Shimano derailleurs


Shimano Positron Preselect (PPS):

The first indexed gearing system to appear on a significant number of bikes – the first version in 1975 used two pull cables, the second in 1976 (this one) used a semi-rigid push-pull cable. The parallelogram is not spring-loaded, and is held in position by a spring-loaded ball on a notched arm.
The problem was that Shimano thought that indexing would only be for non-enthusiasts, so it was introduced as a cheap derailleur – the weight and build quality didn’t do it any favours, and it was dropped in 1982. Continue reading “Shimano derailleurs”

Suntour Derailleurs

Superbe Tech:

Probably Suntour’s most innovative and beautiful derailleur – and the company’s first glorious failure. The 1983 Tech has a completely enclosed linkage instead of the open parallelogram other mechs use. The cable routing was clever too – straight along the chainstay with no loops of cable.
That clever linkage would be the downfall, though – it wore and broke very quickly, and was very difficult to fix – so the Tech only lasted for a year.

Superbe Tech

Heinzmann control board

The Heinzmann controller board is a very sophisticated system – it’s basic features are:

It is a pulse-width controller, with very high efficiency.  There is a relay which overrides all the power, and is controlled by moth the on/off switch and a limit switch in the throttle for safety. The controller is specifically designed to prevent “spikes” – common with other controllers, which can damage the motor.

The controller is set with a ramp-up period of about 2 seconds – this is for the safety of the rider, and also to protect the motor from excess torque. The ramp-down period of the motor is zero – as soon as the throttle is turned off, then the motor stops.

The controller has a number of safety features: It continuously monitors the motor’s temperature, and cuts back on the power to prevent overheating. It also uses this to monitor the average power going to the motor. The controller also uses the “half voltage” from the cells to monitor the battery pack – if just one cell starts behaving erratically,t ehn the controller cuts back to prevent damage to other components.

Disabling the pedal sensor:

Some Heinzmann systems are supplied with a pedal sensor, which does not let you have any power unitl you pedal. It might be illegal where you are to disable this Cheap Pandora Outlet, but here’s how to do it if you really want to:

There are two types of controller board – the older style has an exposed relay, and standard microchips. The new type has a fully enclosed relay, and surface-mount chips.

Old type: the pedal sensor electronics are on a separate board, attached by three black wires. Simply snip those wires, and remove the entire subunit.

New type: this board looks like this:

This board has the pedal sensor electronics built onto the main board. To disable them, find the Zener diode on the lower left of the board. It’s NOT a surface-mount one. Snip out this diode (see above). That’s it!

Heinzmann Black Box

The Heinzmann Power Pack looks like this:

The box has three main components – the battery cells, the battery meter, and the control board. The control board is described in more detail elsewhere. The basic electrical arrangement is this:

The cells have a positive and negative from them, along with two (usually) wires from a pair of thermistors which measure the temperature of the cells, and an additional wire from half-way along the pack. This “half voltage” is used by the controller.

The negative goes to the battery meter, which is of the amp shunt type – it counts exactly how many amps flow in or out of the cells, so it is very accurate. The negative then goes on to the controller, via a 30A fuse. The positive goes straight to the controller, with a thin wire running to the battery meter to power the meter’s electronics.

Three wires from the charging socket go to the controller – but the controller is not involved in the charging process. The charger itself uses the thermocouples to monitor the temperature of the cells.

The Heinzmann motor

Looking inside the motor:

To open the motor, first remove the thin 17mm nut on the right side (rear motor: remove the spacer tube as well). Then unscrew the 6 cross-head screws around the perimeter of the shell on the left side. The motor should then slide out of the hub shell – you might need to give a gentle tap to the right axle. It will now look like this:

If you want to send the motor back to us, but don’t want to send the entire wheel, then this is a good stage to stop. If you want to carry on, then undo the 5 cross-head screws shown. These are the non-recessed screws – NOT the 4 recessed screws around the axle.
The gearbox will now open up – this is a tight press fit, so you will probably need to pry it gently with a flat-bladed screwdriver. Work around the gap, prying a little at a time, until it pops open. It’s easier if you have the motor axle in a vice to do this. It will now look like this:

As you can see, the motor has a small steel gear on it, which drives a larger spur gear. On the 200W motors, this spur gear is made of nylon to keep down the noise. This nylon is very durable, but after a lot of use it can wear – so check that the teeth look perfectly symmetrical, and that they’re all there of course! The high power motors have a steel spur gear, which never wears at all.

Going beyond this stage requires heavy machinery, so if your motor needs more than this, send it back to us. While you’ve got the motor open, clean out the old grease and pack in plenty of fresh grease. The reassemble:

Put the gearbox cover back in place – it may just push back on, or you might need to GENTLY tap it back with a rubber mallet. Make sure that the gears are meshing properly before you hit it too hard. Refit the 5 cross-head screws – note that three of them (usually) have washers, whereas the two outside the centre ring do not. Now slide the motor back into the shell – you might need to turn it about a bit to get the gears to mesh. Refit the 6 cross-head screws and the 17mm nut. NOTE: do not use any power screwdriver or similar on these screws – the alloy is quite soft and strips easily. Just tighten them with a standard hand screwdriver.

