BJ8 Tacho upgrade

Seriously thinking of getting my moving coil tacho. upgraded to a modern
stepper motor type movement, retaining the original face and case.
Speedy Cables in Wales offer this. There would be a minor linearity error with the existing scaling.
So, wondering (UK listers ?) if anyone has had this done and any comments about this type of conversion.

Are there perhaps any US companies that do this as well ?
Tkx
rg

" Are there perhaps any US companies that do this??

Ask Nisongner?

volts101 said:

Seriously thinking of getting my moving coil tacho. upgraded to a modern
stepper motor type movement, retaining the original face and case.
Speedy Cables in Wales offer this. There would be a minor linearity error with the existing scaling.
So, wondering (UK listers ?) if anyone has had this done and any comments about this type of conversion.

Are there perhaps any US companies that do this as well ?
Tkx
rg

Click to expand...

Im not sure what your upgrade is compared to what I just had done, but Nisonger here in the US upgraded mine to handle Pertronix and other electronic ignitions. The white wire loop behind the tach is no longer part of the tach function but there's a single white wire from the tach to attach to the coil for the pulse.

I have fitted an electronic 123 distributor and the tacho would not work any more I took it to a gauge rebuilder and his explanation was the electronics does not give out enough for the tacho to pick up. He then converted it by fitting a new board to the tacho this did away with the old coil system and from memory I had to run a new wire to the distributor/coil. The Australian cost was $150. The tacho works like a dream , no shakes, steady as, very responsive, could not be more pleased with the conversion. Saltiga

FWIW, my 'stock' tach works flawlessly with my Ignitor (Pertronix) ignition.

Bob_Spidell said:

FWIW, my 'stock' tach works flawlessly with my Ignitor (Pertronix) ignition.

Click to expand...

Mine originally did too but after I did a frame up restoration I noticed that it was reading low but would increase to correct rpm after driving for a while. Peter at Nisonger said that it was going out or wearing out. I made sure everything was hooked up correctly but it just would never read right after reinstalling in my car. The cutting out, going to zero, about 2700 rpm was also confusing.

I did have my dizzy rebuilt and switched to a top loader cap.

It has been my experience when the tach does not work with a 123 Dizzy I just add one more loop to the white wire and that seems to do it.
No problem with Pertronix.

In the UK John D Ostick does a conversion for modern electronic internals to go into any tach. I converted my BJ7 one. They can be positive or negative and be built to suit either points or electronic or both. JDO Instruments and he's quick.

https://jdo1.com

Keoke, I put in an extra loop, this did improve it to the point that it would flicker when the revs were up but nothing at idle. Saltiga

Recently went to Wales to collect my stepper motor converted tacho. and now installed.
So far very good; nice bright red ignition led indicator and led back lights.
They also changed the face text from “positive earth” to negative – nice touch.
Proper digital stepper motor (BTW Nisonger and others ? don't do this) so no more calibration or analog issues, or current pulses. No mechanical hairspring type movement.
Input is from from the CB on the coil and a new wire has to be installed; a little sensitive to routing. I use a Pertronix.
No doubt they could also convert mechanical tachos to digital as well.

Now digital speedos.

There are 2 options.

The first, that I have ordered, is to cut the speedo cable at a convenient spot and install a pulse transducer.
They are building me a RVI instrument that will be near identical to the original Smiths but with a LED display in place of the odo and trip.
This will have a modern digital stepper motor drive and hopefully stable and accurate. High beam indicator as before.
I have ordered this as MPH and so my plan, for driving in Canada will be to calibrate for 140 MPH as actually 140 kPH. This is easy to do and when in US will revert back to MPH. Only problem is that the total odo will be affected; may just use the trip to keep track or just stick with MPH
Will report back after receipt.

Second option is to use an electronic digital cable drive to drive the original magnetic speedo with odo and trip, if preserving the original look is important. This also uses the same pulse transducer as per the LCD one. The pulses now drive a mini digital brushless dc motor in a separate box. This box has a speedo cable output (usually short) so electronic scaling is easy but it is still a mechanical magnetic cup type drive. Hopefully, with no long cable the typical speedo blips etc will be eliminated. There is also some electronic filtering. This is the more expensive option and they insist they will only sell this option if you have the original speedo refurbished by them as well. This in the final stages of development and they have a large contract to fulfill in next 2 months, so realistically by Nov. time.

As I will still have my original speedo. so if not happy with the LCD above could resort to this solution.

rg