Sunday, 4 April 2021

QR50 - Fabricating the Airbox

Building a replica airbox seems like overkill for a little motocross bike that's going to be worth a few hundred quid when done, doesn't it. The original plan was to use a cheapo Chinese pod filter on the carburetter intake, £6 max and you are done, and maybe put a toolbox in the airbox space. However, as usual my OCD took over and fuelled by the fact that the carburetter moves relative to the frame and a pod filter wouldn't fit in the space available without an elbow, and then it would need support... you see how the job grows. I elected to fabricate the airbox along the lines of the original - then I'd have support, the space filled, an air filter, no cash outlay and something that could accommodate the carburetter moving up and down. Plus, I'd have more experience to help when I came to manufacture the toolboxes for the 1930 Ariel Model A.

So, out with the cardboard to make a model, the beginning of a lot of my fabrication jobs. Cardboard is great - you can make an airbox, cut it where it doesn't fit, take it apart, make a better one and eventually you end up with one that fits, like this one:

Here it is in situ:

The next step is to cut it apart again and make the net - the pattern that will be used to make the part in steel. I like to use these magnets to hold the net on the piece of sheet - this is 0.9 mm thick cold rolled sheet, part of an old bread bin.

You can use the bandsaw to cut this stuff easily, though some of the internal features need a file. It's important to deburr and to file your corners square before you start folding:

First job, cut the hole for the air outlet. Normally, it's better to cut holes after bending when the hole is near a fold, because the bending the sheet will stretch the hole out of shape. In this case, I wanted to corner weld the tube in from inside, so the hole had to be cut and the weld completed before the sides were folded up. It's critical to plan the process to make the folds as easy as possible - it is all too easy to make one fold only to realise you have prevented yourself getting access to make the next one.

I always drill holes using cone drills - it's much easier to get a circular hole in sheet metal than using a twist drill.

The air goes into the carburetter through a 1" tube, welded into the box:

The most complex fold is this curve - it's there to go around the frame. I made it round a bit of scaffold pole and when it was almost there I folded up the sides to make sure it was the right shape

In case you were wondering, I burnt the blue powder coat off...

At this stage, I welded up the edges of the curve, before I made the next folds - to ensure the material would stay in place while I subjected it to more bending. This picture shows most of the bends complete and welded:

Here, I've folded up the flanged edges and tacked on the lower mounting bracket. The tube going to the carburetter has been trimmed to length:

This is the lid, made in a similar way:

Back to the airbox again, this blue panel supports the foam:

Here's the other side, showing the inlet to the airbox which shields the oil line banjo and ensures the air inlet is protected from flapping trousers:

View from the front. That nut is attached to a stud that passes right through the lid, filter element and box and is welded into the back of the box:

Next I spent half an hour tidying up some welds - I used the linisher, some files and a small wheel in the Dremel just to smooth it out before painting. It's not perfect - I'm not spending hundreds of hours ironing out every nick and scratch but we will tidy up the worst of it. So next it's paint, starting as usual with U-POL etch primer.

Here's the completed airbox, coated in U-POL satin matt black. The parts are held together with hot melt adhesive and the element is hand cut from a piece of open cell foam:

Thursday, 18 March 2021

Model A - repairing threads

It's a wet day here in Norfolk, and I have some domestic stuff to do in the workshop so while I'm at it I might get distracted...

I'm looking at the workshop layout with a view to getting a bike lift in there, so I have shuffled them around and the Model A happens to be accessible, so we will have a look at a couple of loose ends. The front mudguard has been hanging off for a while (and still is) because there are a couple of dubious threads in the forks - one, a broken bolt, and then two other threads that are just fouled.

Here's the broken one - I have put a 1/8" hole through this broken 1/4" bolt, to see if it will come out with an Easy-Out. they never do, but I have to drill the hole anyway!

Of course, it didn't come out and I moved through the drills until I was one size under tapping size for 1/4" CEI. I then applied the 1/4" CEI taper tap and used it to clear the thread - it moved the remains of the bolt:

Next stop, same problem at the back. I made the mudguard & rack fasteners a while ago and could only fit one side, because I found someone had broken one of the 3/8" bolts in the frame lug, drilled and tapped it something like 5/16" and put a new bolt in. Today, I removed the broken 3/8" stump using a diamond burr in the Dremel and chasing out with a 3/8" CEI taper tap, so this shot shows it all back together with the stand spring fitted at last:

I also took the opportunity to chase out the chain adjuster threads. Grovelling about on the floor makes me realise that a hydraulic lift would be a nice addition to the workshop!

