FH - primary case again

 Just a small update today. The primary case is now on and together; I fitted the outer cover with a gasket with Wellseal on the outside and grease on the inside. It took a while to identify all the screws (stainless steel from Acme), but it's finally together. 

The clutch basket is a trial fit for the moment - I haven't bent up the tab washer yet.

FH - clutch pushrod

 I usually make clutch pushrods for the simple reason that by the time I find that I need one I don't usually have the time to order one from one of the main suppliers. You can make them very easily with material from eBay or somewhere like that: they're just a 1/4" round silver steel bar cut to an appropriate length. Most Ariel ones are around 12 1/2" for the CP & BA boxes; later models with GB gearboxes are around 9 1/2" or so and are 5/16" diameter. Don't take these figures as gospel since there are a number of different variations in length due to different mainshaft lengths, different numbers of clutch plates, and the presence of friction material in the clutch basket in the last machines.

When you obtain the steel it will be in normal condition and will require the ends to be hardened. This is very simple - All you need to do to harden the steel is to heat the end to cherry red and quench it in water. 

First, before hardening you want to cut the rod to the right length. It's easy to find the right length, because the wonderful people at Draganfly provide a parts list which has the lengths recorded. If you're feeling guilty about using their information but not buying the parts rest assured that you'll be buying lots of bits from them at some point or other!

Start by marking and cutting the steel to the right length.

Next you'll want to square up the ends and smooth them off. You can use a file for this but I usually use my bench linisher with the mitre attachment set to 90°. With the end squared off I like to put a tiny bevel on the edges just to soften them.

Next step is to heat the ends and harden them. Some while ago I took one of the mini beer kegs and turned it into a small furnace with some ceramic blanket and fire cement. It makes heating this kind of thing very much more efficient, because it contains the heat from the torch. You use a lot less gas and the whole job heats up a lot more quickly.

Next you just plunge the end into a cold water bath, and turn around and do the other end; the middle part of the bar doesn't need to be hardened. You can clean off the oxide colours if you want to but it's not necessary. 

Pop your push rod into the main shaft and you're ready to build the clutch. 

By the way, these pictures show a 1/4" pushrod in a 5/16" hole. You live and learn!

FH - fitting the cylinder head

 Fitting the cylinder head didn't prove to be the routine operation that I had envisaged. I started with a coat of Wellseal on the top of the block and on the top of the gasket. Prior to this I had cleaned out the threads in the block with a new tap and cleaned the threads on the head bolts with a new die. Two of the head bolts were damaged and needed replacement.

Lowering the heavy head into place was the usual faff but eventually I got a couple of the bolts dropped in on the near side. I wanted to put the corresponding bolts in on the far side next but for some reason I couldn't get them to mate with the threats in the barrel. After a lot of messing about I pulled the head off again to have a look:

It's sometimes a challenge when you buy pattern parts - in this case you can see that the bolt pattern in the gasket is wrong and the holes don't line up. I decided, rather than to use the composite gasket in the kit, that I would anneal the original gasket and reuse it. This is very straightforward - it's just a question of heating the copper to cherry red and leaving it to cool followed by a clean up with some Scotchbrite pad.

After that, and a second coat of Wellseal, the head bolts all went in easily. Neither Ariel nor the BSA service sheets indicate a recommended torque for these bolts but they do show a pattern you have to follow when tightening them up:

All that went swimmingly, as expected, and we now have the head fitted. Of course fitting the head opens up whole new set of work faces including the carburettor, the rocker box and the exhaust pipes. OK, the exhausts will have to wait until I have finished the primary case and I'm going to repair the stops on the centre stand as well since access will be better without the pipes in place.

More later.

FH - primary case

 I've bought (from Simply Bearings) and fitted a new spring link to the primary chain, tensioned it, bolted the gearbox up tight and finished the crankshaft shock absorber.

I spragged the sprockets like this:

There's definitely a split pin in the crankshaft shock absorber nut!

FH - dual seat

 After a lot of welding and modifications to the seat base to accommodate threaded fasteners, all previously shown in the blog, it's time to finish the seat. 

The first job, and this is part of painting activity, is to get the seat base coated with two-pack:

With the seat base on the bench we put some strips of double-sided tape on top of base. This is going to retain the rubber and stop it sliding about as we try to fit the cover.

This is the original foam rubber:

This is probably not the original cover, because it's PVC and not Rexine. I might be wrong of course because I don't really know when the industry stopped using Rexine for seat covers; all I can say is that my 1960s cars always had Rexine covers and not this very compliant PVC material.

The key thing with these covers is to make sure that the orientation of the seams line up with the appropriate parts of the base. Once this is done, it's sensible to retain them with as many clamps as possible. I've got a lot of these little spring clamps, which are very cheap, just for this job and a million others:

I've experimented with the different areas around the edge of the seat base to decide where I should start gluing. Some areas are much easier to access than others and some areas prevent access to other areas when folded over.

