The rigid wheelbase of most 4-8-4s falls into the NMRA's "Class N" curve category -- 36-inch minimum radius (30 degree curve) at slow speed. The NMRA recommends going at least one curve class larger for normal operations, for appearance's sake. Therefore, for mainline operating speeds, it is recommended 4-8-4s should have to traverse no sharper than a "Class O" minimum radius curve -- 43 inches (25 degrees), unless one or more of the axles has blind (flangeless) driving wheels. Even the condensed Shinohara version of the number six turnout should accomodate them. I wouldn't want to trust an ATSF 2-10-4 through them, though. Note that these recommedations take appearance into account as well as operation.
Per the railroad's locomotive diagrams, New York Central's Niagaras were designed for a maximum 18-degree curve (slow speed, as in around shop areas). That's 60-inch radius in S Scale. Most commercially made model railroad equipment can easily track through tighter curves than the NMRA's recommended minimums, even if it looks like [supply your own epithet]. Nothing makes me cringe more than full-length passenger cars on a model railroad. For Canadian fans, I was told by a civil engineer friend who is employed in Canadian Pacific's engineering department that CP generally uses #9 turnouts in yards, but will squeeze in a #7 in tight spots. He advises CN has pretty much standardized with #10s but will go down to a #8. I further understand number 8 turnouts were most common in yards in North America in the age of steam, but the #10 became favoured post-WW2 and is now almost universal. The "rule-of-thumb" the railroads use for speeds through turnouts -- maximum speed is double the frog number. That is, maximum speed through a number 8 turnout would be 16 mph. I would think doubling that again would be acceptable for model railroad equipment. Anything faster, though, and it becomes a road-race set. Mainline railroads generally were engineered so that maximum curves did not exceed six degrees (179-inch radius in S), and even this was considered a sharp curve to be avoided if at all possible. Four degrees would be a better maximum. In mountainous areas, maximum curves could bend as much as 12 degrees (90 inches in S) and the Pacific Great Eastern, here in Beautiful British Columbia, bent its steam locomotives around a couple of mainline curves of 16 degrees (67.4-inch radius in S) -- and that with flanges on all drivers! I think those involved in the recent debate over car weights need to consider that model railroad equipment has to operate around curves far, far sharper than they would encounter at road speeds on a railroad. The debate over scale-to-prototype weights becomes one of those apples and oranges arguments unless all other operating factors, including curve radii, are equal. Or ... not. regards ... pqr ----- Original Message ----- From: "Bill Roberts" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, May 04, 2005 8:16 AM Subject: [S-Scale Modeling] Re: shinohara track >> Date: Tue, 03 May 2005 04:40:55 -0000 >> From: "bobcom52" <[EMAIL PROTECTED]> >> >>How does shinohara pointwork geometry compare to nmra s scale standards. >>Anyone able to enlighten me. > > I once measured a Shinohara No. 6 and concluded that the straight > distance of the frog toe was too long. This gives the curved closure > rail a radius sharper than 58 inches, which NMRA RP 12.2 specifies. > > What does this mean? A modeler should be able to run his 4-8-4 > through a No. 6. If he uses the Shinohara No. 6, maybe he cannot. > -- > Bill Roberts, San Francisco CA > > > The poll results are in....... To REPLY to the list, use REPLY ALL, to > reply to the sender, use REPLY. I do NOT know if this works on all e-mail > software, but it works on some of the most common ones. For those of you > on DIGEST mode, all REPLY messages go to the list. > > Change your membership, change your message settings, use our CALENDAR, > view shared files or photos, view the list archives, GO TO > http://groups.yahoo.com/group/S-Scale/ > Yahoo! Groups Links > > > > > > > The poll results are in....... To REPLY to the list, use REPLY ALL, to reply to the sender, use REPLY. I do NOT know if this works on all e-mail software, but it works on some of the most common ones. For those of you on DIGEST mode, all REPLY messages go to the list. Change your membership, change your message settings, use our CALENDAR, view shared files or photos, view the list archives, GO TO http://groups.yahoo.com/group/S-Scale/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/S-Scale/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
