Honestly, this will be the last post about this kickstart - it's gone on far too long! To be fair though, making the shaft was probably the most complicated machining job I have ever done and I had no idea what the spring cover looked like - so forgive me three blog posts on this subject.
We are at the end though, the cover has been raised a little bit to reduce the clearance between the distance piece and the gearbox end cover and it's been cleaned up and painted.
Once I got a couple of coats on the spring cover I fitted the spring and gave it another blow over to cover over any damage.
And that's it, fitted and finished.
Apart from greasing it... might need another blog post?
After lots of input from the Ariel community, I now understand how the kickstart spring cover is supposed to work.
There are four parts in play, illustrated by this page from the parts book:
LS254, the kickstart lever. I think I have the right one
LS262, the kickstart bush. This comes all the way out of the end cover up to the end of the shaft, LS253. The bush is 1 3/8" OD
LS263, the distance piece. Andrew H of the AOMCC tells me that this is 1 1/2" OD, so the wall thickness must be something like 1/16".
LS264, the spring cover
The big reveal is that it is the distance sleeve that keeps the spring cover in place, and that it is itself kept in place by the kickstart lever. This means the spring cover, LS264, must fit tightly enough around the bush LS262 to be retained by the 1/16" thickness of the distance piece LS263.
The other thing I've seen is that the top of the spring cover is not flat, but follows a nice radius. The former has been back to the lathe for reshaping:
I've prepared another bit of sheet, by cutting it to size, squaring the ends and removing the paint:
Before we start on that, I found a piece of exhaust pipe the perfect size for the distance piece. I made a wooden former so I could cut it to length in the lathe and form a short radius on the end.
The radius prevents it sliding towards the gearbox quite successfully and it fits rather well behind the kickstart lever.
I formed the spring cover in the same way that I did last time but there was no way it would shrink far enough to get to the required inside diameter for the kickstart bush, so I ended up cutting darts in it and welding them up
There is a bit more work to do, but all the bits fit together. I think the spring cover is too long but I always knew I would have to trim it and I need to finish the welding. Lastly there will be a hole for the spring to pass through.
Before we get into that though - this is my latest invention for welding - an arm rest! Makes controlling the torch so much easier:
The arm rest made finishing those tiny welds much less stressful. The welds were backed with a curved copper strip which as I have shown before minimises the dressing required on the back side and gives you much more control when welding this thin material. It's been welded, ground out inside, straightened, ground outside and so on...
Next job is to drill a 1/4" hole near the edge, and file it oval:
Then I've used a drill to form the material such that the spring can pass through:
The spring is wound in from above:
In the video, the spring cover has been trimmed to length and fitted:
It's not perfect but it's nearly there. I shall raise the edge of the cover a little more since the whole assembly has to account for end float in the kickstart shaft, and there is a bit more clearance than I would like.
When you have a few old bikes, and you use them, and especially if other people use them, you must expect a few diversions from your ongoing project whilst you fix the other bikes in the fleet. The Square Four has absorbed a bit of time recently and it's now become the daily rider again while the hunt must have takes a little holiday in Norwich.
Therefore, the Model A has taken a bit of a back seat but it's time finally for the next job. This is the tin cover for a kickstart spring.
To start the job off, we can measure the machined register that it fits on the kickstart cover and then we can work out how long it needs to be by measuring the spring.
I'm going to fold the cover up from a strip of 0.9 mm thick steel around a wooden former which I will turn on the lathe from a chunk of sapele, part of an old door.
I've screwed and glued this former to a suitable piece of timber such that I can hold it in the vise
Here's the first try, cut from a bit of sheet with the aviation snips to a suitable width and rough length. With it held in place on the former some tie wraps, I can mark the end and trim.
We'll do a little trial fit on the job:
We need to bear in mind that this cover is supposed to turn with the spring. The spring fits nicely inside it but I suspect it's rather tight on the gearbox end cover.
The only way to find out to tack it together. A couple of tacks show that it fits nicely will turn on the register on the gearbox end cover, so I fully weld it and dress it on the linisher.
