 24. The overall diameter of the pinion was 0.643”. I have only cut simple cycloid clock gears. Small bevel gears are a completely different matter. Looking at various books (Ivan Law’s “Gears and Gear Cutting” and “Gears for Small Mechanisms” by W.O.Davis) it seems that making a good set of bevel gears is possible without hobbing but the whole method/result appeared to me to be a bodge. Anyway I decided that the gears I required were too small for me to make. Fortunately a set of gears, about the right size, were included in the kit. However they
1.   were the same size, a ratio of 1:1 compared with 5:6. This was considered acceptable
2.   had a bore of 3/16”. The diameters of the crankshaft and spindle are 3/8” and 3/32” respectively
3.   The boss diameter was 7/16”, far too close to the crankshaft diameter.
A quick look at the catalogue of a leading supplier showed that bevel gears are expensive and I was unlikely to find a set with a ratio of 5:6. So the supplied gears had to be modified.
1.   A plug would be silver soldered into the bore of the wheel, the plug drilled and reamed to suit the spindle and the dead end of the bore faced to length. The required hole for the 10BA grub screw would be drilled and tapped with a short counter bore to locate the screw during assembly.
2.   A sleeve would be silver soldered over the existing pinion boss to bring its diameter up Geoffrey King’s of 9/16”. Again the boss faced to length and the bore drill out and reamed to suit the crankshaft. Geoffrey King used a key to locate the pinion, however I opted for a grub screw.

I have to admit I was worried that silver soldering might mess-up the gears. Prior to any silver soldering I calculate the amount of solder required for the joint and add on about 25% for the fillets. The solder is then placed so that it finds its own way into the joint during heating. Finally I add a little extra using the rod of solder. I used typewriter correction fluid to keep the solder away from the teeth etc, vulnerable areas received three coats. After running out of Tippex I found that the local supermarket sold Snopake (who buys such stuff these days?) which gave a far thicker coating. I managed to do the soldering, along with some hardening, on what seems to have been the only calm day this year. I was pleasantly surprised with the results. The gears have been finished except for one solder fillet which I will admire for some time before tidying up.

The one other finished part is the Governor Sleeve that did not give any problems. One thing it taught me was that a lot of the small parts can be made from one end of a bar/rod which allows one to have a good holding spigot.

I have started looking at the alternative Standards, more about that later.

AVTUR
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Offline MJM460

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Re: Hick Crank Overhead engine
« Reply #36 on: February 19, 2020, 10:24:56 PM »
Hi Avtur, good to see another update.  Those small parts do take a lot of time to make.

MJM460
The more I learn, the more I find that I still have to learn!

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #37 on: April 08, 2020, 01:20:21 PM »
Things have been a little slow on the engine but now that warmer weather has arrived and I am having to discipline my life things might be quicker. The lack of calmed days, I use the propane torch outside, delayed silver soldering and hardening of filing buttons. Whenever a good day arrived it always clashed with a social event.

I have completed the governor parts. The drilling of the Balls and the machining of the fancy 12BA Nuts and Bolts and the Sleeve has already been reported.
 
The Governor Arms required a couple of fixtures to hold them during thinning. I started with 1/8” square mild steel bar over 3” long for each arm. Most of the length was lost during the thinning. First one end was threaded, 10BA, for a short distance, holding the bar in a big four jaw chuck on the lathe. The bar was then thinned to a width of 3/32”, equally on opposite sides (first fixture) and then, likewise, to a thickness of 3/64” (second fixture).  Keeping the arm in the fixture, the two 12BA clearance holes, one for the arm bracket pivot and the other for the link pivot, were drilled through the arm. I got quite concerned that these holes were off centre on the arm until I realised that they are completely hidden by the bracket and link. The arms were then filed to shape.

