The Upshur Vertical Single 4 stroke engine with 3/4" bore x 7/8" stroke. Air cooled, overhead valve with wet sump lubrication.
With a successful conclusion to the building of ‘Debbie’, Jan Ridders Simple Two Stroke, the choice of the next project wasn’t too difficult. It had to be a four stroke complete with cams and valves. Once again I am just hoping I haven’t bitten off more than I can chew. Still as Bogs says ‘If you don’t try it, you will never know if you can do it’.
With ambition running way ahead of ability I had ordered a set of plans three years ago from the daughter of the designer Dick Upshur who sadly passed away in 2006. These plans are still available from Helen Whitcher for $20 plus $3 postage. The build of this engine was the subject of a series of articles which appeared in the Strictly I.C. magazine – issues 63,64,65 & 66.
Having already made a start on the crankcase, which is fabricated from six plates to form a box like structure, I came across a series of excellent posts on HMEM from Dave of Kent which included an alternative method of machining the crankcase out of the solid. Apart from a more robust construction it also neatly avoids the tricky to fabricate and securely position cam gear cover which can be seen on the side of the crankcase. As this is a wet sump engine the problem of keeping the crankcase oiltight is no longer an issue apart from a good seal on the back plate of course.
Rather than construct the crankcase from six plates I opted to follow the lead of Dave from Kent who machined his from the solid.
A number of fixing screws were put into place to hold the cover in place in preparation for drilling holes for the crankshaft and camshaft.
Having bored out the aperture for the cylinder liner work started on hollowing out the crancase interior
A honeycomb of chain drilling to remove some of the bulk of the crankcase interior.
A slot drill was brought into play to clear out the crankcase cavitiy. The depth of cut controlled by the vertical stop on the mill.
The crankshaft bore was opened out with a boring tool on the lathe to take a ball race bearing. I was not happy with the use of a boring bar on the mill.
Bearing race was a press fit into the crankcase cover after machining bearing seat in the 4 jaw chuck.
Crankcase and cover now fitted with roller bearings in place of the plain bearings specified on Dick Upshur’s plans.
Crank and cam shafts are tried for free parallel running before proceeding to the next stage.
Having satisfied myself on good parallel running of crankshaft and camshaft my attention turned to sorting out the crankcase innards. First on the list was the conrod – a couple of hours work I thought, two days later I had it knocked into shape, not perfect but deemed ‘fit for purpose’.
Roller bearings were added to Dick Upshur’s original design and here crank and camshafts are tested for free running before progressing to the next stage.
The conrod blank was milled to shape on the milling machine with care taken to accurately position bearing centres which will be bored to size at a later stage.
To turn the shoulders on both sides of the big end a simple jig was made up. OK so it took longer to make the jig than turn the shoulders but worth the effort.
Careful set up of the conrod on the rotary table was achieved with the aid of a centre finder. Time spent on set up will pay dividends.
Machining the small end of the conrod on the rotary table taking care to avoid climb milling which could rip the work off the table.
The conrod – hard to believe this represents two days work ! Phosphor bronze bearings added for improved durability and end cap may aid assembly into the modified crankcase.
Not trusting the accuracy of my lathe turning skills I chose to go for a fabricated crankshaft where I felt I had some chance of success.
Brass counterweight cheeks were turned up on the lathe. I broke a tap forming the thread on one so silver soldered it in place and used a dummy cap screw to maintain symmetry.
Apart from the removal of the centre section of the shaft the crank is now completed, again a great feeling of satisfaction and relief.
Bearing shells were split using a small diamond disc cutter to match split conrod essential for fitting into the machined up crankcase.
With the crank and conrod installed in the crankcase and rotating freely I feel another milestone has been achieved.
With the steel liner installed in the aluminium round, work can now commence on turning the cylinder fins. The four jaw chuck was used due to its larger capacity.
The fins were cut using a Glanze parting tool as that gave me the distance between fins that I was after.
A sigh of relief after cutting the last fin, next parting off to give me the cylinder base that will bolt down onto the crankcase.
Using a bolt circle calculator (you’ll find a free one on the internet) I used the co-ordinates on my X and Y DRO to position each of the six holes.
Using both a roll over cutter and a ball end cutter curves were added to the cam box cover.
With the cylinder sitting on top of the crankcase the Upshur is beginning to look something like.