Back at the front, I now have both sides of the mudguard stay fitted - to cut the mudguard, I need the centre bracket and the front stand fitting - unfortunately I have run out of 5/16" screws, so that's the next job.

Comparing the next picture with my picture above, you can see I have the mudguard stay too far forward:

Friday, 5 March 2021

W/NG: finally fixed?

Since the last time I wrote about the W/NG, we have been locked down again and are only now seeing the light at the end of the tunnel. We've had snow, freezing winds, and Christmas, if only for a day or two. It's had very few outings since the COVID crisis is a very bad time to be needing the services of A&E in a hurry should the worst happen so I have been painting (a house), making an airbox for the QR50 and turning parts for the Model A

However, painting a city centre house means you need to get there and park, which is much easier on a bike so I have used it a couple of times. You might recall I put an old Lodge HN in it, to see how a traditional plug would behave - well, it failed after 200 yards and a new W8AC went in. This was fine for the rest of the commute, testing the new main jet, but the high speed thrash along the main road had us arrive back coughing, spluttering and sooting up.

Back to square one. I decided to replace the float needle, which was an old one:

Can't see what's wrong with it? No, that's because it's hardly worn. The fuel level was quite high:

Messing about with the float bowl got the level down a lot:

It ticks over nicely:

I wasn't convinced that it would make the difference, and looked back over some old pictures only to realise that the throttle needle was not, in fact new... I bought another and made a comparison:

Here, I've marked the old needle (bottom) and the new needle (top) every 10 mm. The chart below shows the diameter at each position in thousandths of an inch, with the difference in the 'wear' column on the right.

When you consider that the needle jets are sold in increments of one thousandth of an inch, wear of up to six thou' in the needle is very significant.

It has to be said, this is a schoolboy error if ever there was one - I should have bought a new needle at the outset, I would have saved a fortune in spark plugs.

A 50 mph thrash down to Weybourne produced this colour in an old B5HS.

And the fuel level? I'd set the float so low that the valve could hardly open. I could ride a couple of hundred yards and then it would splutter to a halt, and I would have to wait while the float bowl filled up again!

Saturday, 20 February 2021

Model A - Fasteners on the Mini-Lathe

Updated: First published December 2020

After making some tank bolts for the W/NG, I thought I would make a start on all the missing fasteners for the Model A. After all, I like turning and I'm a bit fed up with welding after the QR50 exhaust. I'll need:

  • 2 off E1/58 special bolts for the rear stand. I have the 1/2" Thackeray washers to go with them. E1/58 was renumbered to 5505-26, which is used on the W/NG and many other Ariels. I can copy these.
  • 1 off E8/245 petrol tank bolt, like the one I made here.
  • 2 off E8/921 special bolts for the rear mudguard stays, with their nuts. The bolts look like Ariel parts 5655-30, which is used on the W/NG so I can copy these; their nuts, E8/922 are not the same so I will have to find out what these look like. Looking around the reference pictures I have, it appears the hex size on these matches the stand bolts, whilst the hex on the W/NG ones is smaller and matches the bolt they attach to.
  • E8/762, the big nuts for the top of the oil tank. These are different from the later ones as used on my W/NG and SQ4, because the oil tank bracket has a smaller hole as does the sidecar mount in the frame and the later nuts would not fit. E8/761, the stud that goes with this nut, was renumbered to 0182 and is a standard Ariel part. It's a 5/16" CEI x 1 15/16" stud.
  • The lock nuts for the chain adjusters, E8/925 renumbered to 5744-30 and the the chain adjusters themselves, E8/924 renumbered to 5740-30. Both of these are used on the W/NG so I have patterns I can copy for these.

I'm making a start with the stand bolts, since I have the Thackeray washers, the stand and and the springs. All these bits will get lost if I don't make the bolts and get them attached to the bike.

I'm starting with a bit of 0.82" hex in EN1, since I will be chemical blacking these and don't want to use stainless. In this picture I have turned the 1/2" OD register for the washer and the 3/8" major diameter for the thread

Here's the thread going on using a 3/8" CEI die in the tailstock die-holder:

Here's one, mostly finished. I have to turn a chamfer on the other side, but I will make a few more bits before I rig up for that:

Turning the head chamfer, after facing off the head and discovering that my parting tool was not quite square!