The Governor Arm Bracket was produced in a similar manner to the sleeve – machined on one end of rectangular 1/2” x 1/4” bar. First a groove was turned to provide area for a small slot cutter to stop or start and the hole for the drive rod drilled and reamed. Then the pivot holes, 12BA, and grub screw hole, 10BA, were drilled and tapped (not quite true; looking at photographs I realise the 12BA holes were done after the slots were cut). The slots for the arms were cut using a 3/64” slitting saw. I have to admit that I do not like slitting saws for many reasons. They seem to be particularly ill suited for vertical milling machines. I ended up holding the bracket in a small precision vice mounted in a larger vice. It seemed rigid enough and the slots were successfully cut. The cheeks of the bracket were rounded with file and buttons before being machined back taking very light cuts with a slot cutter. The part was parted off from the bar and tidied up with a file and buttons.

The Governor Links were made from one length of 1/4” x 1/8” bar. The pivot holes, 12BA, were drilled and tapped along with a hole that formed the fillet radius in the link. The two parts were separated and cut to length. The ends were slotted using the 3/64” slitting saw and the waists were produced and the arms cut back to the fillet using a 1/8” slot cutter. Finally they were finished by file.

The assembly of the governor proved quite fiddly. The clearances on the sleeve had to be increased to get free movement of the links. Other than that there were no problems except that the 12BA bolts and nuts could not be tightened. A special nut runner will be made. The bolts need to be shortened so that their ends are flush with the nuts when tight. After that the bits need polishing.

I am sorry that I do not have any photographs of the finished links and arms. If anyone wants them I am happy the dismantle the assembly and provide them.

I feel that I am making some progress but I am left wondering how Jo can make a model in two or three months.

AVTUR
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Offline Chipmaster

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Re: Hick Crank Overhead engine
« Reply #38 on: April 08, 2020, 01:42:39 PM »
Governors seem to be in vogue at the moment, well done Avtur.

Andy

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #39 on: May 19, 2020, 06:19:57 PM »
At the turn of the year I reported that I was bitterly disappointed with my work on the Standards and considered starting again using aluminium plate. About a month ago I took a good look at the existing Standards and decided to try to correct them:
1.   I corrected my clumsy milling on the feet of the Front Standard by cutting two small blocks of bronze (probably phosphor-bronze) and soldered them in place using high temperature silver solder (740oC to 800oC).
2.   Four bronze plugs were made and silver soldered into the existing 4BA clearance holes in the feet. Low temperature solder (630oC to 660oC) was used. I had some concerns about this operation since I had already plugged these holes in the Front Standard once using bronze plugs and epoxy resin. However it worked.
3.   The bottom and sides of the plinths were milled to shape. I also took the opportunity to increase the cavity in the plinths to ease access for the 4BA nuts.
4.   Now to drill the 4BA holes in the correct place. The plummer block fixing holes at the top of the Standards were correctly positioned so I decided to mimic the main bearings/crankshaft assembly using a bit of aluminium plate. With holes drilled in right places with a datum the Standards could be bolted to plate with their feet in the air. This assembly was mounted in a vice, correctly aligned, the datum found and a small diameter hole, about 1/16”, drilled for the centre of each 4BA hole. I decided that this arrangement was too weak for the drilling of the clearance holes so these were drilled with the Standard clamped onto an angle plate. The whole operation was a success and everything was aligned correctly except for the rocker spindle bearings.
5.   The existing bearing screws, 8BA, needed to be moved. My idea was to fill the holes with low temperature silver solder, re-machine the faces and drill correctly position holes. This was an immediate failure since the molten solder would not fill the holes. The solder just climbed out and flowed away. With the second standard I dropped a short 10BA brass screw into each hole which allowed the solder to plug the hole. The first standard was then plugged in a similar manner. The silver solder was machine back to give a new face and re-positioned holes drilled and tapped.

I am happy with the results, everything is aligned and free.

I have continued making small parts, so another report should follow soon.

