Series 'A' Twin Magneto Drive Sprockets

[A_HRD]

Bill,
I can virtually guarantee that HPC Gears in UK will have sprocket blanks to suit the A Twin Mag Drive - and a chain too if required. I even purchased from them a length of pre-formed blank from which I parted-off new Series 'A' oil pump gears in EN202 .

I guess the issue will be postage delays to NZ - unless you can find a VOC Brit heading in that direction soon.....? https://www.hpcgears.com

Peter B
Half 'A' Section Organiser

 

[billirwinnz]

Hi Peter

I have found some blanks locally which I can machine down. Cheap too! I’ve already made a new chain loop from a bit of high tensile bicycle chain.

Cheers Bill

 

[A_HRD]

Hi Bill,
The HPC blanks have a boss on the side too - which you can machine (or machine-off) according to your needs. Yep, the hi-tensile bicycle chain will do just fine; but I would change it every 5K miles - perhaps less...(?) - just to be on the safe side.
Peter B

 

[billirwinnz]

Maughans have them but at 69 pounds each plus postage and import VAT I think I'll go with machining local blanks at 5 quid each.

 

[billirwinnz]

Hi Bill,
The HPC blanks have a boss on the side too - which you can machine (or machine-off) according to your needs. Yep, the hi-tensile bicycle chain will do just fine; but I would change it every 5K miles - perhaps less...(?) - just to be on the safe side.
Peter B

Hi Peter
Why would you replace the chain at such a low mileage? My electric bicycle produces 96Nm of torque transmitted through such a chain. The torque needed to spin a magdyno must be tiny in comparison. But I guess it is turning over many times faster.
Bill

 

[billirwinnz]

The existing chain uses homemade 1/8" sprockets and rollers hence the bicycle chain but the blanks I have ordered use standard 08B chain and there is room for it so I will switch to that rather than grind down the blanks. Is it what was used originally?

 

[A_HRD]

Hi Bill,

Perhaps I am being a bit pessimistic about chain life; I have reason to be given my trashed triplex at speed on my C Rap - and years before, coming off my AJS7R - also at speed (primary snapped and locked-up the whole plot!). Bumps, bruises and Radius/Ulna bones poking through my leathers...

At least changing the mag-drive chain on the A Twin is a simple exercise.

Unfortunately, I have no way of knowing which brand/strength of chain was originally fitted in the 1930s; suffice to say one hopes it was the best available at the time! Sure, use 08B - that's what I'll be going for. But I'll be checking it at 5K miles.

Peter B

 

[billirwinnz]

Hi Peter
Now I understand the source of your caution! I've fitted new triplex chains to the four twins I have owned over the years because I wanted to be certain that they were good ones. At 40,000 miles on my current bike it's probably time to replace it again although it hasn't needed much adjustment. I've done 20,000 on the xring rear chain and only had to adjust it twice which is a huge contrast to the old chains which needed frequent adjustment and only lasted 4-5000 miles.
Bill

 

[Chris Launders]

I am very puzzled by the number of triplex primary chains that seem to have broken, it doesn't seem to occur on anything else, could this be a result of the ESA not being up to the job, in fact adding shock loads to the chain.

 

[timetraveller]

Triplex chains were not know to break frequently many years ago. I wonder if someone has been supplying some indistrial grade chain?