I'm using a contact adhesive from Screwfix which I use for laying lino. It seems to work very well and goes off in a couple of minutes. I've started at the front of the base and held it all in place with three large clamps. When this has dried enough to be very sticky I move backwards down both sides of the seat simultaneously.

When the sides are done I move on to the back. This is the most difficult bit, but cutting darts into the cover enables the glue joints to sit down quite nicely. You tend to go around the cover pushing the fabric into place as the glue goes off. I used a small hammer to knock the retaining spikes back because actually the glue does a far better job than those little metal spikes which are never in the right place.

That's it, finished and ready to go back on the bike.

I think it looks great. Some people think the seat looks better in black, but the tan colour is very characteristic to Ariel and I like it.

FH - rebuilding the ATD

 The only job that's getting in the way of timing the engine is the rebuild of the automatic timing device or ATD. I've got a kit with excellent instructions from Priory Magnetos, and this will replace the fibre gear and the springs on the old original timing unit.

The first part of the job is to remove this collar which holds the whole unit together:

After various activities with old cars in the past I've got a number of different pullers and ball joint splitters and all sorts of things like that knocking about. This bearing puller make sure work of grabbing hold of the collar and pulling it off:

The colour allows you to release part of the ATD from the section that carries the fibre wheel. The next job is to use a 3/16 drill to remove the rivet heads that hold the ATD to the fibre wheel. The pillar drill makes sure work of this little job:

You can then knock the rivets out, and essentially the whole thing will fall apart. You might have to untangle the springs and the bob weights but that's as far as it goes. This the units now completely disassembled and it's had a little while in the cleaning tank to get rid of all the old oil.

The next job is to replace the fibre wheel with the new rivets that are supplied in the kit. Before I do that I have a good look at all the parts to make sure there is no damage. In fact the unit has been a part before because one of the stops that prevents the unit over advancing has actually been replaced by some thinner piece of material braised in place. It seems to be in about the right place and it functions so we'll leave it as is. The second problem is the back plate is a little bit bent for some reason but that strains out quite easily with a small hammer and some judiciously placed taps.

With all that straightened out, we can rebuild the ATD using some new rivets and a new fibre wheel from priory magnetos. This goes together quite easily and it's riveted up using the ball pein of my hammer.

With the rivets in, we can assemble the loose parts of the ATD using some new springs and some lubrication for the moving parts. Then we can put the unit in the vise and squeeze up to refit the collar.

That's it, done for now until we're ready to time the engine.

Mini-Lathe - torque upgrade

 Inspired by Ted Hansen's book, I resolved to increase the torque available at the chuck using a smaller motor pulley.

Ted provides all the details of how to make a new pulley in his book. However I reasoned that if I could learn how to specify a timing belt pulley, which would entail learning how to specify timing belts, I would probably be able to find a ready-made pulley that I could buy. The target pulley: 12 teeth, 8 mm bore, 10 mm wide.

The standard pulley has 17 teeth; moving to a 12 tooth pulley should give us a 28% torque increase.

I discovered that timing belts typically come in a variety of forms centred around the shape of the teeth. The lathe uses a belt which has a trapezoidal form, and this is called an AT format belt. The pitch of the teeth is 5 mm which makes it an AT5 belt and it's quite easy to find an AT5 format pulley with a 10 mm width. The difficult bit is that the hub is typically quite small - the one I found had a 10 mm diameter hub which I needed to bore to 8 mm, which therefore has no room in the hub for a grub screw: the screw had to be drilled and fitted between the teeth of the pulley.

With the new pulley in place, I spent some time adjusting the level of the motor such that the belt would run in the middle of the pulley. From the dust on the end of the motor it appeared that the original pulley had allowed the belt to rub against one end and slowly abrade the belt.

With the adjustments I made the belt now runs in the centre of the new pulley which should lead to less wear. 

You can notice the change in motor speed versus the spindle speed now that the gearing has changed but you will have to wait for the next instalment to hear if this has made a difference to the depth of cut that I can successfully achieve.

FH - cylinder head refurbishment

 Inspecting the cylinder head of the Huntmaster revealed that the valves and particularly the guides were very poor shape. There was 2 mm of movement at the edge of the valves when they were in the open position - so they were going to have to come out.

As you can see a lot of carbon came out with them.

Feked provided a set of valves, guides and springs at a very decent price. I guess the fact that these are BSA A10 parts provides some economy of scale.

The new guides are 0.565" diameter; the old ones are 0.562". Guide bores measure 0.561 - 0.5615". The most interference we would want would be 0.0015”, especially if they are cast iron guides - and even at that they would need reaming to finished size after fitting. That means the guides need to be 0.5625 - 0.563 for a 1 1/2 thou interference fit or 0.562 - 0.5625 for a 1 thou fit.