AVTUR
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Offline Admiral_dk

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Re: Hick Crank Overhead engine
« Reply #40 on: May 19, 2020, 09:42:08 PM »
It's always nice when you can modify your work result from something you aren't satisfied with to a nice result  :ThumbsUp:   :cheers:

Per

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #41 on: June 07, 2020, 06:58:30 PM »
I have made the final parts of the engine structure, the Bracket, Angle Piece and other bits that locate the top of the governor spindle. Attached is a drawing of the arrangement which has the bracket bolted to the back of the front standard and an angle piece bolted to the back of the rear standard. These are separated by two distance pieces to allow passage of the pump and valve rods from the eccentric. The bracket carries the governor spindle bush. The correct positioning of the bush is achieved with distance pieces between the bracket, angle piece and standards, all held together with 8BA screws.

Geoffrey King’s drawing of the bracket suggests that it is produced from 1/8” thick mild steel plate bent to shape. This is beyond my workshop capability unless I resorted to blacksmithing (more about that in a later blog). My options were either to machine it from solid or fabricate it from three small pieces of 3mm thick plate (I did not have 1/8” plate!). The second option was used. Roughly shaped parts were loosely pinned together with 10BA screws and silver soldered. Milling machine and files were then used to finish. A 1/4” hole for the bush was drilled and reamed. The bush, phosphor-bronze, was made to be a slight interference fit in the bracket.

Obviously the angle piece was to be made from 3/8” x 1/16” thick mild steel angle. I do not have any and a quick search of the usual model engineering metal suppliers suggested they did not either. I dismissed the idea of making it by bending 16 gauge sheet because the finished result might look out of place. So it was back to silver soldering, making it from 1/16” thick strip and a little piece of 3mm plate.

With these changes Geoffrey King’s lengths for the distance pieces were meaningless. These were determined by trial assemblies of the standards bracket parts, the governor and a base jig. The jig replicated the bedplate with the footstep bearing. The adjustments were for the bracket. The spindle passing though the bracket bush had to align with the footstep bearing, cleanly and being able to spin. The bracket needed some aggressive adjustments prior to making the front standard distance pieces. These were made long, the difference in length between the two pieces being important. The rear standard distance pieces were made so that the adjacent hole is the bracket and angle piece lined up. Finally the bridging distance pieces between the bracket and angle piece were made. The back of the rear standard had to be cut back to allow access to the bridge stud nuts (Geoffrey King does point this out in the drawings). Finally the standard distance pieces were shortened by the same the amount to lower the assembly. The aim was to have the spindle bevel gear coming out of mesh when it was sitting on the bracket bush. It would then be put back into mesh by adjusting the spindle collar against the footstep bearing. I hope that all this makes sense.

The work on the brackets went hand in hand with getting the crankshaft aligned. First I had to reduce the front journal diameter get the shaft to run free when assembled in the brasses and plummer blocks. Then it would not rotate when bolted to the engine assembly. Line reaming the brasses made no improvement. In the end I slotted the plummer block fixing holes just as Geoffrey King had done. With the bits assembled including the flywheel the crankshaft and governor spindle train spins easily. The above distance piece and crankshaft work took between 15 and 20 hours

The next stage is to make the eccentric bits and finish the valve mechanism bits. As recorded I have been doing trial assemblies as the model progresses. This has made me realise that the final assembly will be complicated and difficult. There appears to be only one assembly sequence and access to small nuts and hexagonal headed screws is fiddly. So far I have been using cheese head screws in the trials in the belief that they are easier to handle. I need to start a first attempt at assembly instructions soon.

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #42 on: July 13, 2020, 01:08:06 PM »
I have completed the first half of the valve mechanism. The arrangement is different, to say the least. The eccentric, on the crankshaft, is conventional but its strap is held by the water pump plunger, not the valve rod. The motion to the valve is transmitted through a number of links and a rocker shaft. There is nothing like a Stephenson’s motion, the engine ran in one direction and if there was a variable cut-off it is not modelled. The engine can be stopped by disengaging the Valve rod, hanging from the eccentric strap, from the rest of the mechanism by using the Gab handle [see attached annotated picture].

