BSA Owners' Club Forum

Gallery - Best Selection Around => Which BSA do you ride? => Topic started by: corneg2 on 18 October, 2021, 20:26:12

Title: A10 plunger - new to this forum
Post by: corneg2 on 18 October, 2021, 20:26:12
Hello All. Finally got round to joining this forum. Did join the club years a go when I first got my bike, but let it lapse due to work distractions. Any way, mines a 1952 A10 - bought as a basket case about 14 years a go. I didn't do a perfect restoration - more a rebuild for regular use. This year I switched to 12v electronic ignition having previously been running the original ignition system. Best thing I have done to the bike, really transformed how she runs. Here are a few pics - hopefully. Cheers, Graham.

Title: Re: A10 plunger - new to this forum
Post by: Martin S on 21 October, 2021, 13:54:23
Completely off the original topic, can someone please explain how plunger suspension works? I've only ever owned bikes with swing arm suspension, so I have not had the opportunity to look at a plunger in detail.
Looking at the pictures of Graham's fine rebuild it looks to me that the rear wheel has a linear movement, constrained by the top and bottom spring. Is the resultant variable distance to the gearbox sprocket accommodated by the slack in the chain?
Does braking and acceleration cause added friction/binding in the plungers?
Is the principle similar to the Morgan sliding pillar front suspension? 
Title: Re: A10 plunger - new to this forum
Post by: idie on 21 October, 2021, 14:58:50
The chain slack will accommodate the suspension movement such as it is. Yes it does work like the Morgen front suspension but with far less movement. The problem can occur when wear sets in on the bushes then when you are cornering the wheel finds its own path.
Title: Re: A10 plunger - new to this forum
Post by: corneg2 on 22 October, 2021, 10:12:54
I can confirm that when riding a plunger vs a swing arm there is almost no noticeable difference. But Idie is right, if there is excessive wear then the rear end would feel a bit wobbly. A swing arm ensures that the wheel moves up and down in alignment on both sides, where as the plunger can have the wheel moving up and down sightly independently on each side - if that makes sense. But as I said at the beginning, if all components are in good shape then its all pretty tight and riding you can't feel much difference.

I don't know if its the same on a swing arm A10, but getting the rear wheel off a plunger is a piece of cake. The rear sprocket/brake assy stay connected to the bike when you remove the wheel, so no messing about with chains when you the need to remove the wheel.  ;D
Title: Re: A10 plunger - new to this forum
Post by: idie on 22 October, 2021, 11:50:45
Only on the earlier half width hub which is on splines like the plunger.