Advantages of Hackworth Valve gear?

What are the advantages and disadvantages of Hackworth valve gear over Walschaerts or Stephenson’s valve gear?

From what I can see on live steam locos Hackworth looks a lot simpler, is this true?

Very much simpler. For an 'improved' Hackworth, look up Marshal gear.

Pete

Being simple is the only advantage. It gives very poor valve events. It was studied in detail and compared to other gears in EIM by Simon Bowditch ?? A few years ago. Also it only fits locos with enough vertical clearance for the rods, eg those with high set boilers.

Very much so, the only problem I think I experienced is that if the axle set that holds the valve operating lever has a lot of movement in it, it does affect valve timing slighly.

For this reason the suspension travel of that axle is kept tighter than the others, but it doesn't really make a difference when you are running.

Valve setting is quite easy as you can see all the moving parts, good for lubrication too.

I did consider on my first loco whether there would be a lot of wear experienced on the linear guide, but that hasn't appeared to be the case.

Regards

Lofty

Yes it's a bit simpler, but as others have said it gives very poor results. The Marshall version is even worse. If you can find ME from 1997 there was a series of articles (by me) which explains it all. It's 15Mb so a bit big to e-mail. If you want simple look at Southern/Bremme, but Walschearts isn't that hard.

Edited By duncan webster on 02/02/2018 22:48:09

Hi Simon,

Hacksworth valve gear does not produce near optimum valve events as the gear is notched up, due to it's simplification. A well designed Stephenson's and Walschaerts valve gear does provide such valve events.

When you also factor in the up and down movement of the driving axle on steam locomotives further compromising the valve events, then it is a poor substitute, except for it's simplicity and cheapness of construction.

I remember as a young Talyllyn Railway volunteer the late Ron Smith (TR Driver) adjusting the valve gear of TR No.4 'Edward Thomas' regularly. If Ron had properly understood the limitations of Hackworth valve gear it is arguable his efforts were in vain.

One of the supreme rare enjoyments of miniature locomotive driving is to have a loco with superheaters and a decent valve gear when you can open up the regulator and wind back the reverser to 20% cut off and drive on the reverser as per fullsize steam express locos! You adjust the reverser from between 25 and 15% cut off to cater for all track conditions and a heavy load of punters behind.

Very few miniature locos can be driven in this way.

Cheers,

Julian

Some years ago, visiting the Worthing Club, a member exhibited a much modified Sweet Pea (As I recall. Think that it was now a 2-6-2, and was called a Wasp; "was a Sweet Pea" .

One of the modifications was to fit Southern valvegear. The owner explained that it dispensed with the problem of wear in the die block and slide, and turning new bushes and shafts would be an easier job.

Have no idea what sort of valve events the Souithern gear produces, but it seemed a neater solution.

Howard

Edited in hope of removing an emoji!

Edited By Howard Lewis on 03/02/2018 02:54:30

Orenstein & Koppel mention in their 1913 catalouge that this kind of valve gear is much less prone to damage from trees,stones,scrap etc in rough working places.

**LINK**

How important are good valve events when notching up on small industrial narrow gauge locomotives that typically worked slowly and over short distances? I suspect that the answer will be as different for the prototype locomotives and for miniatures as the conditions in which they are operated, and that the manufacturers of industrial locomotives knew what their customers needed when they offered Hackworth valve gear.

Brian

Hackworth seems to work well enough on all the Sweet Peas that I have seen running. It has its faults, but so do most valve gears, Hackworth is simple to make and repair, no eccentrics or expansion links to machine.

I've also thought Southern valve gear to be an elegant solution dispensing with any sliding motion as part of normal valve gear operation. It seems to be relatively ignored in most discussion on valve gears, and I too would be interested in any comparison with the more popular valve gears in relation to valve events and loco performance.

Geoff P.

for details of Southern gear see ME for 20 June 1997 and 6 Aug 2004. In principle it is very similar to Hackworth/Marshal, laid on its side with a bell crank. The reason it gives better results is that the vibrating lever is a lot longer, and so the angularity error is a lot smaller. If anyone is really interested I might have a copy of Bill Hall's simulation program (no guarantees, my filing system is chaotic), no doubt Charlie Dockstader covered it, but you might have to consult DosBox to make either of them work.

​Brian Remnant had Bremme gear on his Sweet Pea and won Imlec with it so it can't be all bad. Bremme and Southern are very similar.

Only speaking from experience with my 'Pea', I normally find that as soon as I get moving 2-3 mph I can notch all the way back and it will pull quite happily with me and two passenger trolleys coupled up.

regards

Lofty

Thanks Duncan, i don't have those ME's but do have the Dockstader simulation, but i was hoping someone with experience of Southern valve gear in use might have some comment to share.

I'll also look up the Bremme gear.

Cheers, Geoff P.

Had a look at the Dockstader simulation for the Bremme and Southern gears, the similarity in principle with these gears is easy to see, but the horizontal orientation of the Southern gear with the long eccentric rod means that it is much less affected by vertical movement of the driving axle.

Regards, Geoff P.

The Bremme gear on Dockstader's website is not the one I was referring to, perhaps Mr Bremme had several gears to his name. The version I meant was pretty much as Southern, except that the curved slot member is replaced by another radius bar pivoted where the centre of curvature of the slot would be. See ME 5 jan 73. I suspect Southern is somewhat sturdier, there is a lot of potential for generating side slap in this version of Bremme. The file is 8Mb, so can be e-mailed to anyone interested. Bill Hall's articles on Southern are also <10Mb so could be e-mailed.
The reaction to vertical movement is not as simple ​as it looks. With Hackworth the effect on valve travel is reduced by the tangent of the angle of the slide, with Southern/Bremme it is reduced by the lever ratio of the horizontal beam. In both cases of course it is worse than Walschearts or Stephensons

Good afternoon,

I think most have concured the gear is fairly simple and in the context of full sized locomotives (mostly narrow gauge industrial types) it was simple and cheap to produce, most locomotives of that type were employed on very short trips where economics in respect of coal consumption were not really considered, now, if it was any good the main line operators would have used it. I don't think Riddles would have considered it suitable for say the likes of the Britannias or the 9Fs, no, it may be suitable for the likes of a narrow gauge shunting type shuffling up and down a few yards as and when demand required.

Regards,

Bob

Thanks Duncan, that makes sense. I'll look online for more info on other gears attributed to Bremme. No need to email those files, my email system would probably struggle with files of 8-10MB.

Regards, Geoff P.

Well that seems to have panned Hackworth valve gear comprehensively. A friend's Romulus has not heard how bad it is. Which is fortunate, as it works extremely well in practice.

Andrew.

Edited By Andrew Tinsley on 05/02/2018 16:01:38

Hear Hear