The Eccentric strap was made before the Eccentric. There was nothing difficult or unusual about making it. I did worry that the bore, as cast, was large and may give problems when the strap was bored out after it was split. Likewise the Eccentric was easy with the crossing out taking most of the time. I only use metals of known providence, I do not raid scrap yards or scrap bins, and try my best not to mixing my stock. I chose a nice, short piece of mild steel bar for the eccentric and started to turn it. It cut beautifully with a very fine finish, far better than ordinary mild steel. I then realised I had bought about 6 inches of EN24T bar with a similar diameter to make a short crankshaft for an IC engine many years ago. I guess that the off-cut was put in the mild steel box.

The Short and Long rockers were fabricated, round bar for the boss and rectangular strip for the arm. The Short rocker was made in October as a trial which worked. The bar was drilled from both ends, a shallow hole to act as a datum for milling operations and a deep hole over half the length of the bar. A slot was cut to half the diameter of the bar, into the long hole, for the arm. The long hole was stuffed with short bits of silver solder and flux and heated. The Long rocker was made in a similar manner but the soldering was done after turning the handle and thinning the arm. The end of the handle was turned with a little form tool. A hole that matched the handle diameter was drill in a small piece of gauge plate and the surplus metal removed using a hacksaw leaving a nice little inside radius. The plate was hardened and tempered and the top surface ground to give a cutting edge. It worked. The strip, square, was clamped to a simple fixture, just a trough cut in a small piece of aluminium plate, and thinned using a slot cutter. No comment is needed about the Stud carried by the Long rocker.

Making the Valve rod was simple with the shafted being thinned to 3/32” by 1/8” from 1/4” square strip in the same way as the Long rocker.

The Gab end handle was produced in the same way as the Long rocker handle. It was then bent by heating to red heat, slipping a tube over the handle while holding it in pliers. By the time it came to bending, about three seconds after removing the flame, it was no longer red hot. However it worked and looks neat enough. The rest of the work was milling, drilling and filing. However I did manage to break a 3/32” slot cutter when cutting the slot for the Stud which meant a lot of delicate filing of the slot to get it to fit snugly.

As drawn the Pump rod was rectangular strip, 3/32” x 5/32”, nearly 5” long with additional 8BA threads at each end. I did not have enough 3/32” thick strip and, quickly looking on the internet, nobody could sell me any. I thought about using 5/32” diameter rod but chose to try to follow Geoffery King. I managed to thin down 7” of 1/8” x 1/4” strip to 3/32” x 3/16” and decided that would do. The resulting strip was nicely bowed (one side now not having any residual stress). The bow was quickly removed using a 4” vice and four 1/4” BSF bolts that had shanks (not threaded up to the bolt end) as a four point bender. The underside of the bolt heads were super-glue to the top of the vice faces so that the two central bolts were about 2 1/2” apart. The straightening operation worked like a dream taking less than two minutes compared with fifteen setting up and over sixty thinking about it. There is a just perceivable bend in the other plane which I have left. The lathe with a nice big four jaw chuck was used to produce the 8BA ends.

The next job is the cylinder. I have had a long hard think about the machining operations and will start in about a week’s time. Before then I must clear-up the workshop. It has become a tip with too much kitchen and motorcycle junk.

I have a possible question: Sometime soon I must consider the fixings (nuts and bolts). Like Geoffery King I will use hexagonal headed bolts/screws. He seems to have made his own but I have bought them off the shelf and will shorten them, as required, using a lantern chuck. He did not use washers. Looking at drawings and pictures of Hick & Hargreaves of the period they certainly used washers. It is my intention to fit a washer under any nut that does not lock the thread.

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #43 on: October 10, 2020, 05:22:40 PM »
It has been three months since I last written a progress report. I have managed to get all the kitchen junk and most of the motorcycle spares out of the workshop. I took a lot of workshop rubbish to the local tip (re-cycling centre). I even made a bat box. Also I sold the Kawasaki.

