An old Smiths ad for their right angle taco gearboxes and tachometers. These images were found on a Brit Bike Forum relating to a 1950's Matchless - link to the britbike discussion below:







http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=530395

Lots more Smiths right angle gearbox info here including very detailed dimensioned drawings:

http://velobanjogent.blogspot.co.uk/2009/09/smiths-tachometer-drive-gearboxes.html

Jeff.

Location: Almost but not quite, the far North East of England

Morning all

No reason to be sorry, honest. I am old but not a grump

I've gone to Ebay and the seller I got mine from is still selling. He must have gotten a pallet load at auction somewhere.

Here's the link

http://www.ebay.com/itm/Triumph-MG-Generator-w-Tach-Drive-NEW-LRD103-15027-15017-G4012-/171308859046?hash=item27e2cdbea6:g:-t4AAOxyBvZTVsbg&vxp=mtr

The goods are NOS. AND as such very nice. He will deal on price if toy buy a few, I did.

I own and restore a lot of old race cars and it's nice to just go to the shelf and get something that solves this problem

The drive itself is more robust than most of the older types ..... over the years I've had problems with the older style drives, i.e. Spridget and MG-T series style

If you want to build a tach drive distributor you need to fit the guts from a Lucas 40819 into the body of a 41241 if you can find any of this. Just an easy job if you can fond the two they come from Mini and GT-6 .... I've done that for so many years that the NOS distributors cost around US$20 each! But then I used to pay 1.5 UKP for a T-bone steak that didn't fit on the plate.

Location: Poland

Thanks Jeff, though my brain is starting to hurt with information overload!

If I have a 2:1 speedex rev counter with an anticlockwise dial, driven from the crank shaft which is spinning clockwise when looking on the end I think I need a reversing gearbox with a 1:2 ratio... now I seem to remember now why the meccano (other construction toys are available) reduction gearbox idea seemed a good one. I think I worked out that the 2:1 Triumph ratio would make the cable spin 4 times too quickly...

My head is spinning...

Bluto - fantastic, though again I'm wondering if the tach drive is 1:1 do I fit a pulley the same size as the v pulley on the cam... and which way will it spin?

Eureka!

I moved the dizzy to remove the spread of sparks caused by backlash - not because I really needed to, but just because it looked like fun to try. If I retain the original dynamo, I could fit a dummy dizzy (much reduced) and drive the rev counter from the back... I'm likely to need something to charge the battery anyway...

Since the generator is driven buy a pulley it's just a matter of measuring the cam pulley and picking a pulley to give you the ratio you want. I guess you could change the crank or cam pulley if you have a 4:1 for example.

Please remember being belt driven you can only consider the tach readings as suspect since it is driven by a belt Plesase keep the cable as straight as you can and bends gentle.

I have a couple cars I have fit with a small inline gearbox onto the back of the tach. One of our cars is fit with a Old airplane tach the only spare I could find was reverse direction of the one I use Went to the Speedo shop and got a little gearbox that reverses the cables rotation.

People forget that distributors are just made of metal and as such easily machined to suit.

Quick example:

I found a factory rev counter for a 1938 Packard. This was an export only item and NOS. So to make the drive I had a Mallory dual point for a Chevy V-8 w/tach drive. The Chevy unit rotates clockwise. Packard was a inline 6 and rotated anti-clockwise. I also had a Mallory for a 6 cylinder Ford rotates anti-clockwise. So I gutted the Chevy and fit the Ford parts to suit. This resulted in a 6 cylinder anti-clockwise tack drive dual point distributor. I machined the Chevy housing to fit the Packard. I only mentioned this to point out that nothing is impossible provided your determined and have the time. sometimes you must just put your hat on sideways.

Have you folks put a reversible drill motor on the tach to make sure there the cable and tach rotation are the same. I have a couple Tach with read out anti-clockwise but the cable turns clockwise .... these are internally reverse geared.

I have an old speedo/tach machine for adjusting and checking all this and a distributor machine also. After all these years they aren't used often but have saved me from real disaster

Waaaaaay East

Location: Poland

No doubt about the direction of rotation, they're nemag rev counters and there's not a gear in sight. (and thetefore also already subject to a degree of approximation!)

I rebuilt a dk4a with clockwise bob weights (thanks Dave) and slotted the holes in the action plate so it advances 8 degrees when spun clockwise, cut a new slot in the rotor cam so the clockwise rotor arm is angled correctly (anticlockwise when you look at it from above!)

I'm very low tech and happy not to spend money (not sure if it's a 7 trait or my Yorkshire birth) but parsimonious is my new middle name!

Location: Essex

Now where did I put that hacksaw?