Author Topic: Plunger Columns  (Read 329 times)

Offline Russ

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Plunger Columns
« on: 06.02. 2020 10:41 »
My Plunger Columns, part # 89-4041 have a reasonable amount of chrome missing and are showing their age. My understanding is that they should be hard chromed. I have investigated having this done but the cost is prohibitive. I enquired at Draganfly, who have them in stock, however, was advised that they are not chromed at all and should be "smothered in grease".
Doesn't sound right to me. The bushes in the Plunger Tubes, which are simply steel ones, are worn but I can have new ones made.
Should the tubes be Hard Chromed? What do you make of the "smothered in grease" theory? Any suggestions of who can supply the correct ones? What clearance should there be in the bushes?
Thanks Russ


1951 A10 Plunger.
Australia

Online morris

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Re: Plunger Columns
« Reply #1 on: 06.02. 2020 12:16 »
Weird. Normally the columns (stanchions?) should be plain steel and the sliding bushes bronze. There should be a gease nipple on both wheel brackets to grease the bushes and columns/stanchions.
Maybe some PO modification?
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'52 BSA A 10 Plunger
'55 MORRIS ISIS
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Offline Swarfcut

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Re: Plunger Columns
« Reply #2 on: 06.02. 2020 13:50 »
  My '53 Model had plunger columns with what looked like a finish similar to the fork legs, which I do not think were hard chromed. Both parts had some kind of plated finish, the same as on gearbox layshafts and mainshafts. These always look too good to be just plain unfinished machined steel. Maybe they are hard chromed?

 My plunger columns had wear to this finish, so in true penny pinching style, simply cut another notch on the other side of the columns to match the pinch bolts and turned  them round so the worn areas were on the non-load side. Sliders had bronze bushes top and bottom, and space between them for lots of lovely grease. ( Early models, grease nipples stick out, later models they point to the rear).
 It was a long time ago......at a time when even pattern parts were rare and expensive.

 Some Hard Chromed Steel tube should do the job if you want to make your own. From memory it's 1" OD Tube.

  For all the marketing mens' enthusiasm, the Plunger system is at best flawed, and as long as the back wheel doesn't dance enough to scare you, don't worry. The sliders should be a nice sliding fit, with no chatter, slop or rattle. Damping is down to the mixture of grease &  dirt that accumulates and the inevitable less than perfect alignment of the rear frame section and its plunger columns.

 Better to substitute a steel tube for the top spring and make a Rigid Plunger. More predictable handling, so they say.

Swarfy.

Online Rex

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Re: Plunger Columns
« Reply #3 on: 06.02. 2020 16:55 »
My Star Twin's plunger columns were nicely finished but not hard chromed. Why would they be? BSA just machined the components to fit together nicely and be lubed by the mentioned dollop of grease. There were no pho-bronze bushes either, (unless my memory's playing up badly!)

Offline Russ

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Re: Plunger Columns
« Reply #4 on: 06.02. 2020 20:17 »
Thanks Guys, it looks like I was worrying about nothing. I will leave the columns as is and fit new bushes.
Cheers Russ
1951 A10 Plunger.
Australia

Online chaterlea25

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Re: Plunger Columns
« Reply #5 on: 06.02. 2020 20:28 »
Hi All
Hard chrome is quite a thick layer and I have never seen any of it peeling off even on old crapped out hydraulic rams
I wonder if Russ's plunger tubes were replaced with decorative chrome plated tubing ?
This would be a disaster waiting to happen  *eek*

John
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Offline trevinoz

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Re: Plunger Columns
« Reply #6 on: 06.02. 2020 21:53 »
I just had a look at my collection of columns, six in all, not counting two sets still in their frames.
All six have a chromed finish and I believe that they are original.
As they slide in steel bushes, it makes sense to have them hard chromed.
The bushes are definitely steel, I specifically checked.

Online ironhead

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Re: Plunger Columns
« Reply #7 on: 06.02. 2020 22:30 »
They need lots of grease to work properly. I give mine about 5 shots every 500 miles or so. When the excess starts finding its way out, wipe it off.
SA

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Re: Plunger Columns
« Reply #8 on: 07.02. 2020 06:10 »
They need lots of grease to work properly. I give mine about 5 shots every 500 miles or so. When the excess starts finding its way out, wipe it off.

Do your springs run inside outer cups so you can not see either the spring or shaft ?
It was papular down here to toss the cups and get the spring chromed as it was now exposed.
These were Sunday afternoon show off bike, not real riders.
Bike Beesa
Trevor

Online ironhead

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Re: Plunger Columns
« Reply #9 on: 07.02. 2020 09:51 »
All covers fitted.  Yeah if the covers arn't fitted they get covered in road goo but I suspect the uncovered ones don't get greased ( seize up ) so they look good on their once a month spin round the block.
SA

Offline trevinoz

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Re: Plunger Columns
« Reply #10 on: 08.02. 2020 21:20 »
Further to the bushes, I am pretty sure that they are cast iron, not steel.

Online ironhead

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Re: Plunger Columns
« Reply #11 on: 08.02. 2020 21:46 »
Further to the bushes, I am pretty sure that they are cast iron, not steel.


Cast iron makes sense, I've seen bronze fitted as well.
SA

Online Rex

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Re: Plunger Columns
« Reply #12 on: 08.02. 2020 21:48 »
Must be someone's repair then because BSA didn't fit any sort of replaceable bushes.

Offline trevinoz

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Re: Plunger Columns
« Reply #13 on: 08.02. 2020 21:53 »
The bushes are fitted to all of the tubes which I have and also to the ones that Russ has.
They are not listed as a separate part but are listed as tube and bushes. Part No 89-4046.

Online Rex

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Re: Plunger Columns
« Reply #14 on: 09.02. 2020 09:33 »
You're right. That'll teach me to rely on memory alone!