Friday, 3 June 2022

SQ4 - Oil Leak from the Rocker Feed

 This may be a seminal moment in the history of my SQ4. For years it's had an oil leak which I have always assumed to be poorly sealed pushrod tunnels at the head joint. However, having addressed a problem with a leak from the oil tank cap, something else which it has always done, I resolved to look at the drip from the rocker feed pipe. 

The oil tank cap has always had a weep from the breather:

Which translates to a wet leg on a long, fast run:

Looking at that first picture, I got to wondering why the cap has a vent hole when the tank has a piped breather that I have taken past the rear wheel. Surely the cap should be sealed?

It turns out that Square Fours don't use the same cap as other Ariels. I noticed that the 1951 SQ4 parts list has a -32 number for the cap - most bikes (other than Square Fours) I've seen use a -29 number. Maybe 5854-32 has no breather hole.

A blob of solder will sort it.

Onto the rocker feed. I ran the engine cold (75 psi on the gauge) and as the oil warmed up the leak appeared:

Now, my bad - I forgot to take a camera to the workshop when I fixed it. It turned out the tube was not pushed into the fitting at all - it was just held in place with a fillet of solder at one end, and had been like that for years - probably eight years. It's been leaking for most of that.

All fixed now.

Wednesday, 11 May 2022

Charlie's Shed - adapting threads

The FH kit came with a lot of original Ariel cables, most of which were pretty rusty but which still had their original adjusters and nipples. The cable layout changed with the advent of the swinging arm bikes, in that the mid-length and gearbox end adjusters moved up to the handlebars for the front brake and clutch. The thing is, most of the handlebars out there use the later 5/16" BSF adjusters, but Ariel used the earlier 1/4" adjusters to the end. Guess what? Levers with 1/4" adjusters are like hen's teeth!

So what to do? after looking at eBay for ages, and noting that Draganfly are out of stock I decided to modify what I had by sleeving the existing 5/16" thread. The issue is that putting a 1/4" thread inside a 5/16" thread leaves very little wall thickness, so the part would be weak. Here's how I set about it:

First job is to turn a bit of scrap brass to the correct OD - 5/16", and put a thread on it - these are BSF threads in these levers, by the way - so it's 5/16" x 22 tpi. Next, we can drill a hole, tapping size for 1/4" BSF, but we won't tap it yet. Next we can try it out in the lever perch and if all is well retain it with some Loctite 263 high strength thread locker:

Next job it to file the ends flush, and tap the hole. Currently I don't have a tap long enough to go all the way through, but it's long enough for the adjuster. Cut the cable slot with a hack saw and a needle file:

Job done!

Tuesday, 10 May 2022

FH Dry Build - Speedometer Bracket

Today's little bit of progress is this - a speedometer bracket folded up from a scrap of flat bar. 

Monday, 9 May 2022

FH Dry Build - Carburetter

 Some while back, actually in this post, I outlined the trial fit of the carburetter and the fact that the shiny new bell mouth didn't fit very well - as you see here:

Having checked the threads for damage I concluded that the undercut on the carburetter body wasn't deep enough, and/or that the last thread was not cut fully to depth since the new bell mouth did not want to screw fully on. 

I noticed that the horrible plastic one had a short length where the thread was relieved, and not wishing to set the carburetter up on a face plate and recut both the thread and the undercut, I put the bell mouth in the three jaw chuck very lightly to avoid distorting it:

I relieved the thread with some very light cuts for a few millimetres - the bell mouth fits perfectly now:

Sunday, 24 April 2022

SQ4 Luggage Carrier

 The Four has never had a luggage carrier - they are pretty unusual for that period in Ariel history if surviving examples are anything to go by. Tom and I have a notion to do the VMCC Round Norfolk run this year, and I had realised that I really needed something better than 1958 Pattern Webbing 'Large Packs' suspended from the rear mudguard.

So, we start with the carrier - the ladder part is available from AOMCC Singles Spares:

It’s very nice indeed - 18 swg cold rolled sheet. Loosely laid on the lifting handle, which is not fitted when the carrier is used we can see how it’s going to look:

The members of the ladder frame are about 1/2" wide, so we will use 1/2" tubing for the stays.

The rear stays are swaged to one side - I have arranged two heavy rolled steel angles in the vice with the tube clamped against them, and I squash the tube between this and one side of my swaging die, as shown below:

The test piece comes out reasonably well:

The front stays are swaged both sides, so I need two shaped swaging dies:

The first attempt at rear stays is a bit long, leading to the carrier sitting too high:

I believe this is Markus Nikot's KH, with original carrier. See how low it is compared to the rib in the mudguard?

Shortening the stays has mine in a similar position:

Now, it doesn't appear that the ladder provides the strength the carrier needs to replace the lifting handle, or to carry much of a load without failing through fatigue so we will connect the front and rear stays with a solid 3/8" bar. The bends in these are made with a mitre cut 2/3 of the way through the bar and welded up again:

The original luggage carrier on my Model A has the rearmost member, the one you want to grip to pull the bike onto the rear stand, rolled into a tubular shape around a solid bar - which makes it much nicer to hold. I've replicated the arrangement with a piece of 3/8" folded into the rear-most rung of the ladder:

Here it is, swaged in:

Next step is to weld the bars into the stays while they are in position on the bike. These are just tacks, and the welds were completed off the bike:

The carrier is coming on nicely and looks the part. Having got this far, I could investigate how the carrier interrupted the raising of the mudguard; in fact, the guard hits the wheel at the bottom long before the carrier hits the seat, so you have to remove the wheel to find out if it really still works.

Here's the round lifting bar welded in at each end:

The next step is to attach the ladder to the side bars. I want to preserve the shape of the pressing, so I have decided to plug weld the ladder to the bars from above. I've realised that the secret to good plug welding is to drill a big enough hole such that the arc strikes the bar underneath, and not the edge of the hole - then you can back fill the hole completing the weld in a controlled fashion. These holes are 8 mm:

I tacked through these holes to fix the whole carrier together whilst it was still on the bike. When I removed it, I welded the stays to the carrier on the inside, and left the outside free of weld to emulate the original.

Next I finished off the plug welds:

The final step is to dress the welds and apply some paint, then when it's dry and hard we can reassemble the back end of the bike.

And here it is, with several coats of U-Pol:

It's actually bent down slightly at the front, drive side corner

It might need a bit of adjustment, but it looks good for now!