Peveril valve gear

[chester]

Can anybody explain how the valve gear works for the Peveril the wayshaft goes through the valve gear but move the reversing lever the shaft rotates but has no way of moving the valve gear.Thanks Chester

[mbrown]

I assume it is Allan Straight Link valve gear as on the real IoM locos.

Allan gear has two arms on the weighshaft - one pointing forwards and one rearwards. One (usually the front one) carries a lifting link which lifts the rod connecting the die block to the valve. The other (rear) lifts the expansion link. The eccentric rods constrain the expansion link to move on one radius as it goes up and down, and the valve rod moves the die block in a similar radius facing the other way. Properly designed, these radii cancel each other out so that the movement of the die block from forward to reverse is in a straight line - hence the link can be straight and not curved as in Stephenson gear.

Not sure if that is helpful as your question doesn't include much detail about the problem, but if you can be more specific I ma sure plenty of members here will shed light on it.

Malcolm

[jma1009]

I agree with Malcolm, except his carefully worded caveat to encompass 'Dolgoch'!

I have the Peveril drawings, and to be honest, Graham, I don't know what you are failing to understand about Allan valve gear - the valve rod goes up as the straight link expansion link goes down when you move the reverser, and vice versa in the other direction of the reverser.

It got around the Stephenson valve gear patent till it ran out, and also allowed a lower centre of gravity with a lower slung boiler - the latter point quite important for narrow gauge locos with inside valve gear.

Cheers,

Julian

[jma1009]

(As an aside, the arms of the weighshaft are not equal, and I have read some stuff about Ffestiniog Railway 'Prince' being rebuilt in 1955/6 with the weighshaft off 'Little Giant' and that it was initially fitted the wrong way round!

How this got past the eagle eye of Morris Jones is quite beyond me!

Don Ashton and I discussed Allan valve gear many times - at my prompting - as it is a valve gear that I have always been interested in).

[chester]

Hi thanks for the replies if you move the reversing lever it moves the reach rod that turns the weighshaft and that is all the the shaft turns inside the valve gear but nothing else moves.

[suctionhose]

Key, pin, grub screw missing or sheared?

[mbrown]

It certainly sounds as if the lifting arms are not properly fixed to the weighshaft. If this is an unfinished, part-built, model it is possible the builder didn't get around to pinning the weighshaft together. If it has been in use maybe, as "suctionhose" suggests, the pins have broken.

Often, the front-facing and rear-facing arms on the weighshaft in Allan gear are made in one piece and, if I remember Peveril correctly, they are made from quite solid blocks of steel (one for each set of valve gear). The weighshaft itself would pass through these, but they should be solid with the shaft and it should not rotate within them.

Are there holes for a pin through these arms to secure them to the shaft itself? If not, you may need to drill from scratch - and that needs the levers on the weighshaft to be very carefully aligned so that the left and right hand sets of levers are aligned and correctly oriented to the lever on the weighshaft which connects to the reverser.

This is much easier to explain with a drawing, but if you compare my note here with the drawing of the Peveril valve gear (do you have the drawings) or to the actual arrangement on the model in front of you, I hope it will be fairly obvious what I am getting at.

Good luck.

Malcolm

[chester]

The drawing and the so called build notes do not mention drilling or grub screws in the valve gear it is to drawing dimensions. I bought it part built i have done a lot of work on it that having first seen it you would have thought a lot of the parts would have been there that wasn't build notes are in Dons llas in two issues and covers about eight pages and the valve gear about half a paragraph just saying it is Alan valve gear and built like launch gear.There is very little on the web and what there is is not very complementary on that type of gear.I shall need more than good luck Malcolm more likely a fourteen pound sledge hammer.Thanks for your suggestions i will drill and tap a couple of 3mm tapped holes and see what happens.

[Deleted]

Hi Graham...I found this page that gives some details on the Allan valve gear...not sure if it answers your question or not but might have some useful information...scroll down the page a little to find the relative section.

www.railwaywondersoftheworld.com/valves1.html

Kind Regards

Pete

[mbrown]

You might find that a touch of Loctite would usefully supplement the grub screws. Or, if you have a taper pin reamer, a taper pin would be a good way of fixing them.

Malcolm

[Jim Woods]

Hello,

Don't use grub screws. as Malcolm says, taper pins are best. I have done this with both the IOM loco's I have built. I have send you a PM regarding this valve gear

regards

Jim

[stevep]

Following on from Jim's suggestion - I think I would re-word it to say "don't rely on grub screws to hold the arms".

I would fit the arms with grub screws so that you can adjust them to the correct position and then hold them there. Then you can drill and ream for the taper pin to make absolutely sure they won't move in the future.

[steamer5]

Hi Jim,
Sent you a PM

Cheers Kerrin

[chester]

Thanks Pete i have seen it before on a another web page.
Malcolm and Steve the grub screws are a temporary to try to get it running and then a more permanent fixing.
Good Morning Jim well it is here i will be in touch a bit later.
Thanks to you all for your input i will have another try later.