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Apr 16, 2023 - 3:14AM

Salty Bessie 2023 Speed Week

Thought I’d share an update on Salty Bessie, we had an eventful Speed Week at Lake Gairdner, South Australia. Subject to ratification (checks and balances and so on) we got the 350 APS VG record by the skin of our teeth, 90.040 mph average with previous record 89.473 mph. It was an eventful week, we got one run Monday at 13:45, but only 83.912 mph over mile 2, still accelerating to 84.412 on 3 1/4 mile. Clearly, we had the gearing too high. Track 2 was running shorter with no return road, so batches of runs were made with an escort back along the track. Around 15:00 on Monday we had some light rain, but then more overnight, much more, and we thought it was over for the year as we paddled in the saltwater Tuesday evening. But, by Wednesday we could get back on the lake to work on the bike (change rear sprocket and chain length to match) and Thursday after 10am rider/driver briefing racing re-started using Track 1, but not Track 2 which was still too wet and wasn’t going to dry. Track 1 start-line had been moved forward 200m to clear a boggy patch and would run as a short course until the afternoon when the 4-mile stretch would be dry. We waited patiently most of the day in the long line of bikes and cars at pre-stage, moving forward in groups of about 10 to be sent to the start-line, occasionally some bikes or cars coming by to run to the start-line to backup records. The track was scheduled to close at 6pm but in the afternoon it was announced it would stay open till 7pm. The dawn to dusk rules on access were being pushed to their limits.

We ran at 17:13, 90.318 mph over mile 3, which qualified for record backup. At first that would have been Friday morning but as I was checking and fixing up stuff in the impound, we were asked to get our kit on and get down to the start line! I got covered in salt spray on the run to the line and could hardly see, but Amanda (wife and the whole of our team crew) cleaned my visor and glasses off, with help from Tony (1228).There were other bikes and cars that I thought were ahead of me but then the starter called 1455 and it was my go, couldn’t get first gear to engage so after trying lots and just before Tony came to help, I just stabbed second and slipped the clutch to get off the line and was off, at 18:53, and got 89.762 mph over mile three, I was covered in salt when I picked up my timing slip. So, although the backup was slower it was just enough to back up and get the record, with an average of 90.040 mph against 89.424 mph current record.

As a recap and update of the bike. Frame is 1948 M20, actually an M21, engine is from my road M20, which is a girder model, the engine is somewhen for the war period. For this year I was running the original block, but bored for an 84mm custom forged piston, complete with ceramic topcoat and friction modifier skirt, WiseCo rings. Standard valves, I did a post in Feb on the frame of the sleeve for the big inlet block. I ran with Mikuni VM36 carby on an inlet manifold intended for a Triumph from MAP in the US, it’s 30mm at the port end, but this block hadn’t been opened up to match, so there was and is a nasty step that I just didn’t have time to address. Open pipe exhaust to just by the rear axle, with a wide band oxygen sensor and cylinder head temperature gauge as I’m now paranoid about overheating. With the gearing the RPM is above 5,500, maybe 5-10% because there will be some slip on the salt. Previously in 2021 we ran at the same speeds, a little higher, on lower gearing with a higher tail wind, 10mph vs 8mph. The higher revs were supported by the shorted exhaust, that cut off and exited to the right just before the kickstart. That setup wouldn’t run to full throttle with the higher compression head, a custom design that get to around 7.3:1. The ignition is around 31-32 degs full advance, maybe could have run more, but didn’t have time to experiment, and didn’t finish the homemade twin spark high-energy ignition either, so ran the original maggy with the dummy blanking dynamo, at least that meant that the 12V battery had plenty of power to run the AFR for the duration of the racing!

I’ve added a link to see photos and video. The video is both runs on the 23rd Mar, and then the runoff to the pits from Run 2, the backup run. At around 14s on Run 1 you can see the start of the timed 3rd mile, that’s larger sign to the far side of the track. The black markers are the ¼ mile markers. The end of the 3rd mile, with the 3, is around 50s. The ¼ mile markers are both sides of the track, so you can see when I pass the 3-mile marker when I pop-up from my crouch. Something else to improve, I need my head lower, which I hope to achieve with a small custom simple tank to get a few inches lower. Ideally I will also lower my bum, by extending the frame 6-8 inches to let the seat drop in before the rear wheel, but for that I need the front section of a broken chainstay as I’m not going to butcher the one I have for that purpose, and I don’t fancy making up all new to bend round the engine (hmmm, perhaps going under the engine would work though). The gearbox runs the close ration sleeve gear and matching fixed gear, ie a high third, so that there’s less jump at the vital last stretch to flat out in top!

https://1drv.ms/a/s!AmL8O4d7ahE7l5MjcXYZiN11ZZYwRQ

email (option): dickie.bobbie@hotmail.co.uk

Matty Leahy

Apr 16, 2023 - 4:03AM