I'm just a bloke doing some stuff, the more interesting bits I post on my blog. Scroll down far enough and you'll see me riding from Melbourne Australia to Birmingham, England in 2014. But now I'm working on another project, a single cylinder motorbike engine at 2750cc!
Here’s the final assembly of the sleeve drive crank, sprocket and drive pin. Finally looking like a proper engine component! The three holes in the sprocket are to allow it to be removed, rotated 120° and refitted. With the 44 teeth not being divisible by 3, this provides a finer valve timing adjustment than jumping a whole tooth.
Until the patterns arrive that’s all of the machining completed. Time to look at that gearbox and decide whether I can make it work for me.
While I was looking at Faceache on the couch, a good friend of mine Matt was busy with his home made furnace. It took a few goes and a couple of blown elements, but after a few days rough cast part arrived outside the garage.
The mighty KLR650 that took me all round the world had took the hump going up and down the Coventry Easterm Bypass. Who could blame it, given the wonders it has seen only to end up in such a miserable shithole. In winter. 😦
Anyway, the linkage under the swinging arm had seized solid. I had to cut it out and it cracked as a result. Mr. Kawasaki wants £160 for a new one. Plus £140 for a set of needle roller bearings. Plus £48 for a new spindle. And Mr. Uk Taxman wants his 20% VAT.
In an attempt to see what I can do for free with the tat lying around, Matt offered to have a go at casting a new one using the original as a pattern. This was an excellent start! His persistence paid off while I was still sat on the couch. Now known as the casting couch 😉
Here’s the final sleeve drive assembly, complete with chain tensioner in situ. The distance between centres is as drawn, with the adjuster fully in to give the full travel as the chain wears. Shown in the orientation it will take in the engine on final assembly.
It looks right and with the 9 holes (3 sets of vernier adjustment) we can get to within a single degree of timing. Spot on!
The valve timing needs some thought still as the Hercules was supercharged, so the inlet opens late. Static timing can be set with the drive sprockets, however, the relative timing between inlet and exhaust can only be changed by re-shaping the holes in the sleeve. I only have one sleeve so that’s a one way operation.
How much is too much? You will only find that out after you’ve done it and there’s no going back. Hmmm..
So my trusty bench is going to become a test bench, for real! Nick asked whether the new gearbox would fit on the Churchill lathe. His idea is to make the control electronics and troubleshoot now, rather than when it’s all together in the bike frame. Makes sense to me.
However, while it’ll just about fit (the Churchill has a 12" throw) I don’t want to tie up such a useful machine for any length of time. A quick call to Matt and a spare motor was dropped round a few minutes later! Got to love having a good engineering mates community:-)
The motor is flange mounted and happens to rotate the same way that the engine will. So, with a bit if cobbling around I should be able to make a test bench and drive the torque converter (Tc). The first thing I will be able to uncover is the direction the Tc is designed to rotate! I have a sneaking suspicion that it’s the ‘wrong’ way, i.e. opposite to the engine. Time will tell…
The sleeve drive sprockets are machined up and the chain fitted. The distance between centres is critical and the chain length dictates that. The distance we’re chasing is 7 inches, which the chain adjuster helps – but the critical distance unfortunately falls between links.
The engine cases will need to be bored for the bearings, so the centres can be moved to provide a small offset. However, changing the centre of the sleeve drive crank will change (raise in this case) the maximum height of the sleeve. This in turn means that the barrel will need to be raised, lowering the compression ratio.
Important to nail this now before machining the cases. I think a maximum of .1" will bring the chain length, tension and adjustment within acceptable limits.
I picked up a gearbox for the project and now have a whole series of fresh challenges! The Toyota iQ box is a novel CVT, with an ECU ensuring the pulleys extend between four fixed ratios. The effect is like a 4 speed automatic, but achieved without any actual gears.
I could have taken the easy option of using a standard clutch and a brit bike or Harley box. However, if I did that anyone looking would recognize it straight away. The idea is that you look at the engine and wonder what the hell it is, and wherever else you look there are no more clues!
The fluid flywheel (on the other side) means the whole assembly is there, ready to rock. I just have to figure out how to drive it, and knock up some electronics. Easy right?? Hmm…
We’ve petty much finished all of the steel components now, so Bob has been busy mulling over how we’re going to tackle machining the engine cases. While I’ve been reviewing the hand written notes and scratching my head!
It does make sense and doesn’t seem too onerous either. I just hope the patterns don’t take too long, as they’re holding us up.
Looking at transmission and after a good catchup with an old friend I’ve decided to go fully automatic. Modern small cars with CVT transmission have compact boxes presenting many options. I like the idea of not having a clutch level and cable, it will clean up the bars nicely.
Setup for measuring the runout on the drive side. Currently out by 20 Thou, but not fully pressed home yet. Once I’ve located a large press and finished squeezing them together, the operation can be repeated and the wheels trued.
In many Brit bike factories the truing up process was done by dropping one end of the flywheel assembly onto wooden blocks. The momentum of the other flywheel would tweak it round slightly. This weighs over 50kgs so we’re having a re-think on that one!
The end of the timing side needs a shoulder putting on it due to a design change. (Clearance for the sleeve drive chain links). In order to do this the crank assembly needs to be mounted and spun, which was quite a challenge! The conrod doesn’t clear the lathe bed so it’s been suspended from the ceiling with a bungee, to allow it to move but retain some tension. It’s a full sized turning crank that gives a good idea of what’s going on inside the motor, not something you see every day!!
When the crank has been finally pressed together, we’ll need to check the run out. Ideally this will be zero, but is something that must be checked if longevity is going to be achieved! (And I do plan on the engine lasting!).
Minor runout could be adjusted with subtle use of a mallet, or for anything more serious machining one shaft. Or even making an eccentric sleeve. But hopefully none of these will be required.
The idea of the v blocks is to mount the whole crank assembly in the bearings on the timing side. The lot can be spun by the conrod and a clock on the other side measures any runout. Easy!