| Author |
 Topic  |
|
Foreman
1st Class Member
USA
|
 Posted - 04 Nov 2006 : 13:27:16
|
I saw this idea at the recent Sonny Wiselman & Bill Turkel steam ups. Larry Bangham had fitted his new Accucraft 0-6-0 Switcher with a petticoat pipe and exhaust nozzle to get a more pronounced chuff. Now I’m new to this steam game, but it was the best sounding chuff I’ve heard out of a model to-date.
Being a tinkerer at heart, I thought about doing a poor-mans version of what Larry had done, but for my Ruby and no machining….only hand tools, a hacksaw, drill press & files.
As I understand it, the nozzle’s diameter should be about 10% of the diameter of the cylinder’s diameter in order to not create undue exhaust back pressure. So for the Stock Ruby cylinder of 3/8” diameter, 10% is just over 1/32” diameter nozzle. I did some additional research and the larger engine designers use about 16%, but they are also trying to create a draft on the fire by creating a vacuum in the smokebox. That’s not the goal here…I only want a better chuff without creating additional exhaust pressure.
Since I want to stick to off-the-shelf items to make the nozzle and petticoat pipe (a no machining capability needed approach). I chose a 1/16” outside diameter copper tubing, which luckily has an inside diameter of 1/32” + and it telescopes tightly into the stock Ruby exhaust pipe. After acquiring a replacement exhaust pipe from Accucraft, I cut exhaust pipe to about ¾” long, including the threaded portion. I then cut a ¼” long piece of the 1/16” diameter copper tube and inserted it into the cutoff exhaust pipe, then crimped it to hold the nozzle in place.
Now onto the petticoat pipe…I visited the local hardware store and found ½” copper pipe end caps. The inside diameter of the cap is actually 5/8”, go figure, oh yeah, I remember, copper pipe is measured by its inside diameter. The 5/8” is more than enough for the stock smokestack nut to fit up into. I then drilled a 29/64" hole into the closed end of the end cap allowing clearance (with some filing) for the smokestack nut’s threads. I then inserted the smokestack into the top of the smokebox, added stock Ruby smokestack contoured spacer up inside the smokebox, followed by the petticoat pipe, and all held in place by the smokestack nut screwed up into the smokestack. Sorry about being so longwinded here.
Here are the newly purchased supplies:
Shows the hole drilled in the end cap & smokestack nut:
Shows the assembly pieces in the order of assembly:
Smokestack nut inserted:
Assembled, ready for a first firing:
I left the end caps length alone for now, it’s 5/8”….I may shorten the petticoat’s skirt after I fire up the loco, to see if that affects the chuff sound.
More later!!
|
Edited by - on 05 Nov 2006 11:29:09
|
|
|
Engineer
1st Class Member
United Kingdom
|
Posted - 04 Nov 2006 : 15:43:17
|
Ahah! A petticoat...
Good idea and a good post with excellent piccies.
Stephenson did it first though, in 1829.
tac
Ottawa Valley GRS |
 |
|
|
Engineer
1st Class Member
USA
|
Posted - 04 Nov 2006 : 23:53:20
|
| Why do they call it a pettycoat pipe or skirt? |
|
|
|
Engineer
1st Class Member
United Kingdom
|
Posted - 05 Nov 2006 : 03:24:57
|
quote:
Originally posted by Chris Scott
Why do they call it a pettycoat pipe or skirt?
Chris - I believe it is because the shape of the small canopy attached to the blast pipe is not too dissimilar to the outline of a Victorian lady's petticoat - hence the name.
tac
Ottawa Valley GRS |
|
|
|
Foreman
1st Class Member
USA
|
Posted - 05 Nov 2006 : 08:38:47
|
quote:
Originally posted by Chris Scott
Why do they call it a pettycoat pipe or skirt?
I believe tac has it right....here's a picture showing the flaired skirt shape:
I wonder if this is where the saying "blowing smoke up your skirt" came from
|
|
|
|
Engineer
1st Class Member
USA
|
Posted - 05 Nov 2006 : 16:08:01
|
quote:
Originally posted by maculsay
quote:
Originally posted by Chris Scott
Why do they call it a pettycoat pipe or skirt?
I believe tac has it right....here's a picture showing the flaired skirt shape:
I wonder if this is where the saying "blowing smoke up your skirt" came from
Tac
Thanks, I thought it might be something like that, but you ever really know in the world of steam 
|
|
|
|
Engineer
1st Class Member
USA
|
Posted - 05 Nov 2006 : 16:18:14
|
| How does one reconcile the increase in power or improved running achieved by enlarging the exhaust pipe, indicating the existing exhaust pipe was too small (a fairly common one of those Accucraft locomotive improvement items), with the reducing the exhaust pipe's diamter for improved sound quality? This reduction would seem to me to only further limit power or degrade te loco's running. |
Edited by - on 05 Nov 2006 16:19:58 |
|
|
|
Foreman
USA
|
Posted - 05 Nov 2006 : 18:51:15
|
| Venturi effect? My best guess. |
|
|
|
Foreman
1st Class Member
USA
|
Posted - 05 Nov 2006 : 19:30:12
|
quote:
Originally posted by Chris Scott
How does one reconcile the increase in power or improved running achieved by enlarging the exhaust pipe, indicating the existing exhaust pipe was too small (a fairly common one of those Accucraft locomotive improvement items), with the reducing the exhaust pipe's diamter for improved sound quality? This reduction would seem to me to only further limit power or degrade the loco's running.
Chris....my testing should give me some indication and I can always remove the nozzle portion and return to the original sized exhaust pipe. Right now, I'm trusting Larry Bangham's 10% rule that I stated in an earlier message.
