By Garry Simkin
Long the bane of air-cooled cars has been the starting of these things. In early days one relied on a couple of healthy pushers to get your beast up and running, but inevitably, just at the time that you needed that push, they had wandered off. Or they didn’t get up enough speed, didn’t understand about bringing the engine back onto compression, or just gave up. Towing wasn’t always an option given confined spaces, but sometimes a hill climb offered a downhill run to the start line which sufficed.
In the early 1990s when I resurrected my JBS Norton I figured that there had to be an easier way, so I cut up some square tube, fired up the TIG welder and got to work making a starting machine using two four-inch rollers and a hefty Nippon Denso starter motor. This worked well as I could start the car on my own so no assistance was needed. Others liked the idea and I ended up making about 15 of these devices. Whilst making life easier at race meetings some assistance was still needed to lower the ‘’hockey -stick ‘’ jack under the other wheel and get you off the rollers and on your way.
In time various people experimented successfully with onboard starter motors on the air-cooleds and in due course Terry Wright fashioned an automatic transmission flex plate onto his JAP twin drive sprocket and used a chassis mounted reduction starter on his Walton JAP. Brian Simpson made a similar arrangement for his Mk 9 Cooper JAP 1100 which works well. Fellow Mk9 Cooper Norton owner Grant Cowie then turned his hand to fitting a starter to his car, using a Harley Davison ring gear adapted to the Norton clutch sprocket which worked well and looks like this:
This inspired me to attempt the same thing with my Cooper Norton and a Harley 84 tooth ring gear was slimmed down and adapted to the NEB clutch (which we use here instead of the original Norton type – Ed) sprocket, and uses a modified Japanese car starter sitting above the gearbox. Adjustment with regard ring gear mesh had to be provided for when the gear box is moved fore and aft to alter chain tension. It looks like this in the car.
New ‘hockey stick’ shaped plates running from the ‘’triangle’’ at the back axle and connecting the top of the Norton box and on to the chassis had to be profile cut and modified to hold it all together. A lot of work for sure but one push on the starter button has it running, and once again no outside assistance is needed.
The motor is a 1.5kW reduction unit from CAE Performance Products in Chewton, Victoria and can be seen running on our Facebook page as we haven’t worked out how to embed it here.
Grant Cowie is running a light weight on-board battery with an isolator switch, but at this stage I will opt for using an Anderson jump plug and remote battery to fire it all up. An aluminium cover over the starter pretty well hides it. Its a lot of work, but as we get older we need to make life easier for ourselves. GS.
Loose Fillings editor Terry Wright adds some notes on his experience…
My approach only a few years back was a little different to Garry’s which has the starter motor cleverly mounted above the gearbox and driving the clutch assembly. For the Walton-JAP, with a new-build 1270cc reproduction of the 8/80 JAP Bruce first had in the car, I chose to drive the engine mainshaft from a forward-mounted motor on the mountings that once housed a supercharger. I made up a double main sprocket using a ‘flexplate’ from a little Daihatsu which was screwed to the drive sprocket on the mainshaft with a suitable spacer. The starter motor supplier Hi-Torque in Victoria provided a gear on the motor to suit the teeth on the flexplate. Installed it looks like this:
Knowing no better, I picked the biggest race car starter motor in the store, which was sufficient to start a V8 race motor. Almost certainly this was overkill and unnecessarily heavy, but boy, did it go! It went so well that I wondered if it was responsible for my first attempt at a pressed-up flywheel assembly shifting fractionally. Everyone I consulted said ‘no way’. Not being entirely convinced I collaborated with engine-builder Greg Summerton in South Australia and engineer Roald Pedersen in Norway who had access to some modelling software to do various calculations and the tentative conclusions were that everything was alright.
The above jumble of engine stuff is masked as below by a cowling in the same shape as the fuel saddle tanks that Bruce Walton used.
The new pressed-up crankshaft that Greg made has shown no sign of shifting under the starter load and is smooth as silk in operation. Garry says he has found no need to retard his ignition for starting but with the programmable Harley Davidson ignition I adapted to the JAP I was able to set the ignition advance to zero for rpm up to 500.
For the record, the motor I used was rated at 2.5hp or 1.9kW. So I can say with certainty that a 1.9kW starter is fine with a big-twin and 1.5kW works on a Norton or other single cylinder engine as Garry has been using. Note though that Garry is driving his crankshaft via the primary chain so think about how this change of gearing gearing. Whether the weight and cost savings of a smaller motor would be satisfactory remains to be established. Maybe someone would like to have a go and let us know?