Monday, 17 February 2020

Nice Butt

This weekend I had to learn all about rainwater collection systems. You might have seen big green water butts standing innocently next to guttering downpipes. What I didn't know is that they're evil, and that they're biding their time until they try to knock your house down. I assumed that the guttering downpipe fed into the butt, and that it then had an overflow that fed into a second butt, or back into the guttering. I was wrong. The "diverter" that you let into the downpipe has a weir in it, and an airtight pipe to the water butt. Water can either flow into the butt, or over the weir and down the rest of the downpipe. There are a couple of reasons why this system is better than mine. The pipe to the downpipe can be small and flexible, if the flow down the downpipe overwhelms the capacity of the flexible hose, then the rest of the water just goes over the weir and down the rest of the downpipe.

It's a great system when everything is new. Now imagine that this water butt (which weighs 160kg when it's full) has been out in the garden for a few years and has been subject to hundreds of hour of UV degradation and dozens of frosts. Either the crappy plastic stand breaks and you don't replace it with something exactly the right height, or the flexible hose perishes. If the butt has been lowered by more than a few mm then the top of the butt is below the weir and all the rainwater flows down the side of the butt. If the flexible hose has perished the same thing happens. You are now collecting all the rain off your whole roof and funnelling it into one corner of your patio to try to undermine the foundations of your house.

I suspect that there's a better system where all the rainfall for an entire town is gathered together. It could be filtered and treated on an industrial scale until it's drinkable and doesn't bread lava and bacteria and then it could be piped back to individual households who use as much or little as they see fit - no matter how much or little rainwater their roof collects... Oh wait...

Richard "mains water" B

Tuesday, 11 February 2020

MOT

Last week my sports car failed its MOT. The fault was "Excessive play in rear suspension linkage. Look I can move this with my hand. This one isn't even done up Richard." I was told to take it home and re-torque all the fasteners in the rear suspension before I re-presented it. The rear suspension on a Caterham like mine is quite interesting and quite simple. There's a strong horizontal tube that has the wheels on it. It doesn't have the differential in it to save weight. The tube is kept in the middle of the car by a triangular A frame that is bolted to the middle of the tube and to the chassis well in front of the wheels. To stop the tube from moving forwards and backwards there are a pair of "radius arms" that are bolted to the ends of the tube, and to the chassis well in front of the wheels (like the swing arm on a motorbike). If I was richer the for/aft position of the tube would be maintained by 3 part Watts linkages giving almost perfect vertical travel.

What was interesting is that only the radius arms had loose fasteners, and it's only the radius arms that you have to take the seats out and get inside the car to work on them. Coincidence? Or something less? I wonder whether Caterham forgot to nip them up when they changed the differential.

Richard "anti-sabotage lacquer" B

Wednesday, 5 February 2020

Verb

Last week I witnessed the birth of a wonderful new verb. One of my colleagues had borrowed his girlfriend's car to get to work. When he bought a new car he had to drive his girlfriend's car home and then get his dad to pick him up and take him to his new car so that he could then use that to give his girlfriend a lift home so that eventually she would be re-united with her car and he would be in the same place as his new car. He said "I'm off to towers of Hanoi my new car".  Most of my readers are computer programmers so you're probably already thinking how perfect it is. If you're not familiar with it, the Towers of Hanoi is a little puzzle with three pegs and a stack of different sized disks. You have to move the stack of disks from one peg to another. The rules are that you move one disk at a time, and that you can never put a bigger disk on top of a smaller one.

Computer programmers have almost always studied it because it's a beautiful example of recursion. The recursive solution is:
1) Move all but the biggest disk onto the spare peg. 2) Move the biggest disk to the destination peg. 3) Put the rest of the stack on top of it.
In step 1 and 3 How do you move the "rest of the stack" – you're only allowed to move one disk at a time? Just follow steps 1) 2) and 3)

Yesterday a friend drove from his house to an MOT station so that he could pick ne up there and take me home, leaving my boring car at the MOT station. This morning, after pushing my scooter out of its way I drove my sports car to the MOT station so that I could leave it there and get in my boring car to get to work.

Richard "Bring on the self-driving cars" B

Sunday, 26 January 2020

Day Off

Most people take a day off work to go somewhere nice or to do something special. I took a day off work to spend it it my garage in the middle of winter making brackets that I would rather have bought.

I thought that I would like to be able to change the windscreen on my Caterham to a little aeroscreen. The car is low powered and it runs out of go on the straights. The windscreen is large and flat and stands almost upright. I believe changing to the aeroscreen should give me another 10mph top speed.

Getting to the fasteners on the windscreen stanchions involves taking a lot of the interior apart so I don't want to be doing that at a track day. I bought a pair of brackets that should provide captive nuts for the windscreen stanchions, but they didn't fit. I cut them up and fiddled about with some box section and some polyurethane adhesive and made these. They do fit accurately but they took me hours to produce.


This is the aeroscreen (it's still got the protective film on), a motorcycle mirror and a bracket that I made to join them together.


One of the questions that you never get asked in a social situation is "do you own a press brake?" although I wish you did. In my case the answer is "I don't know, does this count?". This is a very hard extension bar, my aluminium bracket, and a bit of soft wood in a very large vice.


Richard "I wish I'd never started" B

Wednesday, 22 January 2020

Gap

This week I share with you an old favourite family story. I don't know exactly when this happened but you can make a fair guess from the vehicles involved. My older brother had bent one of the half shafts on his Ford Capri and was fixing it in a hurry. He got a replacement from a scrapyard in Devonport. He got to and from the scrapyard as a pillion on his friend's Z750, on the way back he had the half shaft in his lap sticking out each side of the bike. They came back through the city centre and were very very nearly involved in a nasty accident. The rider went to cut between two queues of cars at high speed. While the gap was big enough for the bike it wasn't big enough for the half shaft of a Ford Capri. It became clear to my brother that the rider had forgotten about his passenger's cargo and that he was just about to be stuck off the back of the bike and probably have his pelvis shattered in the process. He let go with both hands and JUST managed to get the long, heavy, cumbersome shaft upright before they shot between the cars. Like some kind of incompetent post-apocalyptic knight with his rusty scrapyard lance.

Richard "retro" B

Tuesday, 14 January 2020

C125

This weekend I changed motorbike from a Yamaha TMAX (XP500) to a Honda Super Cub (C125). Obviously it's much smaller and slower, but I'm really pleased with it so far.

The clutch is automatic and the gearbox is upside down. I think you'd describe it as "One down, three down". It also has a Pacman door so that you can go round the back from 4th straight to neutral. As I've come from an automatic bike with a CVT I keep forgetting to put it into gear before I try to pull away. All my other motorbikes had the gearbox the right way up, so I quite often force it into the wrong gear during acceleration.

My least favourite change is the front brake. On the TMAX I had twin 4-pot callipers with high performance friction material and a 120mm front tyre. You could stand the bike on its nose with the pressure of two fingers and it felt like you could ruche up the tarmac in front of you if you wanted. It's not quite the same on the Super Cub. The mirrors are too close together and I've had to put one of them on an ugly extender. I also no longer get nodded at by bikers.

The fuel economy is absolutely outstanding, and the servicing costs should be low. It's fun to ride and it looks cute. The funniest features are an automatic clutch (so that delivery men have their left hand free to cold their cargo) and a heel pad on the gear lever (so that businessmen don't scuff up their smart shoes).

Richard "roll the power on gradually" B