jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 17, 2016 0:24:11 GMT
i cannot be certain, as ive never seen or driven a 5"g Dougal, but i should imagine most builders will have made some significant departures from the published drawings. Dan has kindly sent me copies of the drawings in the last few days. i havent seen the drawings for many years but nothing has changed my original view of the design in the last few days.
the drawings are rather lacking in details in many respects and especially with the boiler. as a 'simple' beginner's loco the drawings are very poor. a beginner needs far more detail.
as drawn, i would have considerable reservations about the original boiler, plus its proportions due to the heavily simplified inner firebox and outer firebox wrapper and a few other features.
cheers, julian
|
|
|
Post by mutley on Feb 17, 2016 20:56:29 GMT
My sons one runs well. You need to be on the ball with it as the firebox and boiler is small but no complaints.
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 17, 2016 21:29:08 GMT
i suppose it depends by what you judge 'runs well'?!
i dont want a loco that develops hydraulic lock because it has tortuous steam passages, an isolated steam chest of the most peculiar pattern, and no superheat, and no drain cocks on the cylinders.
i dont want a small 5"g loco with 3/16" wide steam ports that make a complete nonsense even of the slip eccentric valve gear.
i dont want a loco with such a shallow firebox that the odd misplaced shovelfull of coal will block the lower tubes.
i dont want a boiler that isnt free steaming so that it has to have such a sharp exhaust that clinker is formed.
i dont want a loco where the smokebox draughting allows the exhaust to impinge upon the regulator/wet header block in the smokebox.
i dont want to have an unstayed inner firebox that due to it's proportionate length is liable to crushing on the crown.
i dont want a boiler with no blowdown valves.
i dont want a screwdown regulator that is prone to seizing up when not in use.
if i were a beginner i wouldnt want to build a loco without proper detailed drawings. 3 sheets only of sparse drawings littered with errors and in the case of the boiler without proper detail that i consider quite dangerous! (eg where is it shown on the drawings that the throatplate is to be flanged?)
cheers, julian
|
|
|
Post by mutley on Feb 17, 2016 21:39:01 GMT
LOL..... if I took anything you say seriously Julian I wouldn't go near my workshop however I was asked how MY engine ran. No one asked if it was per drawings or had been modified at all. Look at the pictures Julian and then engage your brain.
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 17, 2016 21:58:08 GMT
i like Dougal in fullsize!
but the 5"g version as per the drawings i dont like!
the problem arises when a beginner tries to build the loco to the drawings. ive built a couple of locos with no drawings whatsoever apart from the boiler and valvegear i worked out on paper and made proper drawings of. my 3.5"g GWR King is built to the Jackson/Clarkson drawings which arent much better than the Dougal drawings! but the Jackson/Clarkson GWR King isnt a beginners loco.
i think that Dougal in 5"g needs a complete redesign. to bring the boiler up to current spec and improve it, and with superheaters. to have prototypical valve chests vertical up against the cylinders. to have a decent valve gear instead of slip eccentrics.
i am sure many builders have done many or all of these things themselves, including Mutley/his son.
but Dan is building the loco to the drawings!
cheers, julian
|
|
|
Post by mutley on Feb 17, 2016 22:02:04 GMT
Ahhh yes of course that's right your the exspurt aren't you.. must remember that.
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 17, 2016 22:07:39 GMT
Mutley,
ignore what ive built or done please!
my only concern is that Dan doesnt get thoroughly fed up with the design as drawn and spends a great deal of valuable spare time plus money on a poor design and as a result gets fed up with the hobby!
cheers, julian
|
|
|
Post by mutley on Feb 17, 2016 22:37:09 GMT
Julian, after your display tonight I think most people will ignore what you've done. I've never assumed to know everything, I've always sort a range of opinions and then taken a balanced view. If you want to be critical then go ahead but a beginner wants to be encouraged not told the model he's chosen is rubbish. By your own admission you've never driven or seen a 5" Dougal yet tonight you've declared it to to be a poor design on the basis of the drawings alone. Very few of the model designs are perfect but successive generations have found a way around the problems and that's the beauty of being a club member.
|
|
chrisb
Part of the e-furniture
Posts: 345
|
Post by chrisb on Feb 17, 2016 22:49:03 GMT
Julian
l take note of a lot of your comments. With mine being modified for 7 1/4" I have come across some of the things you mentioned.
I added bosses for drain cocks to my cyl patterns, allowed a bit more 'meat' in the cyls and steam chest for larger steam passages.
