July 21st, 2011, 01:30 PM #1
44-tonner and Others Minimum Radius...
I'm working up a plan for an urban switching layout (car float to industry with tracks on the street and in alley sorta thing) and wanted to know the minimum practical turning radius of the 44-tonner from Bachmann, as well as the Atlas GP-7/9. If possible, I'd like to use 4" radius curves to allow for tight city street kinds of clearance. And if these can't handle it, does anyone have suggestions for modifications to enable such a thing? Otherwise, how about suggestions for other locomotives that have the ability to take sharp curves. Would need to be American locomotives that might be used from the 1950s through 1980s time periods.
OK, your mission, if you choose to accept it, is to answer these questions for me. This board post will self-destruct in 5 minutes...
July 21st, 2011, 02:16 PM #2
Wow, and I thought my 8" curves were tight....
I haven't tested the 44-tonner on anything that tight (4"), but I will tell you that I've had to make at least some modifications to virtually all the freight cars I own to get even the 40' cars around 8" radius, and pretty much forget the 50' cars. The 44-tonner doesn't even whimper on 8" curves.
The GP7/9 is really beginning to struggle at around 9", and the coupler overhang is so bad that you'll derail anything coupled to it even with 1016 shanks on it. You'll need to be looking for legacy stuff with truck-mounted couplers.
I don't think your biggest problem will be the 44-tonner, its pretty nimble, but finding cars that won't hang up the couplers, trucks, or both on anything that sharp will be a challenge. All have to be truck mounts, but many still can't swing that tight without banging flanges into bolsters or frame parts.
The nicest tight turnouts are the Peco "SL" series that are a true 9" radius, they say #4, but they are very short and tight and well made. Not sure about some of the Tomytec street switches, but most of the stuff they make is pretty good.
Tomytec makes some outstanding mechanisms for tight radius, because the pivot point for the powered truck is right on the universal and the worm is on the truck itself. Most conventional locomotive mechanisms are trying to twist the truck around and leave the worm fixed in the frame, and that can cause binding.
For what it's worth, the minimum radius for real streetcars is 50' !
July 21st, 2011, 02:29 PM #3
4" radius is VERY small. I have some Tomix Fine Track in that radius (103mm) and a 40' IM boxcar binds on that radius. The next step up is 5.5" radius and a 40' boxcar doesn't bind. Here's a link to a thread with some pictures:
Fine Track Small Radii
I run a MT FT on 8.5" radius Kato Unitrack at Christmas (all day, 5 days a week) and that has no problem at all. You might consider a Kato NW2 for tight turns.
I hope this helps.
July 21st, 2011, 03:16 PM #4
My 44tonner runs fine around 8 1/2" curves, but more than 5-6 boxcars (depending on weight) and it'll start slipping at lower speeds.
The B-Mann 70tonner, on the other hand, doesn't seem to like the tighter curves as much, and starts slipping way before the 44tonner.
The Kato NW2 can do anything. Period. (Well, I've had it pull a bunch o' boxes around 7"-8" short curves on flat surface before no problem).
The Kato Kritter (105-107) is able to go around some pretty sharp curves, too (at least 7"-8") but I haven't tried it yet while pulling anything.
Very short, sharp "bends" (where the actual radius is very tight but only a couple degrees of distance) are possible with all three, but you just have to watch the couplers (like RandGust said).
Remember, the engine itself does not have to go around the curve: there are plenty examples in real life where conditions like sharp radius or lack of support for heavy locos necessitated the use of idler flats or other cars as a "handle" to reach the car spots.
Google "Erie's Harlem Station" for a very groovy prototype & various models people have done off it.
(they used boxcabs, too )
July 21st, 2011, 04:40 PM #5
The only loco I get to go around 103/4in curves is the Atlas MP15. All
the other switchers could not make it around the curves without popping a truck.
I tested Kato, ConCor, Bachmann and Atlas switchers. Every thing works fine going around the 140mm/5.5in curves. You'd think the 70 or 44 tonners could cut the 103mm but they can't. Their older streetcars can though.
The biggest problem you will have is body mounted couplers. Unlike the real things Microtrains body mounts do not have the range to make the tight turns.
If you use truck mounted couplers you will have
fewer problems but you must go slowly. If you've seen any videos of
street running you know the train barely break 5 MPH.
Modifying the locos to be able to take the tight turns requires altering the pivotpoints. A little change could make a difference. But messing up here will destroy the chassis or trucks. You might swap an older body on the MP-15 chassis.