I don't think I'll get much of a venturi effect unless I add some shape to the petticoat skirt and follow standard height vs. diameter formulas.
Time and testing will tell, I hope.
|
|
|
|
Engineer
1st Class Member
|
Posted - 07 Nov 2006 : 20:29:30
|
| Howard, the best chuff enhancer I've ever heard was the one Winn Erdman came up with for his C-16 (it's in this forum, somewhere). He silver soldered a "funnel" made of telescoping tubing sections from the top of the exhaust tube (he cut it off, but I didn't see how short) into the stack. It's basically a megaphone, and it sure works. |
|
|
|
Conductor
1st Class Member
USA
|
Posted - 08 Nov 2006 : 08:22:13
|
| That's typical, one guy's mod works for him but not for me...I tried the funnel/megaphone trick with my Mimi(Ruby) , and it totally ate up the chuffs. I had a stealth Mimi, guess I should paint it flat black :-) |
|
|
|
Engineer
1st Class Member
USA
|
Posted - 08 Nov 2006 : 23:26:09
|
quote:
Originally posted by FH&PB
Howard, the best chuff enhancer I've ever heard was the one Winn Erdman came up with for his C-16 (it's in this forum, somewhere). He silver soldered a "funnel" made of telescoping tubing sections from the top of the exhaust tube (he cut it off, but I didn't see how short) into the stack. It's basically a megaphone, and it sure works.
The two threads on Winn Edmns's work:
C16 lack of power, spitting; Fixes
http://www.mylargescale.com/forum/topic.asp?TOPIC_ID=40536
C16 lack of power, spitting
http://www.mylargescale.com/forum/topic.asp?TOPIC_ID=39203
|
Edited by - on 09 Nov 2006 10:56:03 |
|
|
|
Foreman
1st Class Member
USA
|
Posted - 09 Nov 2006 : 10:53:04
|
quote:
Originally posted by maculsay
quote:
Originally posted by Chris Scott
How does one reconcile the increase in power or improved running achieved by enlarging the exhaust pipe, indicating the existing exhaust pipe was too small (a fairly common one of those Accucraft locomotive improvement items), with the reducing the exhaust pipe's diamter for improved sound quality? This reduction would seem to me to only further limit power or degrade the loco's running.
Chris....my testing should give me some indication and I can always remove the nozzle portion and return to the original sized exhaust pipe. Right now, I'm trusting Larry Bangham's 10% rule that I stated in an earlier message.
I don't think I'll get much of a venturi effect unless I add some shape to the petticoat skirt and follow standard height vs. diameter formulas.
Time and testing will tell, I hope.
I got some testing on blocks completed and I find no apparent reduction power to the drivers....nothing scientific, just finger pressure on the wheels. The difference, so far, is visual...the steam really shoots up the smokestack with gusto. Looks neat! I'm thinking if I am going to get an improved chuff, it'll come when pulling a load, hopefully.
I'll try pulling a load at the next Steamup this Saturday. I've got to get some track laid |
|
|
|
Foreman
1st Class Member
USA
|
Posted - 09 Nov 2006 : 10:58:16
|
quote:
Originally posted by FH&PB
Howard, the best chuff enhancer I've ever heard was the one Winn Erdman came up with for his C-16 (it's in this forum, somewhere). He silver soldered a "funnel" made of telescoping tubing sections from the top of the exhaust tube (he cut it off, but I didn't see how short) into the stack. It's basically a megaphone, and it sure works.
Yep, I saw his message threads. Thanks. Lots of clever folks on MLS. |
|
|
|
Foreman
1st Class Member
USA
|
Posted - 13 Nov 2006 : 21:18:01
|
At this last Saturday's steamup, I got a chance to closely examine both Larry Bangham's and Kevin O'Connor's Accucraft 0-6-0 S-12 switcher and decided I would redo my petticoat pipe to reduce its diameter. I also had to remove the smokestack at one point to make a burner adjustment and it was a very tedious task to get the smokestack nut unscrewed because it sits up in the petticoat pipe. To kill 2 birds with one stone I took a short piece brass tubing and silver soldered it up into the nut's opening, instead of the nut up inside the petticoat pipe. Now I have something to grab onto to unscrew the nut.
I also saw what Kevin & Larry had done to prevent the stream of water (condensation from the cylinders at start up) that was shooting up 10 feet or so on my Ruby. I made a four legged spider out of .015" brass sheet that fits into the smokestack and still gives plenty of space for the exhaust to get by.
|
|
|
|
Foreman
1st Class Member
USA
|
Posted - 26 Dec 2006 : 00:38:01
|
Here's the latest incarnation of a petticoat pipe for my Ruby's stock smokestack. I found a 1/4" copper adapter fitting (female pipe threads on one end and 1/4" male slip-fit on the other) that I used with a little modification on my drill press.
I first shortened the female thread end by removing all but the part that flairs out. Then I decided to remove the threads from inside the fitting by using a succeedingly larger sizes of metal drills to get the inside of the fitting to be flared like the outside.
These are all of the sub-assembly pieces of the smokestack. Note that the stock knurled nut has a brass sleeve silver soldered inside, something for the petticoat pipe to slip over and silvered soldered:
And finally, a fuzzy photo (sorry) of the petticoat pipe assembled with the Ruby smokebox.
The inside shape of the petticoat pipe along with the increasing taper of the top smokestack piece is starting to represent a venturi, which should speed up the exhaust steam's velocity. Probably not enough to measure, but it looks better
|
|
|
|
Topic |
|
All Forums
A Petticoat Pipe & Exhaust Nozzle
Forum Locked
Printer Friendly