Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[ooyah/2]

Derek,
I am sure that your area of expertise is in hydraulics so can you tell me if you know of any installation of hydraulics  where a ram operates at 3000 strokes per min with the fluid at 292deg F( Temp of  saturated steam at 45 psi.  3 bar )

Or a scenario where the stroke is 50% less at 1500 strokes per min with the same temperature of fluid.
Thanks
George

[ooyah/2]

   Difficult being a compound if all three bores are the same. Would suggest that MBH have "rollerised" the shafts to offer the normal bling market an alternative to the TVR. Do you really need needles at 3K RPM?  Sealing between pistons and bores if as quoted aren't going to do much for the compressed air fraternity.
 
  Regards  Ian.

Ian,
Your jacket is on a shaky peg, you've mentioned the dreaded word "B---G"  stand back for the slings and arrows.
George.

[derekwarner]

George.......
I have not mentioned nor suggested criteria such as "where a ram operates at 3000 strokes per min with the fluid at 292deg F( Temp of  saturated steam at 45 psi.  3 bar ",  but questioned a previous posting......."Smooth  piston without o-rings. The sealing between the piston and cylinder occurs when the motor is thermally ready to run through the expansion of the cylinder block. In this phase of preheating, the condensed steam can thus escape through the exhaust pipe"
We must also understand that a chemically treated aluminium component [cylinder bore] may have an abrasion resistance equating to that of Sapphire...however this may also be only 3 to 5 micron in depth...the substrate aluminium material is still raw aluminium and has the original low strength in resisting mechanical deformation [or toughness]...........
Through 35+ years in marine, military & industrial hydraulics, experience has taught me not rely on chemically hardened aluminium surfacing as a long term benefit ................
Derek

[Circlip]

But George, it does look sooooo pretty? 
 
  Hydraulic cylinders usually have flexible lip seals and the ends (both body and ram) mounted on pivots so that the operation is in a straight line rather that having side thrust. Even having oil as the filler, it didn't stop anodised components in a Citroen braking system from developing the sticky white sludge of corrosion.
 
  Regards Ian

[ooyah/2]

George.......
I have not mentioned nor suggested criteria such as "where a ram operates at 3000 strokes per min with the fluid at 292deg F( Temp of  saturated steam at 45 psi.  3 bar ",  but questioned a previous posting......."Smooth  piston without o-rings. The sealing between the piston and cylinder occurs when the motor is thermally ready to run through the expansion of the cylinder block. In this phase of preheating, the condensed steam can thus escape through the exhaust pipe"
We must also understand that a chemically treated aluminium component [cylinder bore] may have an abrasion resistance equating to that of Sapphire...however this may also be only 3 to 5 micron in depth...the substrate aluminium material is still raw aluminium and has the original low strength in resisting mechanical deformation [or toughness]...........
Through 35+ years in marine, military & industrial hydraulics, experience has taught me not rely on chemically hardened aluminium surfacing as a long term benefit ................
Derek

 Hi Derek,
 I know that you were not questioning the speed of operation but as my background isn't in Hydraulics I asked the question as I don't know how members can relate to full size Hydraulics in our range of model engines where heat is involved and especially those who have never built a " model " steam engine and just wanted to know if you have any knowledge of my question as the engine spec quotes 3000 rpm at 3 bar.
 
 I have built engines using Ali but only as the crank case and pumps from Ali but sleeved with bronze, cylinders and ringed pistons have been from Mehanite grade cast iron of 72 ton quality, poppet valves and seats machined from a Cummins diesel  engine exhaust valve to withstand the unknown temps and pressures involved.
 
 I am quite sure that Mr Baylis  with his many years of building and selling engines has a good idea of what he is up to, nevertheless there are some design issues with his engine on the mechanical bits, the materials for the cylinder and pistons is not the materials that I would have used but then it's only my opinion which I am quite sure will not concern him.

In your No 18 post you quite rightly point out the adjusting nuts on the piston and valve rods which to me indicate that graphite packing is used.
If a seal such as Silicone "O" rings were used there would be no adjustment as it would effect the groove dimensions for the "O" rings  and crush them.

Ian  has quoted the use of flexible seals on Hydraulic rams and bodies but can they be installed in such small sizes that we require, I doubt it, hence the use of Silicone "O" rings.

George.

[derekwarner]

Hullo George...& I hope I am not getting too far of track here...but must remind members of one fundamental point with old & new technology
We may only be generating steam @ 3 Bar [45PSI] ......but at 150 degrees C & virtually ZERO lubricity ....so we have eliminated the use of....Nitrile to ~~100 degrees C, ...H-NBR to ~~ 150 degrees C...HP & H-PU polyurethane elastomers to ~~ 100 degrees C
We are left with VITON [FPM], silicone & graphite which are suitable for the temperature but have poor strength & abrasion resistance or PTFE products which have no memory - [I have intentionally left out cast iron piston rings which have ZERO compatibility with chemically hardened aluminium surfaces]
I too am sure that young Mr Baylis has investigated the use of newer age materials & metallurgical processes....having said this...I agree that a 3D spheroidal grey engine cylinder barrel with BS1300 bronze piston will never cause a problem if correctly designed, machined & installed ...........Derek
 

[ooyah/2]

