The Trampoline Road Trip

As I mentioned last time, our family has other stuff going on at present. Even so, I was surprised that I haven't posted for so long. I'll try to remedy that in future. My apologies.

So this past few shedweeks I've been sneaking in a little time to make all of the components for the pivots, there are five of them, two pairs and one odd one. They are all more or less the same size although some have flats and some have slots but broadly speaking they are all the same.

I thought that given that most of the work is simple turning I'd be able to knock them out quite quickly. As always things progressed slower than expected.

The pivots themselves are turned between centres so that I can do the same operation on all five at once before moving onto the next machining job. The photos are therefore not necessarily of the same pivot.

 The first job is to rough out the bearing surface...

...before polishing...

...and checking for size.

Next thin the shaft and cut the thread on the end.

Flip it around and machine the other end to size and cut the second thread. 

Note that the driving dog is an old wingnut. I like cycle threads, I may have mentioned this before.

Some of the pivots have flats...

...and some have slots.

The next job is to make the cones that make the other end of the bearing. These can't be turned between centres, so starting with a suitably long piece of bar stock

Rough out and polish the bearing surface, then drill and tap the centre (not pictured). Part off.

Next make an arbor to hold these parted off cones to machine the recess into the obverse. 

This will ensure that it remains concentric with the thread.

The last job on the cones is to slit through the recess so that it can be adjusted by a tool I haven't made yet.

The washers turned out to be tricky little blighters and I had two attempts before I was happy.

First job is to mark out and very carefully file out the holes to be a tight fit on each of the pivots. 

I bought some hugely expensive needle files just for this. I like filing, I may possibly have mentioned that before.

Next chop out and mount on a suitable arbor between centres so that they can all be turned down to size in one go.

The last parts are the nuts, there are 5 smaller locking nuts for the bearing cones and 5 larger nuts to secure the pivots to the various bits of lever, crank or frame. They are both the same design and the machining operations were identical for both. I had enough scrap steel for the smaller ones but I needed to do a raid on Kung Fu Pete's scrap bin for the larger 3/8" gauge plate.

The first job is to drill and tap the holes.

Then using the same technique as for the washer, chop out and mount on a mandrel.

Turn down to size and then...

...use the dividing head to slit both sides at 180 degrees. These nuts also require a tool that I haven't made yet

The one on the left is the odd one out and the only bearing that fully rotates at the top of the right hand con rod. 

The next two short ones are the two at the bottom of each con rod, these only oscillate. The longer two on the right are also slightly larger in diameter and are for the lever pivots, they also only oscillate.

Those bits requiring hardening have been taken in today. I should get them back tomorrow. then I can plate and paint as appropriate.

Hey guess what? I've only got the levers left to make. Hoorah.


In other news, Kung Fu Pete suggested a road trip last weekend. He'd bought his kids a trampoline on TradeMe (domestic version of Ebay) and it was pick up only from Methven. We got busy planning the route to collect as many new old velodromes as possible. Google Maps on satellite view is the primary tool but care must be used in this part of the world as horse racing and training is big business around here. Almost all old genuine velodromes are located in reserves or domains, public land in other words. Canterbury has a rich cycling past and most towns of any size at some point from the 1880's on took the trouble to build a local velodrome. We have to do an actual field visit to walk the site and physically verify the track. We then need to find historical documentation to back this up. The website papers past is extremely useful here, as we can often find newspaper reports of race meets. We've also found that a quick visit to the local settlers museums can yield local photographs and often staff either remember details themselves or can point us at people still alive that can. It's a harmless hobby and I've been doing it for years now, initially in England but now in NZ where the density is much greater and the pickings are much richer.

So this trip we collected Oxford, Pearson Park. Then a slight detour to go and visit the Secret Steam Railway Locomotive Graveyard. I hadn't been for a few years and it took some scrambling through bush to get there. I scored a deep scratch on my knee that I later told my kids was caused by a rare NZ bear. It's a long story.

I can't remember if there are 11 or 14 dead steam engines visible here. 

When they had reached the end of their useful life they were towed to where the lines crossed rivers that were causing erosion to the railway embankments. They were jacked up and toppled into the water to help prevent this. Amazing eh?

Then back on route to collect Springfield. Kowai Pass Reserve. An unusual shape but still very visible on the ground and has documented bicycle race history. Whilst in the area we both simultaneously spotted a 1930's Jones Special under a tree, It had full BSA kit including a cam rear hub and a Major Taylor stem. The owner wouldn't sell it but I haven't given up yet.

Then onto Glentunnel where we knew cycle racing took place in the 1890's but not where. Nothing visible in the domain but the museum was open so we popped in and were shown a photo from the right era of the local club. The curator told us that racing took place around the pond above 11a Railway Terrace. The pond froze in winter and provided an ice rink and then dried up in summer and provided the velodrome. The same man promised to look into the Springfield track for us.

Onto Methven to collect the trampoline and then down to Tinwald to collect the double velodromes (It's a sign, what can it mean?). When the new one was built there was debate over whether to build it in a new spot or over the top of the original. The original has people camping on it at present, I wonder if they know what it was.

Then up to Rakaia, the domain took some finding but has the most pristine example we've found yet, It was beautiful. Then over the river where we decided to leave Southbridge for another time. A quick dash up Telegraph road to Kirwee to check out the domain there. Telegraph road now has a distinct kink in it due to the recent rupturing of the Greendale Fault that has caused us all so much trouble. The road moved by half the width of the road. There was nothing to see in Kirwee so we just drove back from there. my lovely wife having only signed my pass for the afternoon.

