1932 Rolls-Royce 20/25HP Park Ward Saloon - barnfind project
Discussion
Hello all,
As a break from researching and writing about pre-war Bentleys, I thought I should update the Rolls-Royce 20/25 thread, as some more progress has been made!
This one is entitled Springs and Dampers!
Now, before we all get excited, this won't be the usual "I've bought some shiny new Ohlins and bespoke springs, which I will fit and it will be awesome" - type post. But then, I suspect, you guessed that and is probably why you are here reading this!
I have been successfully putting off the engine strip down for some months now, and this latest investigation into springs and dampers came about after a discussion with the purchaser of the front axle springs from my other Rolls-Royce - the 1929 20HP GLN76. He noted that the 20/25 springs looked rather crusty and all seized up. Well, as I am working on the "try to get everything unseized and work out if / how it needs repairing" principle, this seemed like a good prompt.
So, I set about cleaning up the springs and dampers and immediately realised that there was going to be more to this than originally expected.
The 20/25 uses Rolls-Royce's own design of lever arm hydraulic dampers for front and rear axle control, with the springing achieved with semi-elliptic springs mounted directly to the chassis. This design was miles away from my professional experiences of dampers and reminded me that, by 1932, hydraulic dampers were still in their relative infancy. While they had been available on top end cars since about 1925 or so, manufacturers were still only just getting to grips with the concepts of vehicle dynamics and ride comfort.
So, I set to work cleaning up the front dampers and comparing them to the handbook images....
It was clear that the previous owners had been less than careful - the filler plug thread was stripped and will need heli-coiling - and this "meddling" raised my suspicions about the damper valves. On stripping them down, they did not seem to match the drawings and bill of material sheets which you can access via the RREC archives. Had the PO disassembled them to clean - as is listed in the handbook instructions (Imagine that today - asking an owner to strip the damper valves down on your car!) - and then muddled them up or modified them? It was clear, when comparing left and right front dampers, that the valves, springs, spacers, washers etc were all a total state - and bore no relation to what they should have been!
Once I had got the damper valves apart, I was keen to understand how they worked. The dampers operate with a horizontal piston completely filled with oil. On the bump stroke, the oil is forced out of the piston into the reservoir. To improve ride comfort, the bump travel element of the piston has 2 valves fitted, each fitted with different pre-loads, which allow them to vent at "low" and "high" pressure. This gives greater control over the damper at a range of damper velocities and provides opportunity to tune the dampers for improved comfort. The rebound direction of the damper is un-valved and shows where the designers were concentrating their efforts.
The images show the drawings for the dampers and the valves and it became clear that the 20/25 dampers fitted to my car were, in fact, an upgrade over the original "launch spec" single valve dampers fitted to the 20/25, which had come across from the earlier 20HP. These new double valve dampers had come from the Rolls-Royce Phantom 2 rear axle and had been retuned for use on the front and rear axle of the 20/25. Some further digging in the "West Wittering" files - the archive of all the documentation created by Sir Henry Royce and his design team at West Wittering - showed that the company had been working hard to improve the suspension performance of both the Phantom 2 and the Small Horse Power range. Indeed, they had plans to create a new common vertical acting damper, which could then be used on both ranges of cars, but this did not progress as quickly as hoped. From the memos and drawings uncovered, it seems that Ernest Hives and Roy Robotham managed to persuade Royce that a more pragmatic solution was to use the dampers from the rear axle of the Phantom 2 on the 20/25, but retuned for the application. Thus economies of scale were achieved and bought them some time to get the new dampers to work.
For those who want to understand the full story - below are Sir Henry Royce's own words on the development of the dampers:
And, because I will always be an engineer, I have even been able to find some of the damper curves for the double acting damper which they were trialling. With a bit more work, I will be able to better understand the story. One thing which did make me smile was the recording of "ride comfort", measured by how much water got spilt from a container when placed in the car and then the car driven along rough roads. This is the direct ancestor of the ride comfort development work my colleagues and I did, and still do, at Bentley - but with much more modern technology!
