Dubonnet Suspension
#1
Hello Everyone, I recently found a DY 12 from 1936, see Flutenews March 2019. Now I am desperately looking for any hint how to fix the worn out Dubonnet front suspension units. Maybe someone knows a specialist machine shop? Thank you very much for any Information,

Andreas (new kid on the block) Rolleyes
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#2
(20/04/2019, 08:27 PM)Andreas Wrote: Hello Everyone, I recently found a DY 12 from 1936, see Flutenews March 2019. Now I am desperately looking for any hint how to fix the worn out Dubonnet front suspension units. Maybe someone knows a specialist machine shop? Thank you very much for any Information,

Andreas (new kid on the block) Rolleyes

Hi Andreas - Recently took one of these apart and generally quite fixable though it is probably best to replace needle roller bearings with phospher bronze replacements.
Will look to see what I have tomorrow - What actually is your problem?
Regards
CB  <cbuk2011@aol.com>    Tel 01948880560
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#3
(20/04/2019, 08:27 PM)Andreas Wrote: Hello Everyone, I recently found a DY 12 from 1936, see Flutenews March 2019. Now I am desperately looking for any hint how to fix the worn out Dubonnet front suspension units. Maybe someone knows a specialist machine shop? Thank you very much for any Information,

Andreas (new kid on the block) Rolleyes


HI
"Shop manual" TS102/2 (or similar TS102/1 or oldiest HI 1938 manual) is the best help …. see "group L"; or "group 3"
I do not know what you are doing, but take care with "axle beam wedges" … they have correct position .
Send us photos for best help ...
Smile
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#4
(20/04/2019, 08:27 PM)Andreas Wrote: Hello Everyone, I recently found a DY 12 from 1936, see Flutenews March 2019. Now I am desperately looking for any hint how to fix the worn out Dubonnet front suspension units. Maybe someone knows a specialist machine shop? Thank you very much for any Information,

Andreas (new kid on the block) Rolleyes

Give me a ring to discuss your problems, there may be some easy fixes. I have 2 units but both require work
The H and I units are I think different than the Dx type Dubonney type.
Tel 01948880560
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#5
(20/04/2019, 08:27 PM)Andreas Wrote: Hello Everyone, I recently found a DY 12 from 1936, see Flutenews March 2019. Now I am desperately looking for any hint how to fix the worn out Dubonnet front suspension units. Maybe someone knows a specialist machine shop? Thank you very much for any Information,
Gentlemen,
I'm afraid there are no easy fixes for the Dubonnet suspensions!! 
Especially the D models

The use of bronze bushes would require a heavy lubrication oil.
Ds have an internal shock absorber within the spring assembly and these will only work with a hydraulic oil
Bronze bushes would create a very hard ride due to frictional loads, and the fact that the bushes would not last very long.
Plus (with heavy oil) the shock absorber assembly would not be able to function as the oil would not pass the valves at the correct rate and may even lock up (hydraulic lock) causing damage.

There are many scenario's with the use of a heavier oil to minimise oil leaks, one is, you might get away with using heavier oil and reduce the leak if you have worn internal shocks - but it will still leak!

As to the main cause of failure of the units in general;
The arm seal has always been the initial fault. 
This being mainly due to the type of rubber used and the fact that the arm side of the seal was usually running on a rougher surface than the bearing side of seal.
Oil leaked out and people did not bother with topping up (it's a bit of a pain) therefore subsequent needle bearings disintegrating. You only have to loose 1/4 pint (out of the 2 pint capacity) of oil to have the needle bearings running dry!

I have seen some of the 'quick fixes' and the damage caused.
If your bearings are worn - no matter what you try to do with the seal - it will leak!
Regards.
Chas.