The next step is to work out how long it needs to be. I believe that I will need to fold it over such that the inner diameter just fits the kickstart shaft bush.
A little session with the Wiss snips sees it cut to approximately the right length.
Attempting to spin the end over on the lathe was an abject failure - the wooden former just flew out of the chuck so I returned to doing it with a hammer.
That worked reasonably well, and it fits:
There's something fundamentally wrong though:
With a lot of help from the AOMCC, I've learned that LS263 holds LS264 in place and is itself held by the kickstart lever.
Well, yesterday it was finished. The cotter pin went in way too far and would need replacing, but it worked. However, there was an itch...
I suppose I am a bit obsessive, but I couldn't put up with having to remake the cotter because I had machined the shaft wrongly. I filled the slot up with weld.
A few minutes later, I had re-machined the slot; the shaft is 3/4" within the kickstart lever and the slot has a maximum depth of 0.150" - the easiest way to measure this accurately is from the bottom of the cotter slot to the opposite side of the 0.75" diameter, so you measure 0.600". The slot is bang on the correct depth, and the 0.375" cotter pin fits perfectly.
All I need to do now is cut the spare length off the cotter pin and radius the end, like this:
Now it's finished. Definitely. Apart from the spring cover...
The last step in the long story of the kickstart shaft project is to machine the flat for the lever cotter pin. We are back on the lathe with the vertical slide and will use this setup to machine the slot:
The cotter pin is about 3/8 diameter so we will use this 3/8 end mill to cut the slot.
This is the last pass of 3/8 end mill - and it's a pass I wish I hadn't made. I was very near the end and used a trial fit to find that the slot I was milling was about 1/32" too shallow. For some reason I decided that it would need another full turn of the lead screw to finish the cut - completely forgetting that the lead screw pitch is 1/16". So now that slot is too deep.
I could weld this up and re-machine it, but the cotter pin still fits and stays in place properly. I guess I will leave this until it becomes a problem - I can't get a 3/8" bolt in there, which would be possible if the slot was any deeper.
With the kickstart shaft nearly finished, we need to think about the bush for the lay shaft. This fits in a bore in the end of the kickstart shaft:
The bush will be a top hat shape to accommodate the end of the layshaft and to determine the end float of the low gear pinion. It's going to be made from this piece of SAE660 bronze:
First job is to reduce the diameter to nominally 1” to pass into the shaft with a few thousandths clearance:
Next, we reduce the diameter such that we have a few thousandths interference fit in the 7/8" bore, and add a small chamfer to aid assembly. That done, we can bore it in steps up to 5/8" - our shaft is 11/16", but we will do that last bore in situ.
Parting off the bush. The hang out here is not ideal at all, and I believe I may have knocked the stock out of square in the chuck - it would have been far better to do this job with the revolving steady.
No matter though, this does not affect the working diameters and we can face off the end of the bush if necessary.
The top hat bush, mostly finished aside from the layshaft bore.
It's not as tight as I would have liked, so I have fitted it with Loctite 603 retainer. This won't be cured until tomorrow.
This is the last job for the lay shaft bush - it's been fixed in place and the Loctite has cured overnight so it is now being bored to 0.6875" for the layshaft. Notice that the shaft is in the fixed steady - it is essential that the shaft is bored concentric to the kickstart bush in the outer gearbox cover:
Some while back I had left a little excess material on the major diameter of the shaft thinking that I might need to play with the first gear pinion end float, and so it proved. As machined the shaft is a little overlength and I used this setup to remove around 0.020" from the end of the shaft which provided the necessary clearance.
I'm pleased to say that assembly and testing of the gearbox proved that everything works as expected. The next step, and final step, is to machine the recess for the kickstart lever cotter pin.
Back home after a few days away fitting a new front door and frame at my daughter's house in Kent, I find a few minutes to move the kickstart shaft project along a little bit.
When I left a few days ago I had the shaft set up in the pillar drill just waiting for final adjustment and the fitting of a centre drill to start the hole for the pawl.