For GBT47's front dampers, I have simply taken what I have found and tried to apply some logic. The valve caps and spacers are now the correct way round on both sides. I also found that the valve springs did not match the "E" low spring rate specification on the F57908 front damper drawing. This combination of spring and valve matches for D spec (normal or stiffer) road springs - so it seems to be a "valid" combination. This is now the same on both sides - before they were all muddled up between the valves.
Subjectively, with the springs now lubricated properly and the dampers full of oil, the control of the axle (when bumped up and down at different rates on axle stands) is more controlled. I have topped up the dampers with Penrite Shocker Oil No. 2 - an SAE20 oil designed for lever arm damper applications. There were some discrepancies across the various 20/25 handbooks on the type of oil required - often only listed by product name, not viscosity, but this was the one which seemed to fit best.
I also spoke at length with Andrew Baldwin at AB Classics (who advertise damper rebuilds in RREC club magazine Spirit & Speed) - he was very helpful. He does not provide a rebuild "kit" for dampers, instead making replacement gaskets, washers, spacers, as needed after cleaning. Sometimes parts need turning down to fit.
There are very few lever arm test rigs suitable for checking damper performance still in existence. The only ones he knows of (original R-R ones) are at P&A Wood. He said that there were 2 damper test rigs, one functional, one not, which he saw on a visit there. The dampers were tested in the machine which attaches a pen to the end of the damper arm and traces the output on a sheet of paper. The only other known possible damper test rig for RR dampers was made by Fiennes - this now may be with Alpine Eagle.
And, as yet, I can't get the rear dampers apart - the valve caps are seized, but I am hopeful that some soaking in oil and a bit of persuasion will do the trick!
So there we have it – the full springs and dampers run down (so far!) on the Rolls-Royce 20/25…. I hope you enjoyed it!
Take care,
AF
As a break from researching and writing about pre-war Bentleys, I thought I should update the Rolls-Royce 20/25 thread, as some more progress has been made!
This one is entitled Springs and Dampers!
Now, before we all get excited, this won't be the usual "I've bought some shiny new Ohlins and bespoke springs, which I will fit and it will be awesome" - type post. But then, I suspect, you guessed that and is probably why you are here reading this!
I have been successfully putting off the engine strip down for some months now, and this latest investigation into springs and dampers came about after a discussion with the purchaser of the front axle springs from my other Rolls-Royce - the 1929 20HP GLN76. He noted that the 20/25 springs looked rather crusty and all seized up. Well, as I am working on the "try to get everything unseized and work out if / how it needs repairing" principle, this seemed like a good prompt.
So, I set about cleaning up the springs and dampers and immediately realised that there was going to be more to this than originally expected.
The 20/25 uses Rolls-Royce's own design of lever arm hydraulic dampers for front and rear axle control, with the springing achieved with semi-elliptic springs mounted directly to the chassis. This design was miles away from my professional experiences of dampers and reminded me that, by 1932, hydraulic dampers were still in their relative infancy. While they had been available on top end cars since about 1925 or so, manufacturers were still only just getting to grips with the concepts of vehicle dynamics and ride comfort.
So, I set to work cleaning up the front dampers and comparing them to the handbook images....
It was clear that the previous owners had been less than careful - the filler plug thread was stripped and will need heli-coiling - and this "meddling" raised my suspicions about the damper valves. On stripping them down, they did not seem to match the drawings and bill of material sheets which you can access via the RREC archives. Had the PO disassembled them to clean - as is listed in the handbook instructions (Imagine that today - asking an owner to strip the damper valves down on your car!) - and then muddled them up or modified them? It was clear, when comparing left and right front dampers, that the valves, springs, spacers, washers etc were all a total state - and bore no relation to what they should have been!
Once I had got the damper valves apart, I was keen to understand how they worked. The dampers operate with a horizontal piston completely filled with oil. On the bump stroke, the oil is forced out of the piston into the reservoir. To improve ride comfort, the bump travel element of the piston has 2 valves fitted, each fitted with different pre-loads, which allow them to vent at "low" and "high" pressure. This gives greater control over the damper at a range of damper velocities and provides opportunity to tune the dampers for improved comfort. The rebound direction of the damper is un-valved and shows where the designers were concentrating their efforts.
The images show the drawings for the dampers and the valves and it became clear that the 20/25 dampers fitted to my car were, in fact, an upgrade over the original "launch spec" single valve dampers fitted to the 20/25, which had come across from the earlier 20HP. These new double valve dampers had come from the Rolls-Royce Phantom 2 rear axle and had been retuned for use on the front and rear axle of the 20/25. Some further digging in the "West Wittering" files - the archive of all the documentation created by Sir Henry Royce and his design team at West Wittering - showed that the company had been working hard to improve the suspension performance of both the Phantom 2 and the Small Horse Power range. Indeed, they had plans to create a new common vertical acting damper, which could then be used on both ranges of cars, but this did not progress as quickly as hoped. From the memos and drawings uncovered, it seems that Ernest Hives and Roy Robotham managed to persuade Royce that a more pragmatic solution was to use the dampers from the rear axle of the Phantom 2 on the 20/25, but retuned for the application. Thus economies of scale were achieved and bought them some time to get the new dampers to work.
For those who want to understand the full story - below are Sir Henry Royce's own words on the development of the dampers:
And, because I will always be an engineer, I have even been able to find some of the damper curves for the double acting damper which they were trialling. With a bit more work, I will be able to better understand the story. One thing which did make me smile was the recording of "ride comfort", measured by how much water got spilt from a container when placed in the car and then the car driven along rough roads. This is the direct ancestor of the ride comfort development work my colleagues and I did, and still do, at Bentley - but with much more modern technology!
For GBT47's front dampers, I have simply taken what I have found and tried to apply some logic. The valve caps and spacers are now the correct way round on both sides. I also found that the valve springs did not match the "E" low spring rate specification on the F57908 front damper drawing. This combination of spring and valve matches for D spec (normal or stiffer) road springs - so it seems to be a "valid" combination. This is now the same on both sides - before they were all muddled up between the valves.
Subjectively, with the springs now lubricated properly and the dampers full of oil, the control of the axle (when bumped up and down at different rates on axle stands) is more controlled. I have topped up the dampers with Penrite Shocker Oil No. 2 - an SAE20 oil designed for lever arm damper applications. There were some discrepancies across the various 20/25 handbooks on the type of oil required - often only listed by product name, not viscosity, but this was the one which seemed to fit best.
I also spoke at length with Andrew Baldwin at AB Classics (who advertise damper rebuilds in RREC club magazine Spirit & Speed) - he was very helpful. He does not provide a rebuild "kit" for dampers, instead making replacement gaskets, washers, spacers, as needed after cleaning. Sometimes parts need turning down to fit.
There are very few lever arm test rigs suitable for checking damper performance still in existence. The only ones he knows of (original R-R ones) are at P&A Wood. He said that there were 2 damper test rigs, one functional, one not, which he saw on a visit there. The dampers were tested in the machine which attaches a pen to the end of the damper arm and traces the output on a sheet of paper. The only other known possible damper test rig for RR dampers was made by Fiennes - this now may be with Alpine Eagle.
And, as yet, I can't get the rear dampers apart - the valve caps are seized, but I am hopeful that some soaking in oil and a bit of persuasion will do the trick!
So there we have it – the full springs and dampers run down (so far!) on the Rolls-Royce 20/25…. I hope you enjoyed it!
Take care,
AF
:-) Thank you!
There is a huge amount of data out there in the R-R (and Bentley) world! Combine lots of people who are very enthusiastic about the brands and the fortunate fact that both have (more or less) continued running without interuption (though Bentley's brankruptcy in 1931 meant that a lot of Cricklewood era information was lost) - this means that there is very little which can't be done or understood!
It's one of the things which I hope this thread shows - to anyone even remotely considering a pre-war Rolls-Royce or Bentley - do it! The knowledge is out there to look after them, the people are friendly, prices (for all but the rarest) have been softening over the last few years too. In a world of supercar-this and new EV-that, drive a pre-war Rolls-Royce or Bentley. Timeless, handmade luxury - much like the best mechanical watches or "proper" Northampton made shoes - they will never go out of fashion and will stand out for the right reasons. You'll be welcome anywhere and everyone will smile - not many cars will do that.
