Simplex or Super Simplex

[ron]

Hi All
After a great deal of thought I have decided to build a Simplex and have ordered the drawings from Reeves. [hence the question about CI & gunmetal cylinders]
A friend has since given me a loan of the MEs that detail Super Simplex, and I was wondering if it's worth the extra work, bearing in mind it has a more complicated boiler and I've plenty experience of the 'machine shop' side of engine building but none of boiler making, although I can get help with it.
If anyone has any experience of either I would welcome your comments, and if anyone can point me in the direction of a source for the book I'd be much obliged, they seem to be like hens teeth!
Ron

[jones]

Hey Ron,
I have been wondering this EXACT same thing for quite some time, and I'm just about ready to take the plunge. I am leaning toward the Super Simplex partly because I think it looks better (my opinion, please don't anybody be offended) and because I think the improvements it has should make for a better running locomotive. Not that a normal Simplex isn't a good runner, but... Anyway, I have another question to add. To build a Super Simplex do I also need the plans for the original Simplex, or just the Super plans?

Thanks in advance,
Andrew Barber

[greasemonkey]

HI Ron
Ive got Simplex and if I was to start again I would go the Super Simplex route. Simplex is a competent loco in its own right but in answer to certain of the critisisums Martin produced the super version. Simplex cylinders are a little large in proportion to the boiler/grate size and it benefits from reducing the blast nozel diameter from 1/4" to 7/32" to aid steam production. As designed it doesnt have eithert brakes or cylinder drains not dificult to add but not everyone has the knowldege/abiltiy to be able design from first principals. The additional weight makes it a better preformer when hauling passengers and the larger firebox makes keeping the engine on the 'boil' easier. I thinnk the biggest advantage is the addtional superheat that is available.
Both designs are available from Blackgates and Reeves and I beleive now also MJ Engineering so I would shop around for prices as there is a large difference in cost between them.

Andy

[Nexuas]

Maybe it was beginners luck, maybe it was sheer determination, but I did not find making a boiler that much of a problem...

I built a new boiler for my 3 1/2" gauge RUSSELL in about 8 weeks, I had no previous metal work experience other than watch my dad work on a few bits and pieces, but all the boiler work he has done was mostly before I can remember i.e not in the last 20 years.

Not being familier with the design differences between the two models I can not comment completely, but I would assume the only difference on the boiler is the inclusion of a super heater flue or three, and three larger tubes will be easier to seal than 12 smaller ones...

[ron]

Andrew
It looks to me if you have a bit of model making experience you could build the Super Simplex from the drawings and articles in ME. they ran for 7 issues in 1989, Vol 162 Nos 3846 to 3851 and Vol 163 no 3852.
Andy
Thanks for the info I've e-mailed Blackgates and MJ for prices, presumably Reeves will be the dearest?
Ron

[baggo]

Ron,

In case you are interested there are a few Simplex castings for sale on Ebay including wheels, horns, frame stretchers etc. I've seen a few copies of the book for sale over the last few months so might be worth keeping an eye out for one coming up again.

I managed to snap up a real bargain earlier in the year when I picked up frames, wheels, cylinder castings etc. plus a boiler kit for £250 (for Simplex) so that will be next years project I think. It will be nice to work on something fairly big after my usual 2.5" gauge stuff!

I don't think the boiler for Super Simplex will be any more difficult than that for Simplex as it is not that much bigger, the main difference being three superheater flues instead of just one. I will probably fit an extra flue to the basic Simplex boiler when I get around to building it.

John

[SteveW]

Guy,

A bit off topic but I have a question on a statement made above: why does reducing the size of the cylinders improve the loco?

The focus of my desires is a beast from the Reeves/Piddington stable called 'Locomotion'. Although it's a 7-1/4" gauge it has perhaps the smallest bore of all in the Reeves 24th edition catalogue. Doing the math and adding just an 1/8" to the bore makes a considerable percentage increase in piston area and I assume power to the wheels.

With middle aged spread taking it's toll I have to ensure it'll pull me without struggling. Given a bigger bore (cylinders) just like a CH radiator I can turn it down but not up beyond it's maximum.

[baggo]

Hi Steve,

I presume you are refering to Andy's comment about the Simplex cylinders being a bit large in relation to the boiler size? Obviously the amount of steam the cylinders consume will depend on the bore and stroke - the bigger the bore or longer the stroke, the more steam will be used and the more steam the boiler will have to produce. You have to be careful increasing the bore size without altering the boiler otherwise you will get to the point where the boiler cannot evaporate enough water to maintain pressure. Andy's comment suggests that the steam consumption of the Simplex cylinders is on the limit of the boilers ability to produce steam. Reducing the blast nozzle diameter will increase the draught and increase the temperature of the fire and improve the situation somewhat.

The cylinders for Locomotion do seem very small at 7/8" but that's perhaps to keep to a scale appearance?. I don't know how the boiler is laid out but it may be limited in heating surface. As a matter of interest the three cylinder 2.5" gauge loco I am building at the moment has 7/8" bore cylinders!