It was quite tricky to take two thou off on a lathe whose bearings allow half a thou movement on the diameter but I persisted, setting them up with the DTI in the ER25 collet chuck which worked rather well. In the end I got them down to the required diameter.

With them all done and the oven hot after a chicken and chips dinner I decided to put them in one afternoon. The valve guides spent half an hour in the freezer whilst the head spent half an hour in the oven set to maximum. In the event the infrared thermometer showed a temperature of 248° C and I was happy with that.

The guides went in relatively easily with help from a small hammer and a drift made from aluminium and bought from Feked; this was ok but I thought a little soft and probably not worth the money. I should have made one from steel.

I discovered during the process that the spring seats did actually fit around the guides and not under them. I wish I had realised that (or at least checked) before I started the work.

The valve seats were badly pocketed as you can see in the picture below. There was really no choice but to recut these and I deliberated for a while over whether to do it myself or to subcontract work to someone else. In the end I don't know why I bothered contemplating it really because it always comes down to the same thing - I'll have a go myself.

Cutting seats in a cast iron head is not reputed to be particularly difficult and indeed these relatively cheap eBay cutters did the job. They did however leave some chatter marks which I was able to refine I gently re-cutting again and again and eventually I got myself to a point where I used the grinding paste technique to remove the last marks.

After a bit of grinding with coarse and fine pastes this doesn't look too bad.

However if you look closely in both of these pictures you can see that the marks are not completely gone and not wishing to remove the head again anytime soon or worse to burn my new valves I resolved to do something better.

I made this cone on the lathe complete with a half inch UNF thread in the middle to fit the same mandrel that the valve seat cutters came with. When I had mostly finished the cone on the lathe I put the mandrel with the cone fitted in the chuck and made my finishing cut on the cone to ensure that the cone was concentric with the mandrel and hence concentric with the valve guide.

That bit of cardboard in the foreground is the template with which you can cut the correct section out of the sheet of wet and dry paper. The system worked well and I was now able to fit the valves.

There's some cleaning up left to do on those gasket faces where I've overpainted a little but essentially the head is ready for fitting.

FH - preparing the clutch

 Next up after the primary case is the clutch. I have the whole clutch that came with the FH kit but I've not had a look at it yet. Let's see what we have.

First of all let's have a look at the clutch centre. As expected and like most Ariel clutches that I have seen the grooves in clutch centre that carry the plain plates are deeply notched. This is useless and will have to be replaced otherwise the clutch will never release cleanly.

The rest of the clutch though is pretty good if greasy. First of all I'll clean it in paraffin tank and set it aside to dry for a day or two.

Meanwhile I bought a few bits from the AOMCC gearbox spares specialist. This includes a new clutch centre spring studs set screws for the basket and a couple of tab washers, and as usual the parts are available at a good price, are delivered very quickly and are very good quality:

When the parts I've washed are dry I've wiped them over with a blue paper towel. The clutch basket, which is of later type with friction material riveted to the basket responds well to an additional clean in a solvent.

FH - preparing the primary drive

There are a lot of work faces appearing on the bike now the cylinder head is ready to go on; the timing side can be assembled once the automatic timing device is finished and the primary side can have the clutch fitted and the primary chain built up. For no particular reason I've elected to start on the primary side mainly because I don't have the bench space at the moment to do the ATC. Here I've fitted the 19 tooth standard gearbox sprocket with a spare secondary chain and torqued up the big nut.

 

The spare length of chain I had knocking about was too short so I've taken this unusual approach of wiring it through the holes in the sprocket just to allow me to use the back brake to tighten up the gearbox sprocket nut.

With that done we can start looking at fitting the inner primary case half. What's different about this bike is that it's fitted with the fully enclosed rear chain case (FERC) something I have not yet experienced on an Ariel. There are a couple of unusual mounting points, one of which is this nut which is attached to the front half of the FERC.

It's a 1/4 in CEI bolt which needs a special tab washer to retain it to the inner primary chain case casting and to prevent it coming undone, dropping into your primary drive. The special lock washer is available from Draganfly but unfortunately I forgot to order one. I've made this one out of a piece of 0.9 mm sheet steel.

Here it is with the bolt tight and the tab washer folded up.

For the record I have fitted that 1/4" BSW screw with low strength threadlock from Loctite. The castellated nut retaining the engine shaft shock absorber will need a split pin to prevent it falling off.

That's it for now; the next step will be to think about the clutch. I expect to find some parts that are in need of replacement so I'll have a look at the clutch soon to get those on order.

For now, let's just record that I fitted a new length of primary chain and an old spring link just for now. I'll have to order a new one. 

The other thing to bear in mind is that the chainwheel is rubbing on the oil catcher so I'll have to sort that out before I put primary case outer cover on.