If not now...when?!
Sorry! Not sure where that all came from!
AF
There is a huge amount of data out there in the R-R (and Bentley) world! Combine lots of people who are very enthusiastic about the brands and the fortunate fact that both have (more or less) continued running without interuption (though Bentley's brankruptcy in 1931 meant that a lot of Cricklewood era information was lost) - this means that there is very little which can't be done or understood!
It's one of the things which I hope this thread shows - to anyone even remotely considering a pre-war Rolls-Royce or Bentley - do it! The knowledge is out there to look after them, the people are friendly, prices (for all but the rarest) have been softening over the last few years too. In a world of supercar-this and new EV-that, drive a pre-war Rolls-Royce or Bentley. Timeless, handmade luxury - much like the best mechanical watches or "proper" Northampton made shoes - they will never go out of fashion and will stand out for the right reasons. You'll be welcome anywhere and everyone will smile - not many cars will do that.
If not now...when?!
Sorry! Not sure where that all came from!
AF
andyfeaver said:
:-) Thank you!
There is a huge amount of data out there in the R-R (and Bentley) world! Combine lots of people who are very enthusiastic about the brands and the fortunate fact that both have (more or less) continued running without interuption (though Bentley's brankruptcy in 1931 meant that a lot of Cricklewood era information was lost) - this means that there is very little which can't be done or understood!
It's one of the things which I hope this thread shows - to anyone even remotely considering a pre-war Rolls-Royce or Bentley - do it! The knowledge is out there to look after them, the people are friendly, prices (for all but the rarest) have been softening over the last few years too. In a world of supercar-this and new EV-that, drive a pre-war Rolls-Royce or Bentley. Timeless, handmade luxury - much like the best mechanical watches or "proper" Northampton made shoes - they will never go out of fashion and will stand out for the right reasons. You'll be welcome anywhere and everyone will smile - not many cars will do that.
If not now...when?!
Sorry! Not sure where that all came from!
AF
Really enjoying this thread, so thanks for taking the time to update it. Particularly enjoyed the damper one. There is a huge amount of data out there in the R-R (and Bentley) world! Combine lots of people who are very enthusiastic about the brands and the fortunate fact that both have (more or less) continued running without interuption (though Bentley's brankruptcy in 1931 meant that a lot of Cricklewood era information was lost) - this means that there is very little which can't be done or understood!
It's one of the things which I hope this thread shows - to anyone even remotely considering a pre-war Rolls-Royce or Bentley - do it! The knowledge is out there to look after them, the people are friendly, prices (for all but the rarest) have been softening over the last few years too. In a world of supercar-this and new EV-that, drive a pre-war Rolls-Royce or Bentley. Timeless, handmade luxury - much like the best mechanical watches or "proper" Northampton made shoes - they will never go out of fashion and will stand out for the right reasons. You'll be welcome anywhere and everyone will smile - not many cars will do that.
If not now...when?!
Sorry! Not sure where that all came from!
AF
Just a slight correction - which is only relevant if you're writing about RRs as well as Bentleys.
It's either RR or Rolls-Royce. Never R-R. It's a hangover from Henry and Charles days. Still in the corporate style guide.
The great thing about these cars IS that they were hand-made. This means that, if you have the skills, most of the stuff can be remade.
With the exception of the casting, I think that I could remake everything in that hydraulic damper. I don't think I would be able to remake a modern damper, although I think I could find someone to refurbish it, but it would need a factory, not a shed.
With the exception of the casting, I think that I could remake everything in that hydraulic damper. I don't think I would be able to remake a modern damper, although I think I could find someone to refurbish it, but it would need a factory, not a shed.
Wow.
The deatil involved just goes to show the thinking of Royce and RR at the time. Excellence indeed...
I remember reading about the Derby era 30s cars, whose leaf sorings had their own oil feed, via tapered bolts
It really is F1 thinking and detail, but using 100 year old technology. And on a road car
The deatil involved just goes to show the thinking of Royce and RR at the time. Excellence indeed...
