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 Post subject: Building Reeves' Commander engine
PostPosted: Wed Nov 18, 2009 5:15 pm 
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Anne from Little Britan
Anne from Little Britan
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Joined: Tue Nov 17, 2009 11:17 pm
Posts: 232
Location: Roseville, MN
Posted on behalf of Roger Eske:

Roger Eske
Just Starting Out


Joined: 09 Oct 2007
Posts: 5

Posted: Sun Feb 15, 2009 8:06 am Post subject: Building Reeves' Commander engine
Afternoon - not sure if already put this on "technical" haven't been active
on SBA site before - but will repeat just in case.

Am in the process of building a Reeves Commander steam engine (eventually to go into a steram launch) and am at the point where the
quadrant has to be notched to receive the reversing lever latch.
Have found there is only 31 degrees of movement from left to right.
This is controlled by the expansion links. Reeves' drawing of the quadrant
indicates something like 45 degrees total movement but does not state
such. Notes on the detail drg. instruct you to mark off on assy. I have triple checked the parts to drgs and find no errors. Has any member
built the Commander and have knowledge of this condition? Does any
member have details fo the valve geometry. Obviousl would welcome any input.
Hopefully can pick up any reply on this site - otherwise e mail is:
sueeske@talktalk.net
If telephone discussion helpful would be delighted to ring from here
to save any telephone costs your end.
Yours hopefully
Roger Eske
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Edward
Lighting the Boiler


Joined: 01 Oct 2007
Posts: 39
Location: Ambleside, Cumbria, UK
Posted: Sun Feb 15, 2009 12:46 pm Post subject:
Dear Roger ,
I hope I'm not going to put too much of a damper onto your dreams but as far as I know no one has ever managed to get a Commander to run reliably while doing any worthwhile work .
I'm not an engineer and don't know the technical details about this other than having been told that it is a fundamental design flaw.
Alan Howarth spent several years trying to get his to work satisfactorily in his boat Lady Marguerita but eventually had to admit defeat though I believe he did get reasonable results running it as a simple .
I don't know if the problem is related to the situation you describe but Alan is a member of the SBA and I dont think he would mind if you gave him a telephone call to talk about it .
Sorry I can't give any more optimistic advice or information.

Edward .
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Maltelec
Site Admin


Joined: 23 Sep 2007
Posts: 156
Location: Cumbria, UK
Posted: Mon Feb 16, 2009 2:11 am Post subject:
One comment I remember someone saying was that the engine is more of a glorified model than a real working engine, and as such everything is too small on it, especially the eccentric rods.

Now not knowing the engine myself other than seing one 6 years ago I can't offer my own opinion on what areas are in need of a rethink.
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I've got the vehicle , just need the boat.
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marinesteam
Lighting the Boiler


Joined: 28 Nov 2007
Posts: 39
Location: Colorado, USA
Posted: Mon Feb 16, 2009 6:54 pm Post subject:
Roger,

Can you provide a better description of the valve mechanism on your engine.
I have never seen a Reeves Commander engine so I can only surmise what may be the issue, but here it goes.

It doesn't sound like there is anything out of the ordinary if you have a Stephenson link and drag rods.

There will be a difference in angular travel of the reverser lever and the link depending on the length of the arm that moves the drag rods (I think it's called the weighshaft lever).

The plans for the York engine also call out to have the quadrant notches cut at assembly. There is much potential for tolerance build up in this mechanism. It really is the best way to ensure optimum alignment of the eccentric rods and the valve stem when in full gear.

I'll be posting CAD pic of the York engine later tonight as I need to get a sanity check before correcting some apparent discrepancies in the prints for that engine. Maybe these will help in finding a solution for your issues as well.

Later

Ken
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Roger Eske
Just Starting Out


Joined: 09 Oct 2007
Posts: 5

Posted: Tue Feb 17, 2009 7:46 am Post subject: Replies re my "help" for building Reeves Commande
Afternoon - Edward - thanks yr comments - ah well !
Will contact Alan as suggested - at least he can tell me the worst

Also ref Maltelec - joined 23 Sep 07 - well I like a challenge



Ken - Colerado USA
Isn't the world a small place sometimes !!
Thanks yr comments - very useful interesting what you say about the tolerance etc.
Await yr CAD pic later - sounds as though the York engine prints might
have a similar problem to the Commander.
Think you might well be able to offer some advice here anyway-
Will await the pic with great interest and will come back with further
technical details of valve mechanism etc.
Thanks again for coming back
Roger

P.s. if you prefer you can contact me directly via e mail -
which is sueeske@talktalk.ent
Await yr further news
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Roger Eske
Just Starting Out


Joined: 09 Oct 2007
Posts: 5

Posted: Thu Feb 19, 2009 9:42 am Post subject: York engine CAD print
Ken - Colerado -

York engine CAD print and details well received - many thanks.
There do appear to be certainly some basic differences -
Am putting together more details of Commander valve geometry and
will send them - hopefully tomorrow - to see if you can sort me out!!