Hullo George...& I hope I am not getting too far of track here...but must remind members of one fundamental point with old & new technology
We may only be generating steam @ 3 Bar [45PSI] ......but at 150 degrees C & virtually ZERO lubricity ....so we have eliminated the use of....Nitrile to ~~100 degrees C, ...H-NBR to ~~ 150 degrees C...HP & H-PU polyurethane elastomers to ~~ 100 degrees C
We are left with VITON [FPM], silicone & graphite which are suitable for the temperature but have poor strength & abrasion resistance or PTFE products which have no memory - [I have intentionally left out cast iron piston rings which have ZERO compatibility with chemically hardened aluminium surfaces]
I too am sure that young Mr Baylis has investigated the use of newer age materials & metallurgical processes....having said this...I agree that a 3D spheroidal grey engine cylinder barrel with BS1300 bronze piston will never cause a problem if correctly designed, machined & installed ...........Derek

Hi Derek,
You are a little off track, all that I wish to know is if you know of any application where Hydraulic rams are operating at 3,000 stroke /min at 292 deg F, is it possible or not ?

George.

[derekwarner]

Well yes George.........& to answer you question is a little off track 
 
Rayathon [USA] designed CIWS [close in weapons systems] gatling guns that are capable of 4,500 rounds of 20 mm diameter projectiles per minute...as used on our HMAS FFG guided missile frigates
In a previous life I supervised the along side shore maintenance & occasional at sea trails of these weapons - they are electro/hydraulic in function....& yes up to 4,500 hydraulic actuator/cylinder component stroke pulsations were sequenced each minute
Your question of temperature @ 292 degrees F is irrelevant in this application...........Derek
 

[ooyah/2]

Well yes George.........& to answer you question is a little off track 
 
Rayathon [USA] designed CIWS [close in weapons systems] gatling guns that are capable of 4,500 rounds of 20 mm diameter projectiles per minute...as used on our HMAS FFG guided missile frigates
In a previous life I supervised the along side shore maintenance & occasional at sea trails of these weapons - they are electro/hydraulic in function....& yes up to 4,500 hydraulic actuator/cylinder component stroke pulsations were sequenced each minute
Your question of temperature @ 292 degrees F is irrelevant in this application...........Derek

 Thanks for that Derek,
 It's all a bit too testicle for me. I was thinking more of in an industrial application rather than military but I can't see how this would be a comparison to be used in model steam engine design.
 
 George.

[gondolier88]

On SY Gondola we have hydraulic application continuous sleeve packing. It cannot be removed or replaced in service, but it doesn't have to. They were installed 12 years ago, and with millions of revs chalked up, they are still in A1 condition.


The packing is a very very tight weave, multi-layered, fibrous (not sure what) graphite impregnated sleeve.


In service the sleeve is installed into a very close fit bore in the gland (I would suggest by the resistance at least +0.0015). The gland nut is put onto the piston rod, the rod pushed through the sleeve packing and the nut brought to bear on the sleeve. Next, you put two hands on the nut and tighten it as far as you can by hand- this is as tight as the nut goes, and no tighter.


After re-installing the engine this year, with a little oil put onto the sleeve before reassembly, they have gone back into service with zero-negligible blow-by.


The piston rods are hard chromed ground mild steel.


Derek, perhaps you could elaborate on what their original application may have been? Dimensions- 50mm L x 40mm ID x 6mm wall.


Greg

[frazer heslop]

Although I dont like the lack of a cross head. The cylinder may well be using seal-less principles
Either way I would rather buy a lathe and learn to build my own

[derekwarner]

Greg...as you suggest they may well be a woven material with graphite or PTFE infusions
There are many on the market depending on the pressure, temperature & surface speed...examples here range from 25 Bar @ 280 degrees C and 20/m per second to 450 Bar @ 550 degrees C
They are generally termed as older style, however totally robust & reliable...they are pressure energised....
Frazer........good luck with considering the purchase of a lathe....however stay away from seal-less principles.......   .....Derek

[frazer heslop]

Hi Derek, Iv owned a lathe and made model steam engines for more than 35 years its an addiction with me although I tend to build mainly hot air engines
The seal-less cylinders cannot be that difficult as even Mamod use this idea on there piston valve engines so I wonder if they have simply copied Mamods idea  as even by there own description of the cylinders workings it sounds very much like it
But I guess until I get my grubby hands on one for repair it will be mere supposition
cheers
 

[derekwarner]

opps......   didn't realize you were a [35 year+] engine builder Frazer.....
I have no knowledge of Mamod seal less pistons   ...but interestingly viewing a REGNER catalogue it would appear that their steam engines have synthetic moulded pistons which are in fact the piston body & seals in one moulding
With mass production, this in itself would be a very cost effective solution...the only downside I see is lubricity in a brass cylinder bore?????.............
With respect to the original posting......I am not sure where Giovanni sourced his information on the Baylis engine....... Derek
 
 

[frazer heslop]

Hi Derek, no problem I tend to be very shy 
It looks as if the toy makers are catching up with the real world I think the Regnor pistons may simply be that they are using a readily available piston moulding.It is a very good idea in  my humble opinion. I don't see a lubrication problem with those pistons they should be able to run dry ??? but without knowing the spec of the polymer its a guess
cheers
 

[gondolier88]

Hi Derek,


I knew I should have taken a photo of the sleeves when they were out! I see the packing you mean is basically a continuous ring of graphite valve packing, the sleeves I am talking about are, basically, a tube, rather than a square section ring. The tube being 50mm long, 6mm wall. I've asked a few people that should have known what they are, but didn't- I was holding out hope that you could have been the missing link to allow me to know what to look for to find spares- s**s law they'll need replacing next year after doing 12 years sterling service!


Greg