One of the joys of model engineering is that you don’t normally have to spend a fortune on materials. If some machining operation goes belly up you can always chuck it in the scrap box and have another go without it breaking the bank. However when you have to modify an expensive bought in part you can’t afford to adopt quite the same cavalier attitude.
This was the case for the spur gears purchased from a supplier in Australia which transmit the drive from the crankshaft to the camshaft of the Upshur engine. It’s vital that these gears mesh true, in other words any wobble could result in poor running. Also when I considered the need to silver solder the stainless steel gears I became distinctly apprehensive and was more than happy to entrust the job to Bogs.
Bogs and I felt that the whole procedure could be of interest so it’s over to Bogs for a step by step account of the work involved.
Remember to see a larger image, click on picture
These are the gears that John sent to me for modification. Both are made of stainless steel and cannot be any thicker than the original thickness, so I can’t put a converter hub on there to get around the problem. So it requires a slightly different method than normal.
Just to keep my mind focused when doing a job like this, I make up a rough layout page showing what I have and what is require
I converted my lathe over to accept Myford chucks (they are much smaller than my normal ones) and duly fitted a four jaw self centring one. I prefer these as they give a much better gripping power over a 3 jaw when handling small parts. Because the gears are stainless, I decided to use stainless for the modification, so I chucked up a piece of 11mm diameter. I then turned a spigot on the end that was 0.002″ (0.05mm) smaller than the hole through the gears, and about 0.010″ (0.25mm) longer than the thickness of the gears.
This shows what it looked like. The reason for being so much smaller than the hole is to allow for clearance for the silver solder (silver BRAZE for our US cousins) to penetrate the joint by capillary action.
The filler piece was then really rough parted off, just leaving a very thin flange to stop it falling through the holes in the gears.
I soon had the two required done.
This next picture shows what some people class as a black magic art, but nothing could be further from the truth. Silver soldering just requires a few basic rules to be adhered to to get good results every time. The parts should be clean, chemically if possible (a wipe over with cellulose thinners), good quality silver solder and flux, plus a little flame technique. I am a real tight a**e when it comes to solder, purely because it is so expensive nowadays. I use only just enough to get the job done. Why use too much and then have to clean it off afterwards? So this picture shows just what I used. For stainless, Tenacity flux is a must. But I use it all the time on everything, mixed up with a tiny amount of water until it becomes a ‘runny’ paste. When it dries up in the mixing tub over time, I just add a bit more water to get it runny again and carry on with it. This batch must have been on the go for well over 18 months.
So, assemble the bits. The ring of solder goes under the flange, flux painted into the hole and around the solder, the slug is then pushed down into the hole.
Just like this. Once the parts reach cherry red, you will easily see the silver solder starting to run. When that happened, still keeping the heat on the part, I pushed down on the flange, just to make sure the slug was right through the hole.
After letting the assembly cool down until things have solidified, it was turned over. As you can see, the flux and solder have penetrated perfectly through the joint. No black magic, poking about or feeding extra solder in. Just the correct amount of everything, and a bit of heat.
After both were given the same heat treatment, they were just cleaned up with a wire brush. Tenacity flux comes off very easily.
Now comes the magic bit. I love using soft jaws, they are about the cheapest method you can get to really lift your accuracy while using a lathe. So here, I have swapped the jaws over in my chuck, locked the jaws down onto a thin bit of bar and have just finished gently boring them out so they are a very close fit to the small gear size. Everything has to be completed on the small gear before boring out again to take the larger gear. Notice the back recess, to allow for the sticky out bits on the soldered up gear.
The gear was bedded into its recess, and very gently faced off until I had a perfectly clean face. This did mean I took a minute amount off the original gear.
Having turned the gear around, the same was done on the other side.
Without touching the gear, using a spotting drill, I put in a nice centre for the drills to follow. By climbing up in size, I eventually ended up at 7.8mm.
Followed up with an 8mm machine reamer, to give the correct size for the shaft it is to be fitted onto.
The same procedure was followed, boring out jaws etc to fit the larger gear, eventually ending up with a 6mm reamed hole. Job done and dusted.
A periodical assembly of parts completed to date helps to ensure that the build is on track, especially important where deviation has been made from the original plan.
