Model A - kickstart shaft and a big milestone

 Today I was pleased to make the last few cuts on the main 1 1/8" diameter part of the kickstart shaft. With carbide tooling, the right geometry and the right speeds and feeds the finish comes up very well and the fit is spot on.

The next job is to mark out and cut the 3/4" diameter for the kickstart lever:

I cut that in about 8 passes and followed it up with my form tool to generate the gentle radius on the end:

Unfortunately the inside diameter of the kickstart shaft is not round - I guess this is to be expected as it has been fitted with a cotter which pulls over to one side and has probably distorted the eye. I may have to obtain a 3/4" expanding reamer to sort this out - you can get cheap ones for about £15.

I'll probably leave ordering that until I've started milling and have worked out what other cutters I might need to buy. 

Fitting the kickstart shaft from the right side of the gearbox and cover reveals that it fits nicely:

I didn't expect this snag though. What we looking at is the stop that limits movement of the shaft - the bit I didn't expect was that these stops are riveted in place and cannot be removed, which means I can't check the length of the 1 1/8" section until I've milled the slot that this stop fits in.

Some measuring suggests that the length is acceptable - maybe even a little long, but only a couple of millimetres at the most. 

So the next step is to start thinking about the milling side of the work and to do this we need to have a flange machined into the waste in order to retain the shaft on the rotary table:

Second thing we need here is a 5 mm hole in the end, where the revolving centre is at the moment, to locate the shaft centrally on the rotary table. We will probably have to make some special washers to hold the flange to the table but more of that later.

So that was a good day of progress.

And the milestone? O yes! This week the blog has passed a million hits!

Mini-lathe - still making chips

 You might be wondering what happened to the Model A kickstart shaft project: well, despite various distractions we are still making chips. 

As you might imagine it's taking a while to reduce a 2-in chunk of EN16 to the main shaft diameter of 1 1/8" but we are getting there slowly. 

Currently I'm troubled by the finish I'm getting as I rattle through hogging out the material. I'm running at 700 rpm taking 15 thou cuts with a carbide tool - actually a selection of carbide tools. Yesterday I locked down the compound slide and tightened the gibs on the cross slide and we'll see if that improves matters. Right now the finish looks like a very coarse thread: 

Since we are not in any hurry for this part I think I will look for play in the saddle. Others have suggested removing the compound slide, checking the tool height - suggesting it's too high, changing the revolving centre for a carbide tipped fixed centre, and changing the tool for one with a wider tip, like a parting tool.

The tool height appeared to be the problem - this is much better:

Charlie's Shed - Chemical Blacking

 Way back in the dim and distant, when I was rebuilding my SQ4 in fact, I had an incomplete set of engine bolts so the SQ4, like the FH years later, wears stainless steel fasteners everywhere. That incomplete set was chemically blacked, a process which was almost universal for protecting fasteners from corrosion until the 1940's, when Cadmium plating became popular.

Cadmium is pretty toxic, and by the mid 1980's most fasteners were zinc plated - a process very much in use today.

However! Our Model A is not going to be wearing shiny fasteners, which raises a little machining challenge! The issue is, when we are missing fasteners, the ones that are commercially available are either stainless or zinc plated - and will probably not be the right pattern - we don't want nuts with both sides chamfered or bolts with stamped text on the heads! Secondly I don't want to spend hours removing zinc plating, so we will make the missing fasteners on the lathe.

Here's a batch of 1/2" CEI nuts I made earlier:

So here goes. This is the GP Cool Black Metal Blackening Kit from Gateros Plating, and if I recall correctly this is the 1 litre kit.

Here are the instructions:

For the first try I followed Process 2 in the instructions, with 3 minutes in Cool Black solution and drying the Rogard Supreme Seal with the hot air gun. A bit patchy but an online video for another manufacturer's kit suggests that 5 minutes in the alkaline cleaner is required, not the quick dip & wiggle that it got from me.

For the second job, I used Process 1 with two minutes in the Cool Black solution:

Third job: a wash with carb cleaner, 2 minutes in the alkaline cleaner, 2 minutes in the activator, 2 minutes in the cool black, 2 minutes in the oil. Much better:

The ambient temperature here is about 5°C, and I am doing this in an unheated workshop!

I think I'm getting the hang of this now. This is a spacer for the frame stud near the top of the gearbox, and after a dose of carb cleaner and a rub over with a rag and a brush dipped in alkaline cleaner it was unable to pass a water break test. I dipped it in the alkaline cleaner again for 5 minutes after which it successfully passed the test. This was followed by 1 minute in the activator and 2 minutes the cool black - this picture was taken after the first 30 second dip in Rogard: 

This is the finished spacer - which ironically I'm not going to use - it's now had three dips in Rogard and one dip in dewatering oil.

