Key Imports L4-b Mohawk minimum radius?

[hunter_alexander]

Does anyone have a Key Imports brass L4-b Mohawk that they can test or tell me the absolute minimum radius it will negotiate?

I know Marks (spookshow) website says 11" radius, but then he mentions that anything below 19" radius his derailed the drivers.

I have one and before I go spending on track or making a definite plan, I would like to know what operationally I need to adhere to on curves.

Thanks in advance.

[mmagliaro]

Actually, Mark's web page on this engine specifically says that it cannot negotiate curves with 11" or sharper radius, so I'd say 11" is out.

My guess is that 18" or 19" would be the minimum.   An easy way to find out (and so you'd have a test fixture for the future),
would be to just buy a few packages of Kato Unitrack curves in 13-3/4", 15", and 19" radii, so you can set up test circles. 
 

[hunter_alexander]

Thanks Max. I will have to do that. I was just hoping that I could get away with 15" and 16" as minimum. Guess I will see.

And yes, I had no plans for 11" lol

[Norway2112]

I had one and it easily handled 18" radius curves on my layout.  So you can save and not buy the 19" KATO curves, but I agree with max, that would be a good and inexpensive way to test.  Not just drivers, but if my memory serves me well, check clearance of cab corners on the tender too in curves.

[randgust]

The late, great Verne Niner and I both had Hallmark ATSF 4-8-4 northerns.  And neither of us could run them on our layouts.

Motor, drive train, and four flanged drivers look identical to the Spookshow shot of the Key 4-8-2.

Verne actually WIDENED the gauge of his Peco C55 flextrack on the curves by filing the inner rail thinner after he had laid and ballasted it, which sounds nuts, but it worked. 

I did the opposite attack, which was to blind the two center driver sets by filing them off while under power on the workbench, which is equally nuts, and also worked.   I also put in brass and styrene shims to take up all the lateral motion on the lead and trailing drivers.  My mainline curves are 13" and 15".

edit:  hey, I found it, via google.  Atlas forum search didn't work at all:
http://forum.atlasrr.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=13587


I'm running mine through 11" curves now without issue.   You've got to be really frustrated to try this but what can I say - it spend two years in the display case before I did it....  Verne and i did a joint thread on the old Atlas forum about it, can't find it in the archives.  I've got good photos of what I did if anybody cares.

[nstars]

Our L4b runs without any problem through an 18" curve. I do also believe it runs through the 15" curves of the branch line, but I have to check that when I'm at home. My personal feeling is that it would not look great on an 11" curve as the overhang becomes significant, so I would recommend not to use such a small radius curve.

Marc

[eric220]

Most of the longer wheelbase Key stuff that I'm familiar with can handle down to a 15" radius. That's a hard 15"; 14.95" will cause a derailment.

[hunter_alexander]

Thanks everyone. I was hoping a 15" to 16" radius would work. I don't want to go smaller than that anyways.

If a definite hard 15" is it, then I will go with 16" on my plan.

[randgust]

My experience with the Hallmark northern was that my 15" curves had just enough irregularity in flex track to derail it, and my impression would be that the "14.95" comment is right-on.   And it was only the powered wheelbase, nothing else (not even those tender trucks) that got it.  So keep your fingers crossed with 16" and lay really, really, good and consistent curves.

[mmagliaro]

The Hallmark/Samhongsa 4-8-4 Northern and 2-10-4 are notoriously some of the most radius-demanding brass engines I've
ever seen.  Neither could make it around an 18" curve.  The 2-10-4 needs almost 20" to avoid binding or derailing.
There is just not enough lateral play in the drivers to accomodate anything tighter.

They are also very difficult to alter because the axles are run through 1-piece frames with the drivers then pressed
onto the ends.  That is, you cannot just take off a cover plate and drop the axles out.  They are run through holes, not through U-shaped channels.   And it is extremely difficult to press the drivers off.  I little trying told me that
the damage potential was too high to risk it.  They are either extremely tightly pressed on, or affixed with some kind of
Loctite.

I fixed the two I had by actually running the drivers and slowly machining off some of the backs of the driver rims with
a sharp Xacto blade running against the metal to allow for more lateral play (it took hours).

I don't have a Mohawk, so I don't know if the frame/axle arrangement is the same.  But if it is, and that engine
can't make it around the curves you want to run, don't plan on modifying the mechanism,
because it will probably be very difficult.   Widen the curves.

[hunter_alexander]

Max,

The Key Mohawk has drivers that have bearing blocks, sprung and fit into bearing notches in the frame. So the drivers are easy to replace.

I don't think I would ever mod the locomotive by any of the methods listed in this thread. Im just going to test and go with the proper diameter curves needed for it.

Thanks all.

[nstars]

Checked the L4b at home and It ran perfectly through a 15" curve without any hitch. Ps our PRR J1 does also go through the same 15" curve, but that is not a Samhongsa engine. We did have a Samhongsa ATSF 2-10-4, but we only tested it on our 18" main line and that worked without any problem. I do have to mention that our curve are very precise,as we used Peco tracksetta jigs to assure the radius of the curves.

Marc

[Norway2112]

Marc,

I have several Hallmark 4-8-4's and 2-10-4's and regularly run them through my 18" curves too without any trouble without any modification to the engine.  Most of my roster is brass so when making my layout I spent a great deal of time on not just the track but also a perfectly flat and even roadbed by planing and sanding the cork before putting track down.  Then using jigs put my curves in.  All of my brass engines from a 4-6-2 to 4-8-8-4's and 4-10-2's smoothly glide through the curves.  The really important thing if you run right radius curves is to make sure they are perfect and a constant radius, this is best achieved wit the track jigs/templates available in multiple radius sizes and straight.

[Cajonpassfan]

Marc,

I have several Hallmark 4-8-4's and 2-10-4's and regularly run them through my 18" curves too without any trouble without any modification to the engine..........The really important thing if you run right radius curves is to make sure they are perfect and a constant radius, this is best achieved wit the track jigs/templates available in multiple radius sizes and straight.

Bingo! My experience exactly, on 18" "ruling" radius, although I did have to tweak my Hallmark Northerns' pilot trucks slightly. Using the "tracksetta" templates makes all the difference... I don't own a Texas 2-10-4, so I don't know...but my  4-8-4's do fine...
Otto K.

[nstars]

Marc,

I have several Hallmark 4-8-4's and 2-10-4's and regularly run them through my 18" curves too without any trouble without any modification to the engine.  Most of my roster is brass so when making my layout I spent a great deal of time on not just the track but also a perfectly flat and even roadbed by planing and sanding the cork before putting track down.  Then using jigs put my curves in.  All of my brass engines from a 4-6-2 to 4-8-8-4's and 4-10-2's smoothly glide through the curves.  The really important thing if you run right radius curves is to make sure they are perfect and a constant radius, this is best achieved wit the track jigs/templates available in multiple radius sizes and straight.

I agree. The trick is to have perfect curves. Most peoples 18" curves are not perfect and could have points where the radius would be much less. Even a cork roadbed could pose a problem due as it can deform. We started using thin plywood as a roadbed and that works flawless with all the loco's we have.

Marc