What were the lyrics of the Aussie songwriter John Williamson's hit: "Every Australian boy needs a shed"? My shed has been host to the V twin steam engine project below! Enjoy. (Please be patient as numerous photos are loaded).
Plans and ideas have to start somewhere. I think that's as close as I got to drafting it. Although for later drawings and revisions I used CorelDRAW to create the vector designs.
I took more care with the crankshaft drawings.
Cast iron bores and blank pistons still joined.
Crank, big-ends, bores, pistons. Crankshaft components ready for assembly
The trickiest part of this job was to discover the stresses in the crankshaft after welding. Thus the crankshaft needed re-machining. Next time I'll simply try to press fit them together. It's too hard to try to offset machine the entire crankshaft from a solid piece of steel.
Crankcase block being assembled, held with clamps prior to being welded.
(Is alloy casting any easier?)
Block with crankshaft and bearings fitted.
CorelDRAW is excellent for vector drawings. Beats hand sketches anyday!
Handmade conrods. Small end bearings made from brass water tap handle.
Test fit and alignment of bore bases and conrods
Block now fully welded, drilled and tapped.
Angle view prior to fitting the heads.
The head was machined from an odd length of railing someone once gave me.
Making progress with the heads, gringing the outer flange shape by hand. (Aesthetic reasons only). Inlet/exhaust port still to be drilled.
Test assembly of parts, now including partially machined heads.
Drilling the steam ports for the rotary valve in the heads. This is where I could have done with a mill. Very hard to get perfect given that the drill press was working to its limit.
Now for the eccentrics. Some 35 years ago Sid Higgs who lived near the Western Tiers in Tasmania showed me a small V twin steam engine he had made. What fasicated me were the eccentrics. The sketches above ensured I properly understood the timing.
Eccentrics now with lifter rods fitted.
Progress so far.
Machining the rotary valve.
Continuing work on head, with bronze bearing now in place, rotary valve machined to fit, and brass retainer - to hold rotary valve in place.
Further fine tuning of eccentrics, with the small guide helping to limit any sideways movement of the eccentrics.
Drilling 3.2mm alignment hole through eccentrics into front of crankshaft. I used broken high speed drill bit for the alignment pin.
Finally, the linkages from the eccentrics to the rotary valvue. This was rather a "trial and error" effort as the first linkage was "slightly out". I also here machined all the bolts/pins, but the dome nuts came from the hardware store. Notice that the throw from the eccentric to the rotary valve is ampified to give almost a 45 degree turn.
Top view of eccentrics and linkages to rotary valves. Note also some aesthetic work on the linkage holding plate, while also making the crank visible for oiling purposes.
Welcome 2011. Daughter Jessica took this photo. I set the engine out in daylight so I could better see the alignment of the rotary valves - and manually hand file them into alignment.
The engine as it currently is. I tested it out with compressed air, and the throw of the engine is there but not sufficient without a flywheel. (Now to also work on the plumbing - copper piping to the heads).
Turning the flywheel.
At this point I have completely disassembled the engine. There were several reasons for this. Getting ready to cut a keyway in the crankshaft as well as the flywheel. And, I also wanted to re-drill the eccentrics alignment pin.
Milling the keyway in the crankshaft.
Steam engine reassembled, ready for a test run using compressed air.
We've used the steam engine now on two occasions at market stalls. And overall it has attracted quite a lot of comment, discussion and memories.
I've now decided to remake the heads - to improve steam-flow with a larger ported rotary valve. The two-part heads will be braized together.
We used this steam engine in a recent film, thinking through the merits of the creativity, design and engineering required to get it working. In other words, it didn't develop unaided - it required a designer an engineer. Sounds like the antithesis of what our kids are asked to believe in science class.
The head components are now braized together.
Further tweaks, including more accurately machining of studs,
and heat dissipation fins on the cast iron sleeves.
At this stage we've decided not to use rings, but in order to retain oil longer in the bores,
I've machined four grooves in each piston.
Close-up view of new head and bore assembly.
Now I was hoping for the engine to run faster with all these tweaks, but the new heads with bigger porting still doesn't make much difference. In fact, intially the engine was rather "sluggish", but this was due more to the eccentrics mechanism binding at one spot. I think the next stage will be to enlarge the inlet port, as well as increase the size of the copper inlet pipes. But that's a job for another day.
Finally decided to make new, larger inlet piping, using a pipe bender, and silver soldered the conjunction together.
Detail of new steam intake piping.
Top view of steam engine. We increased the steam/air pressure this afternoon, and are quite pleased with the increased speed.
On our third and probably fastest test, one of the eccentrics pushrods broke at its weakest point. The pushrods have been strengthened by braizing the previously threaded joint - but it looks like we'll have to re-manufacture the eccentrics mechanism to heavier specifications.
The steam engine as it currently is, April 2011.
The short film clip above is of the steam engine being test run using compressed air. Several features became apparent while testing and we'll share these challenges with you as we take this engine development further.
After discussing the pros and cons, I've decided to make a new crankshaft with the big-ends at a 90 degree offset. This is prompted by the reality that this is a V twin, and needs to run at low revs. The original 180 degree offset of the big end bushes doesn't allow for perfect piston timing. The 90 degree offset will allow a better throw and distribution of "push".
We've approached the making of the new crankshaft in a completely different way. No welding or braizing. We've press-fitted the individual components together with Loctite. We've devoted these photos to this rebuild because it was perhaps the most challenging to get just right. Even after press-fitting the components, the front main bearing shaft was "out", which required careful removing, re-machining a new section before finally successfully pressing it in.
The crankshaft also features internal oiling ducts, fed in via the front retaining bolt.
A closer view of the the oiling ducts on each of the big-end pins. Notice the plugged hole at the end of the pin.
We've also made new bronze big end/pin end bearings for the conrods. The big end pin is smaller at 20mm allowing for a thicker bearing shell - which was easier to machine.
Brass sump, silver soldered together, functioning as a dust guard as well as a sump for excess oil. Self oiling mechanism is the next step in the development of this steam engine.
View showing flywheel and recently added steam exhaust pipe.
Will update with further photos and information as I progress. Many thanks to Martin of Whittakers Engineering in Northam for his helpful advice and suggestions.