We already have another road trip planned in the near future to collect a few more examples. We've now found that looking for documentation from old newspapers and then trying to locate the tracks is a better approach, we now have at least another 5 to tick off. It seems that cycle track racing was an enormously popular sport here in the outer colonies even as early as the 1880s. The density of tracks being built during this period is incredible. These tracks attracted the top stars from around the world. More later as we find it.

The planet gets a wedgie

I have been otherwise engaged these past few weeks. All will be disclosed in the fullness of time I imagine. What this means is that I haven't actually had much good quality shed time lately. I have managed to make the locking bits for the gear side con rod however. These are the tight fitting wedge and the bearing locking dog.

The wedge was roughly milled using the same techniques as the sun gear wedge. The planet gear wedge is slightly longer though and I had to machine it eccentrically to get the width I needed from the scrap of bar stock I used.

Mill out the D shaped profile.

And then mill the 4 degree angle to the wedge. Very careful measurements were taken to ensure the wedge didn't get too skinny and pull too far up the ramp. I don't yet have a machine to mill metal back on again.

Milling the ramp.

Then the wedge can be cleaned up and marked and cut to the correct length.

Finally do a trial fit. Lovely.

Next machine the screw to pull the wedge up the ramp and lock the con road to the planet gear.

Cut the 1BA thread.

Machine a slight dome to the cap with my ball turning attachment. The screw is held in an arbor.

Then using a slitting saw, cut the two slots to tighten the screw up.

The screw tightens up without bottoming out the wedge, which is nice.

Next cut a little scrap of plate to width for the bearing locking dog. Mark the teeth on it...

... and file them to fit.

Last thing is to drill and countersink to accept the 4BA screw.

Now that this part is all together, it's quite fun to spin it around. Has anybody else studied double pendulums at some point? The motion is very reminiscent of them. Of course in use, the bottom pivot will be constrained to be the midpoint of the lever and won't spin around like this, but it's fun anyway.

Hours of amusement.

Hopefully I'll be able to start on the pivots next week.

You may have noticed that many of the fasteners on this bike use proprietry tools to tighten them up, there are lots of slots and holes etc. I've made a rough series of tools as I go along but at some point I'm going to have to make some decent tools to prevent damage to the slots. I have a cunning plan for this, more later.


In other news the long summer school holidays are drawing to an end. I like the school holidays because the traffic is so much lighter for my ride to work. In less than two weeks we'll be back to the usual mayhem. My lovely wife is running out of activities for the kids to do and they seem ready to go back to school. I had promised my son that we'd make a trebuchet over the holidays but I suspect it will have to wait. I also want to make a vortex cannon but that's going to really annoy the neighbours. I think I'll do it.

King Cnut - con rods part 3

What with Christmas and New Year and going away and having to make an appearance in the house every once in a while, it's only now that I can get back in the shed and continue work. I did manage a few solid days before Christmas though so I need to update you with the latest progress. I've got lots of photos to describe the steps to finish the con rods. Now then, where did we get to?

Mark the centre of the planet gear hole...

...and drill it out to enable me to...

...get the boring head into it and bore it to tears within 10 thou of size.

Then using a spiffy new adjustable reamer, take it out to the final dimension...

...which is a tight fit on the planet gear shaft.

Then without changing the set up, drill the hole for the locking wedge so that it just grazes the edge of the bore. 

This is the same locking mechanism as for the sun gear.

Then mill the hole into the bore.

Use your skill and judgement to work out what shape the wedge will be.

Then finish off the last part of the lap joints...

...and drill and tap them through.

Then using this new hole mount to the mill and create the top and bottom tapers.

Next round the end in the mill, with such a long handle I could manually feed this around.

Then mark out the shape of the end...

...and start to file the shape...

...until it's done.

Then take it all over to Kung Fu Pete's shed and borrow his gas set to braze them up.

Give the brazed joints a few minutes with a file.

Nearly there. Next machine the flats on the back of the planet mount for use with a puller when disassembling.

Then mill the slot for the planet bearing adjustment locking dog.

Finally, drill and tap the hole to hold the dog in place.

Oh yeah, drill and tap for the oilers and stamp the serial number on each one.

I told you there was a lot of photos.

Compare with the original con roads and you can see that the wedge has failed at some point and the owner has drilled through to use a pin to wedge the gear. This is one of the areas where the original bike has suffered at the hands of an excitable man with a large hammer.

Now that I have them finished, I'm aware that they seem very slender in profile even though they match the original. Conservative calculations on the yield strength of 4140 and the small cross sectional area indicate they are well able to stand my full weight but I'm not sure if the brazed joints will hold up to repeated stress cycles. Normal riding will be fine, but I worry about when I'm grinding away up hills and such like. I'll fit them and if they break, I'll make some more a little differently. As with so much on the bike, it's all a new learning experience for me. We'll just have to see.

Next shedweek I'll make the wedge and the planet bearing locking dog and possibly start on the pivots if my lovely wife can spare me from house duties.


In other news we have been away for Christmas, we usually do. We went up to the far north of the north of the North Island and very nice it was too. We skillfully managed to avoid the wet Christchurch weather and exchanged it for sub tropical humidity and heat. The whanau played in the sea while I went and poked around in a bloke's shed that he playfully liked to call a museum. Actually, it was quite good and I took the kids for a look, giving them a point for every exhibit they found that was also in my shed, my Dad's shed, Mr. Middleton's shed(s) or Kung Fu Pete's shed. I lost count but the game did cost me a round of ice creams.

My son doing his very best King Cnut impression, it was just as effective and he got hammered moments later. 

And you thought it was a typo, shame on you.