John

[greasemonkey]

Hi Steve
John has got it spot on in his reply. If you read Martin Evans book 'The Model Steam Locomotive' he gives two equations for judging steam loco performance in relation to boiler dimensions and cylinder size. The first is grate area divided by number of tubes multiplied by internal diameter and the second is grate area divided by swept volume of cylinders. He sugests that for optimum performance the results should be approx 2.3 and 2.4 respectively. Low figures for the first calculation indicate a boiler that may be shy steamers. High figures for the second calculation imply that the engine would be more efficent with larger cylinders or a smaller grate area and conversley a small figure implys that the grate area needs to be larger or the cylinders smaller.
Looking at the Simplex figures gives a value of 3.05 and 2.08 and these may explain why Super Simplex came into being. They certainly support my findings on the track
All is not bad though as there are a lot of Simplex's out there that do run well but those that do seem to be built by experienced engineers and not beginers.
Has anyone entered the valve grear dimensions into one of the software simulation programes to see if it could be improved?

Andy

[Chris Kelland]

Hi Chaps,

Interesting debate! I have a standard Simplex I use for passenger hauling at the club which it does very well. It is really a question of what do you want to use the loco for? As it stands the Simplex is a super little loco capable of very hard work, but it comes at a price as the boiler is worked very hard so the smokebox soon fills up with char and I have had problems with clinker. over the winter I will make some blast caps to see if I can reduce the draft without losing its ability to make steam.

The Super Simplex would seem the way to go, its looks are a lot less 'freelance' and I think it should perform well. The new boiler should steam very well. though I am not sure it is necessary to increase the diameter of the cylinders as the standard one with 70 or 80 psi on the gauge will pull a dozen people. as far as the new boiler is concerned with its great dose of superheat, I would go for cast iron cylinders and pistons and a reliable oil feed.


Chris.

[chameleonrob]

has anyyone run the simplex diamentions though jim ewins calculations?

pageperso.aol.fr/jemodeng/index_frames.html?f=fs

if the cylinders are a little too big how well does the valve gear cope with knotching back?

rob

[greasemonkey]

Hi Rob
Thanks for that link a useful source of infomation. What happened to Lode Star and his Southern Z class tank, anybody know?

Andy

[greasemonkey]

HI Chris
As you say, it will pull passengers, but you have to work it hard! With the high amount of super heat your right, cast iron is the only way to go for the cylinders. Simplex was originally designed for a working presure of 110 psi!! I dont like the boiler design as standard and built my new boiler with traditional crown stays and not girder stays but 80-90 psi is more than adequate unless you are gong to add a lot of additional weight. The limit with our size engines is the ability to put the power from the cylinders onto the tack and that is limited by its weight. I would certainly put steel tyres onto any engine I biuld now.

Andy

[chris vine]

Hi SteveW,

Do you know what the stroke of the cylinders on Locomotion is? It may be that it is quite a bit longer than the more modern types. Although not usually mentioned in relation to steam engines, it is the cylinder volume which produces the power. A long stroke means a larger crank radius so the cylinder has more leverage on the wheel or crank-axle so to speak......

Chris.

[ron]

John [baggo]I got a set of wheel castings on Ebay for £35 last week, I'll keep an eye out for any other parts being posted and hopefully the book.
As a matter of interest the latest drawings for the standard Simplex now give an alternative superheater of 4X 1/4" SS tubes instead of the original 2X 7/16" tubes for 'builders desiring higher superheat'
Ron

[baggo]

Rob,

thanks also from me for posting that link - the site provides a lot of very useful info. If anyone is interested I've produced an Excel spreadsheet to do all the calculations for the efficiency figures that Jim describes so that you can work out your own for any loco. It can be downloaded at:

www.baggo.copperstream.co.uk/me/misc/locomotiveefficiencyformulaev1.xls

I've put the figures in for Simplex and Super Simplex and there's actually very little difference between the two. The 'Engine factor' is higher but the 'Boiler factor' is lower to compensate. The grate area for Super is actually slightly less than Simplex because although the firebox is 1/8" longer it is also 1/8" narrower.The fact that the 'Boiler Factor' is nearer to the ideal figure is probably due to the extra tubes rather than anything else. Strangely Martin gives the grate area for Super as 17 square inches but I only get it to 15.5 although I haven't taken into account the fact that the grate slopes which will increase the area slightly.

If anyone finds any cock-ups on the spreadsheet please let me know!

Ron - thanks for the info on the Simplex superheater mod - I'll incorporate that on mine.

John

[ron]

John
If you haven't already got them I have a copy of Martin Evans' ME article from April 1987 titled 'Improvements to Simplex' if you want a copy send me your e-mail address. As far as I can see the improvements have been made on the latest set of drawings I got from Reeves.
Ron

[baggo]

Hi Ron,

Thanks for the offer but I have got that issue. I'll dig it out and have a read. I won't be cutting metal till next year as I must finish one or two other projects first! I'll probably draw up a set of full size drawings as I go along as I will probably alter one or two bits to suit myself. My biggest worry is getting enough heat for silver soldering the boiler. It will have to be a two man job I think!

John

[greasemonkey]

Hi John
The boiler can be made single handed as that is how I did mine! Get yourself the large Sievert Cyclone buyrner and you should be okay if you suround the boiler with fire bricks to keep the heat in. I will try and find some time late this evening to enter the valve gear dimensions in Charlie Dockstaders program.

Andy

[baggo]

Thanks for that tip Andy. I,ve heard of the cyclone burners but never seen one. I'll check them out. I've also considered using a lower melting point solder than Silverflo 24 (e.g. Silverflo 40) for the first joints to lower the heat requirements. Silverflo 40 still melts at a higher point than Easyflo No.2 so there shouldn't be a problem with the later joints. It's much nicer stuff to use than 24 as well! I've used it on two 2.5" gauge boilers I've just built.

John