Monday, 29 October 2012

Braking News

These past few shedweeks, I've been making a couple of pivotal components for the geared facile.

Specifically the two pivot mounts for the brake lever and the spoon brake. As mentioned last time, these were almost certainly off the shelf items supplied by Snell & Brown. I'm slowly making all the bits necessary for the handlebars to be brazed up, without actually making the handlebars, I'm still pondering on that chewy little problem. The success of a project like this is in the small details and as mentioned last time, I enjoy small details. Little bits like the lever mounts have to be accurate for the machine as a whole to be accurate.

The lever pivot would originally have been a casting and most likely from gun metal rather than steel. The original I am copying has traces of verdigris on this pivot indicating a copper content. Mine will be machined from 4140 steel, mostly because I have a suitable lump handy but also because machining this from solid will be quite wasteful and anything containing copper isn't cheap right now. Or probably ever again.

In contrast the original spoon pivot is certainly made from steel, it is a tricky little thing and while I don't need it in order to finish of the handlebar assembly, it makes sense to make it at the same time.

Notice the greenish verdigris on the lever pivot and the rust on the spoon pivot.

As usual here is a photographic recipe for cooking your own lever pivots.

Start with a suitable lump of 4140 and mount it eccentrically in the 4 jaw to bore the off centre 0.75" hole.

Then shape the sides to form the start of the convex bulge and define the width of the clamp.
Flip it around, re centre on the bore and machine the other side.

Then saw away the excess, this is the bit that would have been wasteful if using gunmetal.

Mill the upper and lower bounds.

Mill the clamp height and the excess from the round bulge.

Drill a pair of holes, one being threaded, the other just to help with metal removal.

Rough out the slot in the clamp with a saw.

Mill out the clamp slot and finally finish off with a hand file

The spoon pivot is based upon a 0.75" steel ball. On my latest trip back to Blighty just a few months ago, I purchased a ball turning lathe attachment for exactly this job and I've been itching to use it since.

Turn a piece of 4140 bar down to the rough shape.

Start turning the ball, my word, this was fun.

Thin down the threaded section to 0.25" and rough out a 26tpi thread,
this is so that the die will start straight as I'm unable to use the die in the lathe.

Then without removing from the chuck, remount in the dividing head 
and drill and tap the cross through hole at 0.25" cycle thread.

Counterbore for the screw.

Then index a quarter turn and rough mill out the slot from either side. 
Also mill through at the base of the slot.

Remove from the chuck, and saw out the narrow bridge remaining.
Saw off from the barstock and run a 0.25" cycle thread die down it.
Remount in a suitable fixture and mill the slot to final size.

Finally make the two screws for the pivots, first rough out the screw before cutting the thread.

Make a suitable arbor to hold the screw whilst the head is machined, 
first cut the dome, this is cut using the same settings as for the round ball so that it matches the profile.

Then cut the slot with a slitting saw.

The completed pivots.

Phew, that was a lot of pictures.

In other news, I've been exorcising my demons these past few weekends. Last Monday was labour day here in NZ which means a long weekend. Hoorah. The whanau decided to spend the weekend in Akaroa doing exciting holiday things. I decided to ride over following the route of Le Race. Now, I'm not as fit as I usually am at this time of year. This sorry state is due to a number of things that I'm not going to go into, but suffice to say I've been drinking a little too much as a result.

The climb up from Little River to Hilltop was OK and then the summit road was OK to. The steep bit around the back of Duvauchelle was hard but then it always is, the difficulty came on the final descent down Long Bay Road. If you recall, the last time I rode this, I liberally smeared a percentage of my skin down parts of the tarmac. I had no desire to repeat the experience and descended like a very slow descending person. I was pleased to get to the hotel in one piece.