I took a long hard look at the Cylinder casting and realised that none of the major casting faces should be used as datums. Obviously the final datum is the centre line of the cylinder bore which has to be square to the Bedplate. The valve face should be parallel to the centre line and midway between the front Standard. It follows that the most important face is the underside of the mounting flange (Face D in the first attachment). However this can only be machined with the cylinder rotating horizontally on a mandrel between a rotary table and centre. Therefore the casting had to be prepared for drilling with an under size bore to take the mandrel.

First Faces I & J and Edges A & B were filed clean and square so that the valve face, Face G, could be machined smooth BUT not back to the final dimension. When mounted in the machine vice there was a considerable slope on the face which was fly cut (a tool I don’t really like) flat. The casting then clamped to the lathe cross slide and the ends skimmed with the fly cutter so that they were square to Faces G, E & F. The optimum position on each end for the bore centre line was then marked out using a surface table and very nice second hand height gauge. The casting was put back on the cross slide and height set using an alignment microscope in the headstock spindle. A ϕ7/16” hole was drilled part way up the cylinder from its bottom, dead, end (Face H). This was repeated with a smaller hole from the top end to meet the existing hole (I have a mistrust of drilling long holes in bronze). Once happy I drilled to the depth of the bore, 2 1/2” with a ϕ1/2” drill.

Feeling pleased with myself I made a between centres boring bar and tried taking the bore out to ϕ5/8” Complete failure, the tool would not cut and the bar was far too flexible. At this point I did look at a Keats plate but in times of desperation one reaches for the big four jaw chuck. Taking great care with mounting the cylinder in the chuck I managed to reach ϕ5/8”. I also managed to bore all the way through the cylinder, a really sensible mistake (and I mean it).

A stepped mandrel was machined from a ϕ1” steel bar (see attachment) with a ϕ5/8” section that was location/clearance fit with the bore. A 3/8”BSF nut forced the cylinder tight against the step. This was mounted between the rotary table and centre on the milling machine table. Edges A & B and Faces E & F and I & J were machined to size. The circular edges of the flanges and cylinder body were milled every 10° to gives surfaces that were later filed smooth. The mounting flange faces and the underside of the cover flange were then machined. The latter is important since the gap between the flanges has to be large enough for the fitting of the cover screws.

The assembly was then held vertically in the machine vice and the underside of the mounting flange spotted, using a ϕ4mm x 100mm centre drill, prior to drilling the holes for the Bedplate studs. The holes were then drilled using a similar long drill. I discovered that I had drilled 6BA clearance holes instead of 8BA holes. A lot of thinking, in the end I decided to use 8BA studs each with a ϕ2,8mm collar (more about that later).

The cylinder was removed from the mandrel. A bronze stepped sleeve was turned up and silver soldered in place at the bottom of the cylinder. The hole was then tapped to 1/2” x 26t.p.i. (Whit) to give a nice boss. One mistake rectified. It was then returned to the four jaw chuck and the top of the cover flange, Face C, faced back to give the required flange thickness.

The face for the valve portface block, Face G, was milled back to the correct distance to centre line and the two steam passages were cut. Great care was taken with the six 8BA tapped holes for the portface block screws since they end very close to the cylinder wall. This scared me so I left the bore at ϕ5/8” in case of problems. Luckily there were none and I can take to bore out further, to a maximum of ϕ3/4”. Fortunate since there is a small defect (blow hole?) on the surface of the bore.

Finally the four bolt holes and the two stud holes were drilled for the cover bolts. The bolts and studs are 10BA and I inadvertently drilled the stud holes for tapping at 10BA clearance. Fortunately there is sufficient metal present to tap them to 8BA and use stepped studs.

During this work I found two errors on Geoffery King’s drawing:
1.   The radius of the mounting flange is given as 3/8” when it should be 3/4”. Obvious.
2.   The distance between the top two sets of tapped holes for the portface block screws is given as 1 5/8” when it is 1 3/8” on the block. This could give you trouble.

The final boring and lapping will be done some time in the future.

I finished this work over a month ago and have make studs, quite a few studs, and the machined the bodies of the valve since. This will be written up next time it rains.