Finished and ready for blacking:

I'm going to make the E8/921 special mudguard stay bolts next, by copying the ones on the W/NG. These bikes are so easy to work on, properly designed for easy maintenance:

Here is one of the bolts, with it's locknut and the special nut which fastens the moving part of the mudguard:

Using the same set up in the lathe, same turning and parting tools, the three jaw chuck and the tailstock die holder with the 3/8" CEI die, I'll make a couple of these bolts to this stage:

Since the next stage for both these and the stand nuts requires me to put the threaded end in the chuck, I will change over to the ER25 collet chuck to avoid damage. I only want to do that once, so with the the hexagon bar stock still in the 3 jaw chuck I'll make the two special nuts:

So in this picture, we can see one of the completed E8/921 special mudguard stay bolts with it’s E8/922 nut, which retains the detachable stay. Also pictured is the E8/761 (0182) 1 15/16 stud for the top of the oil tank.

These are the E8/762 nuts that retain the oil tank to the sidecar lug. The sidecar lug is much smaller on the 1930 frame than the one on my 1942 W/NG. 

Last thing on the list is the chain adjusters. The nuts are first, and these are made from a bit of 0.445" hex in the lathe. They have a short 5/16" BSC thread inside, and most of the outside is plain:

The adjusters themselves are a bit more involved. They are basically 5/16" round bar, but they will have a 1/8" BSW size hex (3/16" BSF) which is 0.34" across flats. This is unobtainium, so I will build up the rod with weld and mill the hex in. I'll start in the lathe, just to start the threads square:

The hex is not much bigger than the diameter of the bar:

Here they are again built up with TIG. The two tubes are the footrests for the QR50.

Here's the setup in the Mini-Lathe. Usual vertical milling slide replaces the compound on the cross slide, and the rotary table is attached to the vertical slide. The saddle is locked to the bed, and the tailstock backs up the vertical slide:

We are passing the work over the cutter, to avoid making climb cuts; the plan is to make a pass, turn the table 60°, and make the next pass. After one turn we will advance the work using the vertical slide - otherwise the vertical slide is locked. I've also tightened the lock screw on the cross slide gib a bit, to take out as much play as I can:

Here's the first one. The target is a 0.340" hexagon, which is 1/8" BSW. It's barely bigger than the 5/16" bar (0.3125" diameter). Currently it is 0.007" oversize.

Next step is to tidy up the hexagon  and face the end to length, adding a small chamfer. 

Next, we'll cut the rest of the thread:

And that's it, apart from the finish:

Tuesday, 12 January 2021

Model A - First Impressions of a Clutch

Isn’t it a bit early to be looking at the clutch on that bike, when you have so many others in the pipeline I hear you ask? Well, yes it is, but a while back I lost one of the tank bolts on the W/NG - you might remember I made a new one; I am diverting myself with lathe jobs as a distraction from all the welding on the QR50, and part of the lathe work is to collect the bits for the gear control on the Model A, and to do that I need to mount the tank - which is another lathe job, as one or two of the bolts are missing - so I need the tank mounting rubbers for that too, and I also want to trial fit the tank on the FH and I have no rubbers...

So what I need to do is to get an order for Jeff Hunter Engineering, who will supply all the rubber bits and what I am going to do is order as much of the rubber as I can, for all three Ariels. And this is where the clutch comes in - the Sturmey Archer clutch in the Model A has a rubber shock absorber in the clutch and this is bound to need some attention:

So let’s have a look. It’s very easy to get to as in 1930 Ariel were not using the fully enclosed and sealed primary drive, and my primary cover is off awaiting time on the welding bench:

Clearly, two of the retaining bolts, springs and spring cups are missing. Those bolts actually have screwdriver slots under that muck.

Under the pressure plate, the basket and centre are very good indeed:

The plates are reasonable too, but I wasn’t expecting Ferodo linings:

The parts list clearly shows a cork lined clutch:

Yet if we look in the Sturmey Archer book from the period, there is a Ferodo option for the three plate clutch. Interesting.

We’ll have to replicate these parts, though I wonder if they have been intentionally omitted. Ferodo clutches of the period can be quite heavy - the one on my W/NG is much less pleasant than the cork clutch on the SQ4, for example.

Still, it will be a long time before we have to deal with that problem.