Then this last weekend, we headed up to Hanmer Springs for the night. I usually take an offroad bike and do the loop straight up Jack's Pass, along the Clarence River and then back down Jollie's Pass. Riding up Jack's Pass was relatively hard due to the strong Nor'Wester headwind, I was blown to a stop and then forced backwards three times on the way up. Remounting on such a  steep hill into a headwind proved quite difficult, the whole time getting sandblasted by the gravel. Just before the summit of Jollie's Pass my seat post snapped clean off at the point where it enters the frame, it was a typical aluminium fracture with no prior warning. I rode the final 11km including the steep descent and back into town standing up, my thighs were burning when I got back. Nothing that a quick dip in the hot pools couldn't sort out though.

A breaked aluminium seat post, yesterday.

Wednesday, 10 October 2012

And now for something completely different

After last week's Handlebar Brouhaha, I've calmed myself by making something completely unrelated. The oilers. There are nine of these liberally sprinkled over the machine in two different sizes, small and even smaller. The vast majority of original machines I have seen are missing the oiler caps and many are missing the oilers themselves. Being tiny, made of brass and sticky outy, they tend to get knocked orf and lost.

When I mentioned my proposed shedweek activities to Mr. Middleton, he initially expressed incredulity, 2 BA oilers being a standard off the shelf item. He quickly checked himself, realising that of course I have to make them, they wouldn't be right otherwise. My lovely wife rather unkindly calls this OCD, I prefer to think of it as an attention to detail that normal people don't have.

The original machine I am copying has most of its oilers and it has one cap remaining, the one on the rear hub where it is fairly hard to get in and poke it off.

The only oiler cap surviving on the original geared facile.

A small amount of research led me to the original supplier, Snell & Brown of Birmingham, although I note that they had a London warehouse less than a mile and a half from Ellis & Co.

Clearly the oilers used are the V93 type. 

This advert from Sturmey's Indispensable Handbook for 1887. Interestingly, the brake lever and spoon pivots are also from this supplier, being items 7 & 4 resp. More on these later. Snell & Brown had folded by early June 1889 and the well known Brown Brothers company had emerged from the ashes and continued in business well into the 2nd half of the 20th century.

The oilers on the front wheel bearings and the lever pivots are slightly larger than those elsewhere, I need to make 4 small oilers and 5 tiny ones. The five smaller ones are located at each end of the connecting rods and in the rear wheel. Once again pictures can describe the machining processes used.

 Machine the brass down to the correct size for a 2BA thread.

 And then cut the thread. A tip to get the thread straight is to support the 
die holder with the drill chuck and feed it in under slight pressure whilst turning the work .

 Then drill the smaller through hole and cut off the oiler from the barstock.

 Then remount in a handy 2BA work holder and drill the larger recess.
Finally tidy up the sawn end with a 45 degree chamfer. This is the oiler complete.

 To make the cap, drill out the barstock to the same OD as the oiler.

 Then machine the outside to profile.

 Knurl the top edge of the cap.

 Remount in the dividing head to drill the 4 holes around the cap.

 Close up of the dividing operation.

 Use a junior hacksaw to make the slits to the holes.

 Cut the cap from the barstock.

 Remount in the 3 jaw using a piece of barstock and a shim to prevent crushing.

 Clean up the top of the cap.

Then repeat 8 more times. Except of course, I did nothing of the sort, instead I set up a small production line and repeated each step before retooling for the next one. History has shown us that these tend to get lost or stolen so I've made a few spares.

The small ones on the left are the main front wheel bearing and the lever pivots, 
the tiny ones on the right are for the con rods and the rear hub.

In other news, I've been painting my kids bedrooms this week. These are not included on our EQC earthquake damage claim, so we can go ahead and do them. The rest of the house of course has to wait until the men in suits with clipboards deign to give us a date when our house will be repainted/repaired. This may or may not be in my lifetime. The kids like their new colours and refer to them as their new rooms.

We had nasty little magnitude 4.2 this lunchtime. I heard it before I felt it, it wasn't large and it didn't go on for long but being the first one for a while it served as an unpleasant reminder of what we've been through these last two years.