Author Topic: Hick Crank Overhead engine  (Read 8963 times)

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #45 on: December 12, 2020, 05:05:24 PM »
I promised about a week ago that I would attach photographs of the Portface block and Valve chest. These are attached.

The studs are loose in the castings. They will be Loctited on final assembly. I tried locking them in place using shellac varnish with the idea that they would be easy to unlock (either by heat or soaking in methylated spirits). This did not really work. While the idea was sensible it was messy and took a long time to “cure”.

I have now returned to making the little fiddly bits.

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #46 on: January 21, 2021, 12:50:18 PM »
This is not really a progress report, more of a celebration.

Very little work has been done since my last posting. I spent the days before Christmas wrecking a corner of the workshop to provide space for the new lathe. After that the cold has only allowed me to use the place three times. I am still making fiddly little pieces about which I will report in a few weeks time.

In one of my early blogs on this engine I mentioned my concern about cutting 3/64” wide slots. After advice and postings on this forum I found a firm in Surrey that supply a vast range of cutters mainly to industry. I bought three HSS slot cutters over the internet and they arrived next day. Yesterday I cut my first 3/64” slot, 3/16” long through 1/16” thick mild steel. And I did not break the cutter.

 :) :) :wine1:

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #47 on: July 06, 2021, 05:46:27 PM »
I have not posted a progress report for quite some time. For the early part of the year my workshop life has been dominated by the cold weather and having to build a bench for my new lathe. I got back to the model by Easter after the new lathe was installed and continued to make small and complicated items.

Early May I returned to the Cylinder to bore it out to ϕ3/4”. Back in October I reported that a casting defect could be seen after the Cylinder had been bored out to ϕ5/8”. The Cylinder was once again set up in the Keats plate and bored out to ϕ3/4”. On inspection the casting defect had become a 1/8” blow hole with some evidence that it almost reached the outside surface (see attached photographs). Thinking, I decided I had the following options:
1.   Nothing. It is only a model and should still look pretty when finished. It may not work at all and the piston ring, if an O ring or graphited string, would be destroyed if run.
2.   Try filling with epoxy resin or soft solder. Access is difficult particularly for cleaning before and after filling the defect.
3.   Sleeve the bore. The sleeve would have to be thin, about 0.040” thick, and prevented from rotating (shrink fit?).
4.   Drill through the wall at the defect and silver solder in a bronze plug. Sounds radical but I think this would have been the best option before final machining.
5.   Get another casting. If one was available there would still be quality concerns.
6.   Machine a new cylinder from bronze bar (or cast iron?). This would take some time machining to shape.
I put these options to a meeting of the local model engineering society where it was suggested to sleeve the bore, doing the final boring with the part machined sleeve in place in the cylinder.

I decided I had enough room to take the bore to ϕ13/16” to take the sleeve. The minimum thickness of metal to the steam passage and tapped holes would be between 1/16” and 3/32”. I bought a reamer for the job and made plug gauges to guide me.  Back to the Keats plate and using a ϕ3/4” bright steel bar I set the cylinder up to run true (I was now getting quite good at this). I bored and reamed the cylinder out to ϕ13/16”. A 4” length of ϕ1” Colphos 90 bar was turned down to 0.004” below ϕ13/16” (a 0,05mm being the optimum for the Loctite used) and bored out to ϕ5/8”. I have always had problems with drills wandering off the drilling line when drilling deep holes in bronze. Someone at the society said he drilled holes in bronze at high speed. I tried it (about 500rpm for a ϕ1/2” hole) and it worked, no problems. After cleaning and using an activator (Loctite 7063) I glued the sleeve into the cylinder using Loctite 638 (high strength retaining compound) and left the assembly to cure for most of a week.

The Cylinder was returned to the Keats plate and the assembly bored out to ϕ11/16” (just over). I felt that I should not push my luck by going “the whole hog” to ϕ3/4”. The surface finish was good and the bore parallel so a reamer was not used for the final cut (I have found that a new reamer in bronze scores the bore and I did not fancy sitting down and stoning the rakes off the end of a reamer). The bore was honed using a wooden laps and x600 grit (the finest I have). Finally the steam passages were re-drilled.

I now have a good cylinder. I am rather impressed with the Loctite.

I have not included the usual progress photograph since the model is dismantled.

I have made the piston, piston rod and cylinder cover. These will be the subject of my next report (soon, I promise).

AVTUR
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Offline Admiral_dk

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Re: Hick Crank Overhead engine
« Reply #48 on: July 06, 2021, 07:55:38 PM »
Good news that you got it saved and can continue with the build  :cheers:

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #49 on: July 18, 2021, 05:27:59 PM »
Very early on in the model build I had a think about the Piston Rod. It is about 5 1/2” long with a step from ϕ3/16” to ϕ5/32” about half way along. Although I have done it I do not like turning down long lengths of small diameter rod so I sought an alternative way to produce the piston rod. I decided to do a trial at silver soldering two rods together. Holding the larger rod in a collet chuck I drilled a hole up the centre, about 0.008” larger than the diameter of the small rod for about 1/2”. Flux, as a dry powder, and small chips of solder were loaded into the hole and capped by the small rod. A fire brick was placed on each rod and heat applied. Even with the bricks the rods had to be carefully pushed together. It worked remarkably well.

