Propshaft Upgrade ?

Servicing, Repairs & Restoration for your Austins.
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martyngriff
Posts: 5
Joined: Thu Feb 02, 2017 6:13 pm

Propshaft Upgrade ?

Post by martyngriff » Sun Feb 05, 2017 9:02 pm

I have a 1928 12/4 Burnham saloon which I have had for many years but anything above 30 MPH it shakes a lot, there is a vibration period just above 30 which if you are brave enough to push her through goes a little less above 35, I have seen 40 but not very often. She is a great car apart from this issue. The engine was reconditioned and is in excellent condition, she runs very smoothly, but I have been contemplating changing the prop from the original to a sliding U/J jointed one. There is a company near me that makes up props which would do the job, has anybody any experience of changing props on 12/4's to modern props with sliding joints and U/J's ? Does anyone on the forum think this would held the issue ? Thanks Martyn Southport

Arabella_12
Posts: 9
Joined: Tue Dec 27, 2016 2:25 pm

Re: Propshaft Upgrade ?

Post by Arabella_12 » Mon Feb 06, 2017 7:47 pm

All 12/4s seem to have a vibration period - usually up in the high 30s - but I think that's engine related. I delved into this because I had a horribly vibratory engine - but I established by coasting etc that it was NOT the transmission, which yours seems to be. Mine was internal horrors in the engine - a story for another time.

Simplest thing to check first, I'd suggest, is the fabric coupling 'UJ' on the back of the gearbox. New ones are available from the club, if yours has got all the layers of canvas coming apart, allowing the propshaft to slop around and get out of balance, which would give the symptoms you describe. (?Or even just loose bolts onto the fabric coupling). Fitting a new one is fairly self-explanatory; I think you have to drop the shaft off the rear axle first, to make enough room to separate things at the front.

The rear UJ is a strange thing to my eyes, but fairly simple, and should be easy to inspect or wobble, to see if it is seriously worn. But another thought springs to mind: are the rear engine mounting bolts tight on the chassis?

Sorry if I'm stating the blindly obvious - but these are cheaper and quicker fixes than converting U-Js, rebalancing propshaft, etc, so maybe worth checking first. Good luck!

Mike01
Posts: 19
Joined: Sat May 14, 2016 9:27 am

Re: Propshaft Upgrade ?

Post by Mike01 » Mon Feb 13, 2017 11:50 pm

Have you looked at the fabric coupling? or the sliding blocks at the back end of the prop shaft. These can wear, but I must say I have had them nearly dropping off and still no vibration. Have you looked at the wheels or track rod ends. A damaged wheel or a worn track rod can induce vibration, its worth a look.
I think its a bit drastic and expensive to fit a new type of prop shaft before exploring the other possibilities.

I suggest you contact Tony Smallbone. Tony is very experienced with 12s and I am sure he will come up with a solution for you.

Tony's email and phone are.
tonysmallbone46@btinternet.com 0121 472 7139 day only.

Mike Egg

martyngriff
Posts: 5
Joined: Thu Feb 02, 2017 6:13 pm

Re: Propshaft Upgrade ?

Post by martyngriff » Sat Feb 18, 2017 12:28 pm

Mike & Arabella, many thanks for your comments, I will check these things out, it's like a lot of things it's a job I need to get round to doing and other vehicles seem to have crept in at the sides demanding time ! I will look over the things your suggest and re-post when I have done these. I have a ramp which makes things easier so checking things out should be easy, I am pretty sure the fabric joint is the original one which must have been put on when the car was restored in the late 80's. I will nip it out and see, I also should be able to jack the wheels up and run her on the ramp to see how the prop runs, that should give me a clue as to what is going on. Cheers Martyn

Hillstart
Posts: 1
Joined: Thu Jun 14, 2018 1:21 pm

Re: Propshaft Upgrade ?

Post by Hillstart » Sun Jul 15, 2018 10:59 am

Hi
I have a Burnham 16/6 bught it in Feb 2018, one of the first things I done was having a new prop shaft made up, sliding joint and 2 UJ's cost $1000 AU Now it's a smooth ride up to 45/50 mph (I will add that I found 1 loose bolt on the front coupling)
Its a bit of a fiddle as the front flange has only has 3 bolts, I used Cap head bolts, UJ's are better than the brass blocks at the diff
they don't need much play in to be out of balance.

martyngriff
Posts: 5
Joined: Thu Feb 02, 2017 6:13 pm

Re: Propshaft Upgrade ?

Post by martyngriff » Fri Jan 11, 2019 1:49 pm

Hi most interesting, do you have any photos of the prop ? Thanks Martyn

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