A pessimist sees difficulty in every opportunity. A optimist sees opportunity in every difficulty.
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#6
(21/04/2019, 01:24 PM)Chas Wrote:
(20/04/2019, 08:27 PM)Andreas Wrote: Hello Everyone, I recently found a DY 12 from 1936, see Flutenews March 2019. Now I am desperately looking for any hint how to fix the worn out Dubonnet front suspension units. Maybe someone knows a specialist machine shop? Thank you very much for any Information,
Gentlemen,
I'm afraid there are no easy fixes for the Dubonnet suspensions!! 
Especially the D models

The use of bronze bushes would require a heavy lubrication oil.
Ds have an internal shock absorber within the spring assembly and these will only work with a hydraulic oil
Bronze bushes would create a very hard ride due to frictional loads, and the fact that the bushes would not last very long.
Plus (with heavy oil) the shock absorber assembly would not be able to function as the oil would not pass the valves at the correct rate and may even lock up (hydraulic lock) causing damage.

There are many scenario's with the use of a heavier oil to minimise oil leaks, one is, you might get away with using heavier oil and reduce the leak if you have worn internal shocks - but it will still leak!

As to the main cause of failure of the units in general;
The arm seal has always been the initial fault. 
This being mainly due to the type of rubber used and the fact that the arm side of the seal was usually running on a rougher surface than the bearing side of seal.
Oil leaked out and people did not bother with topping up (it's a bit of a pain) therefore subsequent needle bearings disintegrating. You only have to loose 1/4 pint (out of the 2 pint capacity) of oil to have the needle bearings running dry!

I have seen some of the 'quick fixes' and the damage caused.
If your bearings are worn - no matter what you try to do with the seal - it will leak!
I can;t say I agree, the early units had bronze bearings and you can use 20/50 engine oil in the units without causing any problems.
I have a unit in bits at the moment and they have quite a simple operation.
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#7
(21/04/2019, 04:12 PM)cbuk2011 Wrote: I can;t say I agree, the early units had bronze bearings and you can use 20/50 engine oil in the units without causing any problems.
I have a unit in bits at the moment and they have quite a simple operation.

I am not aware of the suspension being manufactured with bronze bushes - maybe you got hold of repaired units with bronze bushes fitted?

Have you disassembled the main spring and shock absorber?

A quick visual difference between early and late units was the filler.
Early units had the filler fitted just above the centre line of the arm shaft and later one had the filler fitted nearly on the top of the housing.
Regards.
Chas.

A pessimist sees difficulty in every opportunity. A optimist sees opportunity in every difficulty.
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#8
Personally I find that engine oil makes for too hard a ride, although I've only really experimented with these oils on the last development of the knee actions as supplied on the L model. With that knee action the damping action of the shock absorber is too hard using engine oil. However I would agree with Colin that it does provide better lubrication to the main arm.
I've tried the Penrite Shocker oil no.2 and it is better for the shock absorber action. So without further experimentation I used the No.2 Shocker oil on my DX Stratford Sports where I "need" a firm ride for good road holding.
I also tried the Penrite Shocker Oil No.1 and it gives a lovely gliding ride. It obviously works well with the shock absorber. So for cruising in comfort in a DX, J or LIP I use that thinner hydraulic oil in my knee actions.
I do wonder however about the lubrication of the main arm and whether the thin Shocker no.1 is sufficient as a lubricant, even though it is probably best for the shock absorber. So I've turned to the Penrite Shocker Oil no.2 for the bigger GY models where the lubrication is a higher priority.
I have had most of my knee actions rebuilt and the condition of that main bearing has been shocking in almost every case. Lubrication has not been reaching the main arm. As Chas says, previous owners have not kept the oil level up and with the powerful forces from that strong internal spring lubrication is essential.
Mike
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#9
D types were never fitted with phosphor bronze bearings for the wheel carrier arm. As Chas says if you find a unit with p/b bearings it's been got at!
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#10
(22/04/2019, 08:00 AM)Chris Knapman Wrote: D types were never fitted with phosphor bronze bearings for the wheel carrier arm. As Chas says if you find a unit with p/b bearings it's been got at!

Did you go for the tyres?
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