Next on my list was fabrication of the camshaft. What appeared a simple little turning job on the lathe turned out to be a two day marathon and then I had to resort to finishing the cams by hand in the vice (or vise if you happen to live t’other side of the pond).
Bogs’ modified gear wheel was positioned on the shaft and secured with a keyway cut with a modified blade from my hand held power jig saw (thicker than your conventional hack saw blade). A 1.5mm pin was inserted into the shaft to serve as a key. Again I must thank Bogs for this neat idea.
Cam followers and guides were turned up and slotted into position. The smaller 30 tooth gear wheel was added to the crankshaft and on assembly I was rewarded with a smooth running ‘bottom end’.
I was not looking forward to the next job on my list – the production and fitting of piston rings. As it turned out my fears were ungrounded. I simply followed the instructions to the letter and all turned out well.
With increasing optimism I took the plunge and ordered the RCEXL ignition unit at a cost of around £50 including a neat two way switch for plug in battery charger and a CM-6 spark plug. I bought mine on line from Apache Aviation and have been very satisfied with both the products and service.
When building an internal combustion engine one of the considerations is where to hide all the electrickery bits. When I built my ‘Debbie’ 2 stroke I even obtained quotes to have something made by a cabinet maker but the cost was prohibitive.I finished up making the base myself but it was a job I didn’t enjoy and the result fell short of my hopes. Now I am building the Upshur vertical single I was faced with the same problem. Browsing around fleabay for inspiration I eventually came across pet caskets – you know, the sort of thing you would buy to preserve the ashes of sadly departed Tiddles the cat. For a modest £10 inc shipping you have a neat wooden plinth. Throw away the lid (or keep it for a steam engine base) and replace with an aluminium plate and you have a perfect base for your latest pride and joy. A search on eBay will reveal all sorts of caskets in varying sizes, finishes and prices suitable for adaption into engine bases.
Remember to see a larger image, click on picture
Keyways handcut in gears using a homemade ‘broach’ ground down from jigsaw blade – thicker than a hacksaw blade.
Keyway and pin, a neat solution to avoid slipping gears that could also be employed for flywheel installations.
Spur gear secured to camshaft using keyway and pin and a dab of Loctite for good measure. The cams are temporarily Loctited into position.
A trial assembly confirmed free running of gears. Split threads for two cylinder bolt holes not ideal but I’m keeping fingers crossed !
Piston rings were made from Meehanite (a high quality cast iron) a delicate operation that was not as difficult as anticipated.
Piston rings sliced off the cylinder with a good supply of spares (oh me of little faith !)
After slitting, the gap was wedged open whilst heat was applied for aprox one minute then left to cool naturally.
Heat treated piston rings safely in place on piston and ready for insertion into cylinder barrel.
A base for my Upshur is a modified pet ashes casket bought on ebay for £12
Fins on the cylinder head were cut with a 2mm slot drill rather than use slitting saws.
Rather than have overhang the engine is raised on spacers to provide clearance for flywheel.
Custom wheels for my pipe bender were turned up in brass to form the 1/4″ copper exhaust pipe.
A neat digital tachometer also serves as an ignition 'on' indicator to preserve battery life.
Whilst work has progressed since my last post (as shown below with my pic/captions) I have encountered a number of problems which will require a certain amount of backtracking and the machining of new parts. These problems serve to illustrate the need for high standards of accuracy in the making of model 4 stroke engines. Those guys building multi cylinder engines have my undying respect.
To all intents and purposes I had finished the engine build and thought I would see some signs of life with a temporary hook up to the vapour carb on my ‘Debbie’ Simple Two Stroke. This was a severe case of over optimism and investigation revealed a number of fundamental faults that will need rectification.
1. Lack of compression due to leaky inlet and exhaust valve seats.
2. Poor alignment of the crankshaft resulting in the destruction of main bearings.
3. Shoulder of big end bearing carrier making contact with the camshaft.
I intend to have a few days break from this project before tackling the above issues so anyone following this build please bear with me.
The Hall sensor for the CDI unit is triggered by the magnet which is set into a slave flywheel.
The main body of the spark plug machined from 8mm hex steel bar.
Finished long reach plug – gap was set to recommended 12 thous. This should have KLG quaking in their boots !
Completed cylinder head but leaky valve seats require some attention.
The shoulders of the crank webs retro chamfered to provide additional clearance of the camshaft.