I am looking at the boiler desgn with respect to the round topped, unstayed inner firebox, also looking at using a sparate firebox outer wrapper, rather than unwrapping a portion of the barrel tube to allow a deeper firebox. Probably going for a ball valve regulator with a removable dome. I have made smoke box separate rather than an extension of the barrel.
I have left the slip eccentrics as it was supposed to be a simple 'quick and dirty' build, although I have been distracted by 2 3 cyl Triumph bikes
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 17, 2016 22:51:53 GMT
Mutley,
that is a bit off!
we do try and help people here!
a Speedy builder gets referred to Don Ashton's valve gear re-design.
a Lion/Titfield Thunderbolt gets referred to Saxby's modifications etc.
Simplex builders are cautioned about the original boiler design.
Pansy builders are cautioned about valvegear problems and much else besides.
we try and help wherever possible, to avoid the scrap bin for others in making parts.
we try and help with methods of making parts.
some of us help in re-designing parts of a loco or making new bits for fellow forum members and friends to get bits to work.
we do try and help!
cheers, julian
|
|
|
Post by mutley on Feb 17, 2016 22:59:26 GMT
If tonight was your idea of help then I'll stick to my club thanks.
|
|
|
Post by ejparrott on Feb 17, 2016 23:24:12 GMT
As it happens, I agree with Julian's points.
|
|
dc309
Seasoned Member
Posts: 146
|
Post by dc309 on Feb 18, 2016 0:05:57 GMT
Oh dear, I seem to have started WW3!!
Many thanks for your input Cro and Mutley - much appreciated! Thanks also Julian - I take your comments on board about the faults on the loco, so I'll have a word with my club inspector on the boiler to see what he thinks and what he would change... I'm a long way off the boiler yet though! With regard to working to the drawings I think if I can make it work that is an achievement in my book, so I shall see where it can be improved. I would quite like to fit Stephenson valve gear so it is closer to the original loco, if it isn't too difficult.
Thank you all for your input again!
Dan
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 18, 2016 0:18:09 GMT
hi dan,
i will email you a few suggestions re the boiler in the next few days, with perhaps a few drawings. they might also be of interest to chrisb.
i think the firebox throatplate needs setting back a bit to give clearance for a proper loco link stephensons valve gear. this isnt a problem.
if the port width is reduced by half to 3/32" we can probably fit in a decent valve gear. this is the same port width as LBSC's Maisee and there are plenty of excellent runners of this type with the same 1 1/4" dia cylinders, though i would advocate a bore of 1 1/8" for Dougal if the castings allow.
cheers, julian
|
|
dc309
Seasoned Member
Posts: 146
|
Post by dc309 on Feb 18, 2016 0:30:52 GMT
Hi Julian,
Thanks for that!
Will it make much difference to the power of the loco reducing the cylinder diameter by 1/8"?
Dan
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Feb 18, 2016 0:38:24 GMT
hi dan,
if we re-design the boiler to have superheaters, and have a decent valve gear, and avoid a few other problems, then i am quite sure 1 1/8" bore cylinders will produce enough power verses adhesive weight of the loco.
there is no point having cylinders that are too big for the adhesive weight of the loco.
cheers, julian
|
|
|
Post by ejparrott on Feb 18, 2016 9:44:10 GMT
Dougal is not a public running passenger hauler, 1-1/8" cylinders will be fine. If in doubt, raise the boiler pressure, but you won't need to.
|
|
dc309
Seasoned Member
Posts: 146
|
Post by dc309 on Feb 18, 2016 10:24:32 GMT
Dougal is not a public running passenger hauler, 1-1/8" cylinders will be fine. If in doubt, raise the boiler pressure, but you won't need to. Is it too small for public hauling? Surely it'd be as good as some of the 3 1/2" gauge engines? Cheers, Dan
|
|
|
Post by Cro on Feb 18, 2016 10:28:39 GMT
My friends Dougal is built with no superheaters, 1 1/4" bore, drawn boiler (as far as I know) and it runs very well and has done the odd passenger hauling afternoon. Ok it only takes one trolley of passengers but it will do it! Also upping the pressure??? really?! thought as a boiler inpector that's not something you just suggest without a bit of calculation and re-design? ?
|
|
|
Post by ejparrott on Feb 18, 2016 12:27:33 GMT
I was taking the redesign of the boiler by Julian as a given. Upping the boiler isn't something to be done on a whim.
|
|