I'm calling that a success.

Model A - getting into the gearbox

 I've now completed the footrest and brake pedal area and I have the lathe up and running again after the feed gear upgrade so it's time to get back to the gearbox and particularly the kickstart shaft. 

I've not had the gearbox out before so given that the clutch is off I'll go in there, clean it up and do a few jobs. The first step is to remove the oil tank and the battery tray, then you can remove the four nuts under the gearbox and lift it out.

It's in pretty good shape externally - there's no major damage and aside from the kickstart shaft nothing missing. There are a couple of little jobs: 

• One of the 5/16 studs retaining the frame bracket is missing, 
• There is some damage around the gearbox casting for these studs 
• The gearbox adjuster bolt is broken

First, a couple of general views:

With the gearbox out, we can attend to the bent bracket that the adjuster locates in. Somebody has obviously forced the gearbox adjuster without undoing the nuts underneath, bending the plate and breaking the adjuster - it's astonishing how ham fisted some people can be!

Five minutes with a hammer sorted that out.

The outside is a little bit grubby, but more worrying is the state of the bearings on the main shaft and the sleeve gear. I'm told that the sleeve gear bearing is available, but expensive - I doubt if you can get the bushes for the mainshaft though...

The next job is to remove the broken adjuster bolt. Fortunately it drills easily:

The bolt is not seized in place and comes out quite easily with the EZ-Out:

I have a new bolt available from AOMCC Black Ariel spares and after I have run a tap into the hole it fits back on with some Copper-Ease:

Apparently there is supposed to be a spring under that screw adjuster.

The next job is to sort this out. All we need here is a new stud - 1-in long with a 5/16 BSW at one end and 5/16 CEI at the other. 

What is a bit more puzzling is that the lug on the gearbox does not line up with the engine plate so perhaps there is a thick washer in here:

And as if by magic, a new stud appears courtesy of the mini-lathe and some 5/16" round bar:

And later, a 1" diameter, 1/4" thick spacer:

All I have to do now is sort out the mixed-up 1/2" diameter engine studs - or 'tie bolts' as Ariel call them and we are done with making & mending on the outside of the gearbox. 

Investigation showed I had three 3 5/8" studs, instead of two and one 4" stud. I made a new stud on the lathe, cleaned all the others and built it up again:

The spacer went in the spares box. According to the combined wisdom and photographic evidence provided by the AOMCC FB Group, there should be a half nut there - Ariel would have listed a spacer in the parts book but not a half nut - standard nuts are never listed.

We are calling that area done.

Mini-lathe - first commercial job!

Part of the deal to get the larger lathe feed gears printed was that the owner of Regenerate3D, James, needed some aluminium parts machined for a radio controlled glider. The bit he needed was an adaptor to go between a motor shaft and a printed propeller. I agreed to make the bits to his drawing and we corresponded for a few days refining his design.

One of the most interesting bits of machining anything is working out the best sequence of operations and I'll show you what I did here but I can't pretend it was the best sequence!

The first step was to cut a chunk of 1" 6021 round bar, face one end in the lathe and reduce it a little so that it would go further into the chuck. I then turned it around to machine the other end to something close to the finished state:

Next step was a face knurl, which I had never done before. I used an existing wheel and made a little holder for it with a bit of 10 mm round bar. The washers are there to prevent the wheel contacting the work. The issue is to get the knurl close in to the centre means you cannot have anything protruding beyond the wheel - so there is no room for a nut or screw head to retain the knurling wheel.

I was very pleased with how it came out, and turned the work around to finish the other end to the same standard. At this point I still had a half millimetre oversized on the journal that would carry the propeller.

I replaced the chuck with the ER25 collet to hold the work whilst I parted it off - this was a mistake, because there was not enough length available to hold the work in the collet to withstand the parting off loads. I should have sawn them in two. Fortunately I hadn't taken any of the diameters down to size and I was able to remove the scuff marks caused by the work moving in the collet. 

Once I had the two bits separated, I could drill the holes for the grub screws. There's a chamfer behind that flange which is out of shot here and I made sure that the holes were drilled and tapped before I formed that chamfer, to give me enough room to hold the part for drilling.



This is the 3D printed propeller that will be used to launch the glider into the sky:



Here is the rear view. You can see the chamfer that I was talking about earlier:



The propeller is actually in two parts - there is an M8 nut hidden inside which retains the prop to the aluminium adapter.