Motor fitting tricks:

The Heinzmann motor is usually pretty easy to fit to any frame or fork, but sometimes you’ll have a pair of (usually suspension) forks which will not spread far enough. If this happens, try replacing the thin 17mm nut on the right side with a washer – the washer must still be on the INSIDE of the dropout when you fit the wheel to the fork. If you still need more room, do the same on the left side – but be aware that the protective disc will be loose when you take the wheel off if you do this.

Brompton maintenance

General Maintenance:

The Brompton doesn’t need much in the way of maintenance – the sealed hub gears and galvanised chain make the gearing very durable. So, basically just oil the chain occasionally. Also oil the cables – especially, drip a little oil into the upturned end of the brake cable where it goes into the brakes at the front and back.

Adjusting the Gears:

The 3-speed SRAM hub gear (as fitted to all bikes from ~2001 onwards) is very easy to adjust:

  1. Unfold the bike completely – including the back wheel.
  2. Put the shifter into 3rd gear, and turn the pedals a few times to make sure the hub is in gear.
  3. Push the rod at the end of the toggle chain into the grey plastic fitting on the gear cable. Push it in far enough to remove all the slack in the cable, but not so much that the toggle chain has actually been pulled out a bit.
  4. Test ride the bike to make sure you’ve got it!

The 3-speed Sturmey Archer hub (fitted to older Bromptons) is almost as easy:

  1. Unfold the bike completely – including the back wheel.
  2. Put the shifter into 2nd gear, and turn the pedals a few times to make sure that the hub is in gear.
  3. Have a look at the toggle chain – try pulling it out. You’ll see that the chain is attached to a round rod, if you pull it out far enough.
  4. Tighten the barrel adjuster on the cable until the end of the round rod lines up exactly with the end of the hub axle. Make sure you’re lining up with the axle itself – not the wheelnut or the plastic pulley.
  5. Test ride the bike to make sure you’ve got it!

The 5-speed Sturmey Archer (also fitted to older Bromptons) is a bit more difficult:

  • Unfold the bike completely – including the back wheel.
  • Put the shifter into 2nd gear, and turn the pedals a few times to make sure that the hub is in gear.
  • Have a look at the toggle chain – try pulling it out. You’ll see that the chain is attached to a round rod, and on that rod is a little notch with red or blue paint in it.
  • Tighten the barrel adjuster on the cable until that coloured notch lines up exactly with the end of the hub axle. Make sure you’re lining up with the axle itself – not the wheelnut or the plastic pulley.
  • The 5-speed is more sensitive than the 3-speed – it can be fiddly to see what you’re doing, but try to get this as accurate as possible.
  • Test ride the bike to make sure you’ve got it!

The derailleur system on newer 6-speed bikes does not need any adjustment – it has a self-balancing system which makes up for any cable stretch. At least that’s the theory! If yours isn’t working, first check that the mechanism (especially that long spring) is clean and oiled. If it’s still not shifting cleanly, try opening up the shifter and moving the plastic cable stop one notch further up.

For some reason, on the P-types, Brompton often fit the 3-speed shifter wrongly – it should be fitted with the word “Brompton” completely horizontal, but it’s often fitted angled up a notch, which leads to the outer cable fraying. I always fix this on every Brompton I see.

Fixing a Puncture:

Front wheel punctures are easy on the Brompton, so I’ll concentrate on the back wheel:

  • Turn the bike upside-down – balancing it on the handlebars and saddle if you don’t have a stand.
  • Fold the back wheel over, to reduce the tension in the chain, and unhook the chain from the tensioner arm.
  • Fold the wheel back, and disconnect the hub gear.
  • Unscrew the toggle chain and pull off the toggle pulley (if there is one).
  • Use a 15mm spanner to remove the outer wheel nut and any washers.
  • Take off the chain tensioner – just pull it off the axle.
  • Use a 15mm spanner to undo the wheelnuts – undo them far enough to free the anti-rotation washers as well. Now you cna take the wheel off and repair the puncture.
  • To refit, first refit the wheel – don’t forget to loop the chain over the sprocket! Make sure the anti-rotation washers are in place, and tighten the wheelnuts.
  • Push the tensioner back on. The chain goes under the pulley.
  • Fold the back wheel over, and loop the chain over the tensioner arm pulley. Fold the wheel back.
  • Refit the outer wheel nut and any washers. If there’s a toggle pulley then make sure the tabbed washer lines up with the gear cable. You don’t need to tighten this nut too much.
  • Screw the toggle chain back in, and fit the toggle pulley (if there is one).
  • Adjust the gears as above.