AVTUR
There is no such thing as a stupid question.

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #44 on: November 30, 2020, 02:46:58 PM »
Since my last report it has rained but remained warm. Therefore I have been working away in my poorly heated workshop and not reporting on my work. I am now making full use of a cold spell to catch up on non-workshop work.

The Portface block and Valve chest are cast iron castings which makes a change from gunmetal (or whatever you like to call bronze). In both cases the iron machined easily, there were no hard spots or holes and the skin presented no problems. There was excess iron on the Valve chest where the mould had collapsed slightly. This worried me until I started to machine it.

The Portface block overcomes the problem of the steam passages between the valve face and cylinder. The outer ports connect with passage slots cut in the side face of the cylinder that transfer the steam to either end of the cylinder. The exhaust steam from the centre port passes through two slots to the exhaust manifold. The Portface block is attached to the cylinder by six short 8BA countersunk screws until the final assemble when it will be glued in place in addition to the screws. I have no idea what glue Geoffery King would have used in 1956. (K N Harris in “Model Stationary and Marine Steam Engines” suggests a mixture of litharge and glycerine. Litharge is lead monoxide, not easy to obtain I guess). I will use a thin film of good epoxy resin.

The Portface block casting required quite a bit of machining on the two major faces to bring it to drawing dimensions The only thing I messed up on was the steam inlet ports, I misread the drawing (Geoffery King’s drawing practise would not have been acceptable at the apprentice training school) and drilled a ϕ1/16” hole centred on the outside edge of each port instead of the centre. The hole was to give relief for the ϕ1/16” slot cutter used. Fortunately the holes were drilled at the end of an afternoon shift and the mistake discovered next day. After a quick think I filled the ports with J B Weld, drilled the relief holes at the ends of the slots, the correct positions. I then did a lot more thinking, drawing and doing sums only to find that Geoffery King had been very generous with valve lap, even with my little mistake the valve shoe closed the inlet passages for quite some distance either side of the end travel. The slots were cut from both sides since their length was 11/32”. I have not bothered to square the ends since the engine will never be required to deliver a lot of power. One or two of the holes for the fixing screws just broke into the exhaust slot side wall. This is of no concern since the block will be glued in place. The only other difficulty I had was countersinking the top screw holes, I needed a ϕ3/16” diameter countersink. Fortunately there are companies out there that will supply one by post within 24 hours.

The Valve chest presented no real problems. The casting flash was removed with ease using an end mill. The cavity was cut out using a slot cutter followed by an end mill to square the corners at the steam inlet end. The two corners between three sides remained a bit of a mess but they do not interfere with the valve shoe.
There was no casting for the Valve chest cover so it was machined from a short length of ϕ1 3/8” cast iron (Meehanite?) bar without any problems. Likewise the Gland was produced from phosphor-bronze bar.

Up until now I had been using any available cheesed head screws for ongoing trial assemblies so I took the opportunity to make studs from steel BA screws (of which I seem to have plenty). The ends were cut to length as I had done with the 12BA screws [The screw was held, locked in place with a nut, in a short length of tapped brass bar mounted in the lathe using a collet chuck. It was then parted of using a small abrasive disk in a Dremel mounted in the tools post (attached is a photograph I have shown earlier)] and the cut end chamfered. However simple this sounds it took time particularly with 8 and 10BA screws (if one drops on the floor don’t bother looking for it). While writing about studs, six sleeved studs 8BA were made for the cylinder mounding flange. A short length of ϕ1/8” steel rod was tapped with an 8BA thread and cut in to 1/16” lengths. Again the Dremel was used in the lathe. One each was loctited to an 8BA screw and turned to the required diameter. The stud was then produced from the screw as above.

As mentioned earlier I have been doing trial assemblies as the model progresses. The cylinder and valve assembly was more than a tight fit in the bedplate and between the standard feet so quite a bit of filing had to be done.

I have yet to photograph the finished valve chest parts and the assembly with the cylinder. These will follow soon.

AVTUR
There is no such thing as a stupid question.