A year later I decided to finish the rod only to find I had used ϕ5mm and ϕ4mm rod. The process was successfully repeated with ϕ3/16” to ϕ5/32”mild steel rod. The result was not quite straight and proved very difficult to correct using a simple three point bender. I did the best I could and decided it did not matter. Looking at it a couple of months later, when finished, I think I did pretty well.

The ends of the rod were simple to finish but a 3/64” wide slot was required in the ϕ3/16”rod just above the join. This locates the Crosshead (which will be described in the next report) using a cotter pin and pad. The crosshead, part made, had a long body with a 6BA hole away from the slots to clamp the rod using a brass screw. A similar arrangement using a square bar was used to keep the alignment after the crosshead was removed. Prior to cutting the slot the crosshead was assembled on to the rod and clamped. The second bar was also clamped, square to the intended slot on the larger diameter part of the rod. Two ϕ1,1mm holes were drilled with great care across the crosshead and rod. The cross head was removed, the rod returned to the milling machine and the slot cut between the holes. The ends of the slot were filed square (sort off) with a needle file.

The cylinder cover and gland were made without problem. The cover was a casting with a spigot which was only there to hold it during the early machining operations. I have one comment on my machining; I tend to keep to tight tolerances which leads to some filing when fitting. The Piston was made from good cast iron and presented no problems. The final turning of its outside diameter was done on the piston rod held in the collet chuck. The clearance is about 0.004”.

I was concerned about the lack of room to fit the cylinder cover screws. The four of them would be too long to be fitted head down between the two flanges. After some thought I decide to make studs of the correct length, Loctite the top nut in the correct place and pretend that the nut below the flange was the screw head. On doing the trial I found that could fit the screws with the correct length (lucky the holes were slightly over size).

More to come. I am beginning to think that the end is in sight so what am I going to build next? I fancy designing my own engine (I have started designing engines in the past only to find they were getting too complex).

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #50 on: November 27, 2021, 04:00:56 PM »
It is over four months since I posted an update. This one covers the crosshead and connecting rod.

The Crosshead was started months ago as part of a silver soldering session. About 1 1/2” long length of mild steel 3/8” square bar was cross-drilled towards one end and a similar length of ϕ3/16” mild steel bar silver soldered in place. The piston end face was faced and the rod hole was drilled and reamed. The square bar was turned to a diameter for about 1/16” from the face and the hole well chamfered, at 45°, to butt on the shoulder of the piston rod. After the cross drilling of the crosshead and the Piston Rod, in situ, the rod was removed and the slot for the cotter pin and pad finished. The part was mounted in the four jaw chuck and the trunnions machined. The dead end with the tapped hole to take the clamping screw (described previously) was cut off and the part glued to a short length of ϕ5/32 mild steel rod. The top, crank end, of the crosshead was then carefully faced to length. The rod was then removed by a sharp, light, tap with a hammer and the crosshead re-glued to turn the final chamfer.

I did a lot of thinking about how to make the Connecting Rod which is forked and looks very flexible (I attach the drawing of the part). Prior to starting I solid modelled a number of machining options.

Two ϕ10mm holes were drilled at the ends of a 4” length of 1 3/4” x 3/8” mild steel plate for bolting the plate directly on to the milling machine table. In addition two ϕ3mm datum holes were drilled so that the part could be quickly re-positioned after being moved. With the plate sitting on a similar aluminium plate the “top” surfaces of the connecting rod were machined with a slot drill. The rod was the removed and the aluminium plate machined to give a mirror surface so that rod had a good base to sit upon. The rod was turned over, sat on the aluminium plate and the “bottom” machined in the similar manner.

ϕ3mm holes were drilled at every internal corner and at the ends of cutter runs. Prior to cutting the part out with a ϕ3mm slot drill end holes for the cotter pin and pad slots (two 3/64” wide and one 1/16” wide) were drilled. These slots were then cut to just over half depth followed by the edges, again to just over half depth. The part was turned over and the slots and edges cut through. I now had successfully produced the rod without breaking any small drills. Because it was thin and forked I decided it could easily be damaged. Therefore, before any further work, two small brass blocks were glued in the fork (these have been removed a number of times, just rest a long face on a flat metal block and give the brass a sharp tap). An attachment shows the connecting rod after tidying using a selection of small files.

The progress on the model is way ahead of this blog. Since the weather is too cold for the workshop the next posting could be quite soon.