I remember reading about the Derby era 30s cars, whose leaf sorings had their own oil feed, via tapered bolts
It really is F1 thinking and detail, but using 100 year old technology. And on a road car
Hello all,
A small Christmas-time update on the 20/25 project. I must have been "good" this year, as I was lucky enough to be given a Dunlop No.10 jack, as needed to complete the first stage of the tool kit for my 20/25.
First - a little bit of history - the Dunlop No.10 jack was designed to work with the late Rolls-Royce Phantom 1 and early Phantom 2, as well as the 20/25. I am not aware that they were supplied for any other manufacturer or car (though I would be happy to be corrected!), so it makes finding them rather difficult. They do come up from time to time, so it was a bit of good fortune to get one this year.
I have spent a happy few hours cleaning up the jack and assessing to see if it is safe to be used as intended or whether it would be best left as a nice display piece. On stripping it down, there was clearly some wear on the gears, but it had been looked after as there was plenty of old grease - which has a very characteristic smell (the same from when I removed the rear hubs on the 20/25!?), and no serious corrosion.
Lots of degreaser, some WD40 and it was looking much better. I tidied up the teeth of the gears with a file to remove the worst of the burrs and then lubricated it with oil and modern grease, in the appropriate locations.
All that was then needed was a trial fit in where it will eventually be installed and it was a good result!
I have been kindly sent some images by a friend to show me how to fabricate the missing mounting bracket, to secure it to the chassis - but that will be a 2024 project!
Hope you enjoyed the little update.
Take care,
AF
A small Christmas-time update on the 20/25 project. I must have been "good" this year, as I was lucky enough to be given a Dunlop No.10 jack, as needed to complete the first stage of the tool kit for my 20/25.
First - a little bit of history - the Dunlop No.10 jack was designed to work with the late Rolls-Royce Phantom 1 and early Phantom 2, as well as the 20/25. I am not aware that they were supplied for any other manufacturer or car (though I would be happy to be corrected!), so it makes finding them rather difficult. They do come up from time to time, so it was a bit of good fortune to get one this year.
I have spent a happy few hours cleaning up the jack and assessing to see if it is safe to be used as intended or whether it would be best left as a nice display piece. On stripping it down, there was clearly some wear on the gears, but it had been looked after as there was plenty of old grease - which has a very characteristic smell (the same from when I removed the rear hubs on the 20/25!?), and no serious corrosion.
Lots of degreaser, some WD40 and it was looking much better. I tidied up the teeth of the gears with a file to remove the worst of the burrs and then lubricated it with oil and modern grease, in the appropriate locations.
All that was then needed was a trial fit in where it will eventually be installed and it was a good result!
I have been kindly sent some images by a friend to show me how to fabricate the missing mounting bracket, to secure it to the chassis - but that will be a 2024 project!
Hope you enjoyed the little update.
Take care,
AF
Edited by andyfeaver on Thursday 28th December 15:37
Hello all,
Am pleased you liked the Christmas update - I had hoped to share with you the rest of the rear damper rebuild story, but the parts I have had made still haven't arrived from the machine shop..... a follow up call in the morning required!
@ BrettMRC, bob1179 - good to have you along for the ride!
@ conanius - :-) I dread to think how many hours I have spent - but I have to say that both the hours and the cost are very much secondary to the enjoyment of doing it. I am certain that this project has had a very positive effect of my mental health and has been a wonderful way of learning about something which I have always admired! I have also been very lucky to meet some wonderful people who have amazing stories to tell... what's not to like for £5000?
AF
Am pleased you liked the Christmas update - I had hoped to share with you the rest of the rear damper rebuild story, but the parts I have had made still haven't arrived from the machine shop..... a follow up call in the morning required!
@ BrettMRC, bob1179 - good to have you along for the ride!
@ conanius - :-) I dread to think how many hours I have spent - but I have to say that both the hours and the cost are very much secondary to the enjoyment of doing it. I am certain that this project has had a very positive effect of my mental health and has been a wonderful way of learning about something which I have always admired! I have also been very lucky to meet some wonderful people who have amazing stories to tell... what's not to like for £5000?
AF
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