You might consider building a boxcab on a TomyTec TM-03 chassis.Cheap and Nothing Wasted
July 21st, 2011, 05:06 PM #6Confirmed TrainBoard Member
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- Feb 2010
I have the 44 tonner that I've been running it on Tomix Mini-Curve track. My findings are:
The 44 tonner can run on the R140mm (5 1/2") curves and switches but not the R103mm (4") curves; the trucks are actually quite limited in how far they can turn in relation to the body. The trucks on my newer Tomix DE10 (Japanese road switcher about the size of an MP15) have a lot more swing, letting it run on R103 with ease despite being a bigger model.
It will sort of do an R140 S-curve but I'm not convinced it is 100% reliable yet. Coupling is also an issue with tight S-curves.
As for rolling stock there seems to be a lot that can run on R140 but you really need to test specific manufacturers models and couplers. My Life Like and some Atlas and MT 40' boxcars work fairly well (A Life Like 50' reefer even works) but my newer Atlas 40' boxcars, like the new CP green paper car, bind on the R140 curves. My only MT caboose also binds despite being short. The Atlas beer can shorty tank cars run great, however even very short fixed 2 axle cars have a lot of trouble, the modern Japanese Wamu 80000 cars bind completely. Regardless of trucks nothing longer then 50' seems to work, though even that 50' reefer overhangs enough that someone could walk on the outside rail.
At the end of the day I would suggest spending $20-$30 on either the "Tomix 91081" MA starter set or if you really want to try 4" curves then the "Tomix 91080" SA starter. Both sets contain an oval of track and a Tomix tracker feeder cable (cut and strip the small end to plug it into your own throttle). The first set has R140 (5 1/2") and R177 (7") curves, the second has R140 (5 1/2") and R103 (4"). There is a US distributor who has this track now, though I can't mention the name obviously (use Google to find the product, they rank high on the search results).
July 21st, 2011, 05:28 PM #7Confirmed TrainBoard Member
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- May 2005
I will add to the concern about couplers.
Coupler position in relation to the centerline of your track will vary widely based on whether the coupler is truck-mounted or body mounted. I don't think you will be able to get a train which includes a truck-mounted coupler connected to a body-mounted coupler to navigate these tight turns.
And even if all your rolling stock (locos and freight cars) all use truck mounted couplers, there will still be a variation in coupler position in relation to the centerline of your track, based on the distance from the pivot point of the truck to the end of the coupler. Most loco trucks will have a longer wheelbase (and longer distance from pivot point to the end of the coupler) when compared to the small freight cars you will want to use for such a layout. Some of your rolling stock might have some flexibility in letting the coupler bend from side to side while in its mounting, while others might not. The coupling of your loco to the first freight car will probably be the most challenging.
July 21st, 2011, 06:16 PM #8
Excellent, thanks for all of the feedback! What I'm doing is planning out (may never build it, but maybe I will, we'll see) an urban industrial layout with a car ferry and tracks through streets, etc. I know my Bachmann PCC will do 3.75" (binds at 3.5) and wanted to see just how tight I could get the rest. Building a boxcab would be AWESOME (and I've already seen the Tomix and Kato small chassis that'll probably do the trick), plus I plan to use truck-mounted couplers (operations over rivets for me) and nothing bigger than a 50' car. My older Atlas, Con-Cor and Bachmann cars seem to be happy at that radius, and I don't mind having an idler flat in between where necessary. The main point is to be able to have it run in a crowded city scene, which it looks like it'll do. I've already drawn it up with 4" curves, and I'll go ahead and switch it to 5 or 5.5 and see how it looks. Here's what it looks like so far:
Anyway, thanks as usual TBers.
July 21st, 2011, 07:31 PM #9
OK, rebuilt with 5.5" curves minimum:
And looks like i'll finally have to hand lay a switch, MC! Either that or kitbash two switches and a crossing. :tb-tongue:
July 21st, 2011, 07:31 PM #10Confirmed TrainBoard Member
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- May 2005
That is a really interesting looking layout concept.
I think you can help yourself to allow some of your curves get a larger radius, while still keeping the overall plan the same, if you replace the turnouts shown currently (which *seem* to be standard size) with the short code 80 Peco turnouts which are 3.5 inches long on the straight side, and have a 9 inch radius turn (not 9.75) on the diverging leg. I have a few of these, and I find them to be very reliable turnouts. Just the reduction in length of the straight side alone will free up more space slightly wider curves.
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