That done, we move on to the 9/32" hole on the outside of the shaft. I have discovered that the pin is retained in place by the low gear pinion and cannot come out in service. I bought a pair of long series drills for this job and it makes it a little easier to set the work up on the pillar drill. We go right the way through both sides with this one:
We follow the 9/32" with a 5/16" drill which only goes through the inside web. I'm pleased that the pin fits very well in these two holes and with a little fettling (the pawl was rather ragged) the pawl goes in as well.
I'm a bit concerned by the shape of the pawl where it engages the pinion as the surface, perhaps not surprisingly, is rather worn. A further problem is that the cam which pushes the pawl back into place actually jams the shaft. This is due to the lack of wear in the new shaft I think since dimensionally it is identical to the old one.
Working on the pawl a little to square it up and refine the edges sorts out the problem and we have a pawl that goes nicely into the retracted position:
The video shows it working in both positions:
A dose of heat and a pot of case hardening compound will give us a pawl that fits and has sharp edges giving it plenty of life. We'll have to see if it still works with the bush in place - that might require a bit more fettling, so we will leave the case hardening until that is done.
As we get towards the end of the kickstart shaft project, it's time to think about where the lever will sit and where the flat for the cotter needs to be machined. This picture mocks up what it will look like eventually:
The key to success here is to understand the relationship between the mating face of the cotter and the flat on the shaft, all of which combine to determine the position of the lever. The last thing we want to do is to have the lever too vertical or too low in relation to the rest of the machine - worst still that it sits forward of the gearbox!
We'll use the old shaft to understand this relationship.
What you see here is two pictures of the lever, the cotter and the old shaft. I have used a Sharpie to show the relationship between the shaft and the lever.
We can see that the cotter fits in either direction without affecting the relationship between the shaft and the lever.
This next rather blurred picture - it looks like it's focused on the bench top - shows the Sharpie mark against the flat on the old lever and confirms that the flat is perpendicular to the axis of the lever.
We can use this information when we machine the flat on the new shaft. We'll have a look at some of the reference pictures and get a feel for where the lever should be.
While we wait for the long series drills with which we can finally fit the kickstart pawl, we can look at preparing to drill out for the layshaft bush and for the relief drilling that will clear the layshaft first gear pinion. I need to do some measuring to ensure I understand the various dimensions that will be required, but I know that the bore to clear the pinion will be in the region of 1" diameter.
You will recall that in a previous post we machined off the flange that had been used to hold the shaft in the rotary table, reducing it until it would pass through the fixed steady. We see it in use in the picture below during setup:
The short 5 mm hole that has been used for the revolving centre is opened out progressively until we run out of twist drills. This is the 10 mm drill passing right through and into the body of the shaft:
And here it is opened out to 7/8", which is the largest drill I possess - it actually has an MT2 taper and fits directly in the tailstock:
The next job is to part off the stub, but sometimes it is easier to rethink your approach to a job. I set the lathe up to part off this stub after I moved the fixed steady to the 1 1/8" section, but actually I realised it would be much easier to saw it off:
That took less time than setting up. The orange dust is from the saw blade!
This rudimentary sketch shows us what the dimensions of the hole need to accommodate. As I have no wish to bore the hole to over 1" all the way into the shaft, reducing the wall thickness just where it needs to be strongest, I will make a stepped bush to accept the layshaft and provide a thrust face for the low gear pinion. This will be 1" or thereabouts at the inboard end, and reduce to 7/8" for most of it's length. This will give a thin wall over most of the length of the bush since the shaft is about 11/16".
That's the bore done for the low gear pinion - it's 1.010".
I used a depth micrometre to determine the dimensions of this hole - it's a nice tool that I bought from someone at the railway a few years ago:
The whole has two diameters - one for the layshaft and one for the low gear pinion. Both of these diameters will be bushed:
The larger of the two fits the low gear pinion beautifully:
The smaller one clearly fits over the layshaft:
We can also see that the length of the 1 1/8" section is just right:
Now we need the bush, but before we make that the package from Tracy Tools has arrived with the long series drills we need to fit the kickstart pawl and it's pin but before we do that we'll spend the day driving one of these:
