Tich 7 1/4 gauge

[HaydenI.]

Im going to build a 7 1/4 gauge Tich from drawings of a 3 1/2 gauge from L.B.S.C. Now I know it's going to be hard, but I know a few engineers and I have come up with the equation for 3 1/2 to 7 1/4 and it's something like 2.07149 times the original number. so Im going to start like anyone else with the frames.

 

[stevehuckss396]

Super project.

If it were me, I would re-draw the entire thing in the new scale before cutting anything. Convert all the holes for fasteners and bearings if there are any. Could save some time in remaking parts later.

How ever you go about it, best of luck and i'll be watching.

 

[kvom]

From my experience with the Kozo A3 scaled from .75 to 1.5, the "gotcha" is that the frame width and everything lateral to the frame does not scale. It's best to start with the IBLS wheel spacing dimension and compute all lateral dimensions from that. The longitudinal and vertical dimensions should scale properly.

As Steve says, fasteners and holes can be adjusted fairly freely. Similarly, rod diameters. If you use O-rings for seals, then the sealed shafts would need to be sized to the rings.

 

[dalem9]

Hi Rudy Kouhoupt has a tape that tells you how to scale up or down .I have it and it is realy good.Covers alot of the main topics that you will need to know. I beleive it's by village press. Hope this helps .Dale

 

[HaydenI.]

Thanks to all and I will go have a look for the video. Steve, I have talked to the members at my club MVR (Morphett Vale Railway South Australia) and they said that if I work to .1 of a mm i should get it all correct and the wheel spacing, I have worked it all out and the frame and beams will be good for the gauge and the wheels should then fit but I'll take the wheels down to the club and test the gauge and as long as I follow AALS standards it will work.
All ideas are welcome as well.
Thanks to all.

p.s I have had this project going since April this year and I have most of the frame done.

 

[stevehuckss396]

p.s I have had this project going since April this year and I have most of the frame done.

Pictures as you go!!

 

[Maryak]

Hayden,

Welcome to our forum. wEc1

If I am correct that makes 6 of us in greater Adelaide. The Xmas party may need 2 bottles of steam now :

Best Regards
Bob

 

[HaydenI.]

These are not the greatest but they work I cut these when I first had almost nothing and no access to a mill and no milling attachments for the lathe. So these were cut by hand.
And the spacer was meant to be cast but a lot of people just weld a few pieces together like I did.

 

[HaydenI.]

The Plate will become my braking system and the angle and thicker plate will become the reverser and the other 2 are my frame so far ready to be bolted.

 

[GWRdriver]

Hayden,
Are you aware there is a full set of drawings for a Double (7.25"ga) Tich available? These were originally from Chas Kennions, now owned and offered by GLR Distributors in the UK. But no matter, the word on the 2X Tich was that it was with very few obvious detail exceptions a simple doubling of the 3.5"ga version, even the valve gear although I'm sure the 2X Tich geometry would benefit from a fresh look.

My 2X Tich is perhaps 60% done, using the Kennions drawings as a starting point and redesigning almost everything to accommodate 5" drivers (from the Ken Swan Bridget design), larger cylinders, a Belpaire boiler, and a few other "improvements." Unfortunately my photos aren't on this computer but I'll try to post a few in the next couple of days.

 

[HaydenI.]

GWRdriver,
i didnt know about them drawings but no matter ill keep going with what i started and this loco dosnt have to pull anything because our track is the hardest in SA i think and beaing such a small loco it might pull 1 or 2 cars and that would be all but why are you putting larger cylinders on and a Belpaire boiler on?? not to be rude i just wonder does it really need it?
thanks for the tip as well
cheers
hayden

 

[HaydenI.]

and here are some more photos of the loco with the hornblocks in and a milling op (i keep forgetting to take photos while machine...) and the frame complete (just have to mill the inside out)

 

[kvom]

Larger boiler for larger cylinders for more power I presume.

 

[GWRdriver]

GWRdriver, i didnt know about them drawings but no matter . . .

Right. No matter, I also would have ended up redrawing, and have redrawn, the entire engine so it didn't matter at all whether I started with drawing for the 3.5"ga version or the 2X version. Forge ahead!

As for the cylinders, I elected to make a pattern and have them cast so on that account I could do whatever I wanted to do. But I spent some time corresponding with folks in the UK (and one in the US) who had either built, or run, or owned the 2X, about what if anything they would do to improve operation, performance, etc, and in every single case the recommendation was to increase the cylinder bores by at least 1/8". There was even a recommendation to go to alternative cylinder castings (from the 5"ga Simplex IIRC) but that change didn't look right on paper, and wouldn't match my throw, thus the new castings. This change not only increased power but resulted in a better performer in general and made it a pleasure to drive. The stock boiler design was apparently sufficient to absorb this change without any difficulty.

Another strong recommendation was to "lock" the rear axle, that is, to make it rigid and unsprung so as to create a three-point suspension. This apparently results in a more stable ride, less pitching on uneven track, more adhesive weight on the drivers, and in general better handling for an 0-4-0. I had already sprung my rear axle in the usual way but it can easily be locked so that I can eventually try it both ways.

Kvom, as for the Belpaire boiler, . . . there's really no other reason other than I just like them. I've built several and find them easier to build and stay at the firebox end than round tops, and the TICH looks good with one, so it's simply a personal preference.
Cheers,
Harry

 

[HaydenI.]

Thanks GWRdriver
me, personally i don't like to change plans just because if its built that way its an original form (but ill will be adding a couple of injectors and compressor for running purposes on a big track and for AALS standards) unless it is going to be a OH&S risk. which i don't think it will be just because of it age!
The locking of the rear axle would that eventually fracture the axle if the track was not to a almost perfect stranded (which a track can never be!) just because of the vibrations?
and to all this is where the project starts to slow down because schools back in 3 days so i wont be in the workshop all the time to build.
thanks
Hayden

 

[GWRdriver]

The locking of the rear axle would that eventually fracture the axle if the track was not to a almost perfect . . . just because of the vibrations? - Hayden

Hayden,
In a word, no. If made too small in diameter one might somehow bend an axle by excessive loading, or by an accident such as being dropped, but otherwise normal or even abnormal operations wouldn't cause an axle to break or crack. (We should also be using steel for axles which is tough rather than brittle.) The rigid axle will cause the loco to move with the irregularities in the track, thus producing some side to side rolling, and the loose axle will accommodate this. But there is going to be engine movement (roll, pitch, yaw) with any track irregularity and the objective is to minimize this, which the 3-point suspension will do.