Bahne Bonniksen, a Danish horologist, used his considerable talent to create what we now know as vintage Bonniksen speedometers.
Bonniksen speedometers are highly sought-after as they are authentic and extremely pretty.
50mph Bonniksen speedometer in pieces. Credit Velobanjogent.com
Bahne Bonniksen (1835-1935) invented the “Karussel” mechanism in 1892. This made an enormous difference to the way that watch movements worked. He then offered the Bonniksen speedometer in 1912. Like the Karussel movement, the speedometer design was a considerable “upgrade” on the current offerings. It was considerably more accurate as it used a clock-type mechanism.
Prior to the Vintage Bonniksen Speedometers, they other mechanisms mostly used a governor-type of method. This involved weights being flung outwards as the speed increased. The Bonniksen design improved accuracy as they were less affected by vibration and wear.
The speedometer design came into the hands of Rotherham & Sons, of Coventry, ready for production in 1912. The 100 mph version was introduced in May 1925. Many Brough Superior’s had the 100 mph versions fitted.
The design of the vintage Bonniksen Speedometers
Bonniksen worked on the premise that speed is just Distance divided by Time. So, he designed a watch-type mechanism that measured distance by counting the number of revolutions according to the road speed.
Various design changes for vintage Bonniksen Speedometers for veteran motorcycles. (Image Credit Nick Smith)
He did this by using a gear wheel and gearbox (usually mounted on the front wheel hub) that had a cable attached to the gearbox and the speedometer. These vintage Bonniksen Speedometers used a balance wheel and escapement (used in watches of the time), to measure the distance by counting the number of revolutions of the speedometer cable. Bonniksen then utilised two hands on the face. These speed indicator hands took it in turns to display the speed.
They did this in 2.5 or 5 second intervals. In the initial designs, it was 5 second intervals. He changed this to 2.5 second intervals. When using one of these speedo’s, you will see each hand taking it in turns to indicate the current speed. One hand rests at “zero”, while the other hand displays the speed. After 2.5 seconds, they swap. The rest (zero) position is either 50 or 100 mph, depending on the speedo.
Vintage Bonniksen Speedometers were mainly offered in either 50 mph or 100 mph. I understand that they may have also been offered in kilometres. I have only ever seen MPH versions. If you have a Kms version, please let me know. Although the 50 / 100 mph versions would appear to only indicate up-to their respective speeds, they actually read much higher. They could read about 20% higher.
After the initial September 1912 – November 1913 design, Bahne Bonniksen produced a new variation. The new design was launched in December 1913 and incorporated a trip meter. This was displayed with two small dials in the face. Bonniksen did offer a speedometer without the trip dials for a lower price.
One of the dials indicated the trip miles with an ambitious maximum of 100 miles. The other dial showed time travelled in hours and minutes. A common design element from the onset, was the odometer. This indicated the total miles travelled, with a maximum of 9999.9 miles.
The gearing for vintage Bonniksen speedometers.
A speedometer isn’t much good as a head unit. It needs a way to receive the wheel revolutions. Bonniksen offered drive gearboxes for his speedometers. These were usually mounted on the lower portion of the front forks. The cable was attached to the gearbox output and connected to the speedometer head unit. There was a ring gear attached to the spokes / of the front wheel. In between was a pinion gear that connected with the ring gear and the cable-end.
The gearbox ratios were either 4.5-1 or 3-1. The Bonniksen head ratio is 500 turns = 1 mile. (Here’s where I rely of the enormously knowledgeable gentleman at velobanjogent, as my maths isn’t that great!). He states:
Using a Bonniksen speedo drive of 3-1 or 4.5-1 or a Smiths FW speedo drive of 1.5-1 you can work out the ring gear and pinion gear sizes you require, knowing that a 3.00x 21 tyre or similar turns approx. 750 times per mile. ( C=π.D…84.84 = 3.412x 27. Then 63360/84.84= 746.)
The ring gear/pinion gear combination has to reduce the 746 wheel turns per mile to the 500 cable turns per mile, taking into account the drive box ratio mentioned.
The finish was excellent. Nickel was the order of the day. So, the external drive gears, speedometer cases and gearboxes were plated in nickel.
These vintage Bonniksen Speedometers were available as an extra. They were not generally supplied as standard by motorcycle manufacturers. From around 1930, manufacturers realised that a speedometer as an excellent item to be supplied as standard.
Other old motorcycle speedometers
I have a few. Please see the current selection of motorcycle speedometers here. If you need a specific type, let me know.
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