Many thanks Rog' Eske
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Roger Eske
Just Starting Out


Joined: 09 Oct 2007
Posts: 5

Posted: Sat Feb 21, 2009 5:16 am Post subject: Building Commander
Morning Ken in Colerado -

Many thanks for your help and contact-
From a telecon with "Steamboat Jack", it seems there some inherent faults in the
design of the Commander. As yet I have not spoken to anyone rumming that engine - but I intend to, to ascertain the direction in which to go i.e. onward-onward or back to the drawing board.

Many thanks for responding and help. I will keep you posted. Have you noticed how tears rust steel !!

Best regards Rog'
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steamboatjack
Urchin


Joined: 01 Oct 2007
Posts: 39

Posted: Sun Feb 22, 2009 6:15 am Post subject:
Roger,

I have studied the general arrangement drawing and below are a few notes on this, however without detailed drawings I cannot go much further other than offering an few alternatives as detailed. I will mail you dimensions etc. when I am not quite so busy. I will copy this e-mail onto the forum so as to benefit others.

1 cylinder bore ratio, 50,75mm is 1.5:1 or 2.25:1 by volume.
engines running condensing should generally have a higher ratio than this depending on the supplied steam pressure. about 3.5:1 at 100PSI to 4:1 at 150PSI by volume in other words the L.P. should be getting on for twice the diameter of the H.P. in this case there is very little can be done here, I know of at least one engine built as a twin H.P. presumably by fitting liner(s). With this size of engine, a twin H.P. is in fact a better bet as the condensation loses in the cylinder would probably negate any saving in steam as a compound, but as the engine already has air pumps its worth a try as a compound.

2 Rotation. as drawn the crosshead arrangement is suitable for a clockwise rotation being the ahead direction.This means as drawn a "left hand" propeller would be needed instead of the usual. The cylinder block maybe fitted the other way around? I cannot tell from the drawing.

3 length of connecting rods. The connecting rods (and subsequently the eccentric rods) are too short. The minimum length of the conn. rod should be 2.25x the stroke as a minimum, 2.5x is better. they appear to be about 2x (120mm) these items greatly effect the valve gear function.

4 The valve gear arrangement. As drawn the gear has "open rods" but the ahead direction (as 2 above) uses the eccentric on the left of centre which is furthest from the drag link (lifting link on a loco) pivot. It is normal practice to have the ahead eccentric nearest to this pin when using this kind of link. With the links central as drawn the drag link should be near horizontal and the reversing arm vertical (exact details later). The imaginary horizontal length between the valve spindle pin from ahead to astern should be three times the valve total travel about 69mm whereas its about 48?
It would appear that the designer has put the wayshaft in a position which suits a neat reversing lever and quadrant without any thought to its proper function. Should this valve gear operate at all it would be due to luck rather than correct design.

5 Other problems. There maybe other problems in this design, the crosshead and pin arrangement is a usual spot for poor design but this cannot be checked without further data.

remedies.

2. should the engine be run anticlockwise (as drawn) the side thrust will be mainly on the guide retaining strips rather than the casting. ok for running astern but just plain "wrong" for running ahead.

3. The engine could be fitted with packers under the crosshead guide castings and lengthened front columns, new connecting rods (150mm) and eccentric rods made. the aux. pump linkage would need adapting.

4. The wayshaft position could be moved to a location just outboard of the crosshead casting by using a couple of bearing blocks mounted on the back. Alternatively the wayshaft could be mounted on the front (column side) of the engine the bearing blocks incorporating the extra height required for the front columns this would allow "open" rods. Either way the wayshaft needs to be further away from the centreline and higher (see attachment), the longer the reversing arm the less angle required for the quadrant.
Change the link to a longer one with centre suspension (in which case the wayshaft can be either side). Details of centre suspension links see. text books such as Martin Evans manual of model loco contruction.

regards
Jack

Image


steamboatjack
Urchin


Joined: 01 Oct 2007
Posts: 39

Posted: Sun Feb 22, 2009 6:21 am Post subject:
sorry forgot to mention on the sketch just posted, this shows the correct position of the reversing arm in relation to the link, there is no other alternative if you wish to minimise "die slip"
jack


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