AVTUR
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Offline Jo

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Re: Hick Crank Overhead engine
« Reply #51 on: November 27, 2021, 04:37:23 PM »
Well done. You have made a good job of that connecting rod  8)

Jo
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Offline Admiral_dk

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Re: Hick Crank Overhead engine
« Reply #52 on: November 27, 2021, 08:05:12 PM »
That is a rather complex shape for 'a simple conrod'  :o - but very nice result, that you can be happy about  :cheers:

Per

Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #53 on: November 28, 2021, 12:05:46 PM »
That is a rather complex shape for 'a simple conrod'  :o - but very nice result, that you can be happy about  :cheers:

Per

Per

Everything about the engine is complex.

AVTUR
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #54 on: December 22, 2021, 02:59:25 PM »
Autumn has come and gone. During that time I have been occupied making and trying to fit small fiddly bits.

The connecting rod has two little end bushes (Geoffery King calls them brasses, a name I have not seen before and not quite in my Collins English Dictionary) and a single big end bush. Each is held in place by a strap with a cotter pin and pad.

The straps were produced from rectangular bar with the outside dimensions matching the width and thickness of the strap. I cut the bar to a length far longer than required for one strap and the drill the ends of the eventual slot to easy slot cutter access and to locate to filing buttons. The buttons were used to facilitate the shaping of the end with a file. The two small straps have rounded end while the large, big end, strap includes a boss for an oil hole. I did not make too much of a mess of this filing exercise. After the slot that holds the bush was cut the slots in the sides for the cotter pin and pad were produce using a slot cutter cutting from pre-drilled holes. The cotter slots on the small straps are 3/64” wide while those on the larger strap are a 1/16”. The ends were filed squarish with a modified needle file. I discovered that I could buy a 1mm across the faces file that only cut on the edge. I bought two knowing that one edge would have to be ground back to get into the slot. In the end I also had the grind back one of the faces. The surplus end of the part was then removed with care using a slitting saw. And I have yet to break a 3/64” slot drill.

I have made cotter pins and pads before. Then there were ten sets required so I cut a length of rectangular bar on the milling machine with the head set at a slight angle to give the correct profile and then sliced the bar like bacon using a slitting saw. While this worked the control of the cotter angle was poor and I felt I could do better. A short strip of 1/2” plate had the profile of the seat of the pad cut in one end and the other left square. Slots were then cut with a slitting saw on both ends so the remaining strips of metal were the correct thickness, 3/64” and 1/16”, for the cotters. The plate was transferred to a vertical slide set at 7° mounted on the lathe cross slide and the pins and pads cut off with a slitting saw. Sharp edges were then removed with a small file.

The production of the 3/64” thick cotter pin and pad for the crosshead was included in this work. Geoffery King only used a pin in his design but I opted for a pin and pad.

I have more photographs covering the making of the cotters and bushes than allowed for a single posting. Therefore details for the bushes will follow shortly.

AVTUR
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Online Kim

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Re: Hick Crank Overhead engine
« Reply #55 on: December 22, 2021, 03:21:28 PM »
Neat! That's a pretty ingenious way to make the slope on the cotter pins.  I like that!
Kim

Offline Jo

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Re: Hick Crank Overhead engine
« Reply #56 on: December 22, 2021, 04:27:51 PM »
That looks good  :) ... I hope the red stuff on it is not blood  :paranoia:

I also call that type of bearings Brasses.


Jo

P.S  If you need to cut a thinner slot than you feel safe doing with a slot drill type milling cutter I found using a thin wood rough cutter from either side and joining with a needle file worked  ;)
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Offline AVTUR

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Re: Hick Crank Overhead engine
« Reply #57 on: December 22, 2021, 04:38:50 PM »
That looks good  :) ... I hope the red stuff on it is not blood  :paranoia:

I also call that type of bearings Brasses.


Jo

P.S  If you need to cut a thinner slot than you feel safe doing with a slot drill type milling cutter I found using a thin wood rough cutter from either side and joining with a needle file worked  ;)
With my present skills I am happy to try to cut narrower slots with a slot drill, until I start breaking cutters. I treat such items as disposables.

I will explain the "blood" in the next posting.

AVTUR
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Offline propforward

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Re: Hick Crank Overhead engine
« Reply #58 on: December 23, 2021, 01:36:38 AM »
It’s a fascinating build - I really enjoyed reading it. Some trials along the way but the engine looks marvellous.
Stuart

Forging ahead regardless.

Offline steam guy willy

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Re: Hick Crank Overhead engine
« Reply #59 on: December 23, 2021, 01:59:00 AM »
Looking good and I see the drawings are in fractional Inches.  I think they were used before digital  became popular and was approached by using sharp pointed dividers with a deeply etched steel rule.! I do have a modern digital veneer that has fractions as well as metric and imperial scales ??!

Willy