I'm running a pair of HO Broadway Limited Centipede pulling a 36 car freight (reefer) (just assume all Athearn blue box), 2.5% uphill grade, 30"+ radius curve. They can't pull it.
I've pulled this same train with two BLI T-1 with no problem.
With all those axles/wheels I would think the Centipedes would pull this. Install traction tires?
Arto I'm running a pair of HO Broadway Limited Centipede pulling a 36 car freight (reefer) (just assume all Athearn blue box), 2.5% uphill grade, 30"+ radius curve. They can't pull it. I've pulled this same train with two BLI T-1 with no problem. With all those axles/wheels I would think the Centipedes would pull this. Install traction tires?
Your problem is simple, if that grade is fully or partly on that 30" curve, you are loosing traction and adding resistance when the loco is on the curve.
The rigid wheel base of the Centipede means more resistance in a curve. And with models, the same total weight spread over more drivers generally means poor pulling power.
And if the transistions in and out of the curves do not have easements, and if the vertical changes are not gentle with good easements, the loco is loosing lots of traction at those points as well.
While it may travel around 30" radius fine, that is way to sharp for a Centipede to perform well.
Do your T-1's have the traction tire driver installed?
Sheldon
how much do your locos weigh?
it doesn't matter how many drivers there are.
greg - Philadelphia & Reading / Reading
gregc how much do your locos weigh? it doesn't matter how many drivers there are.
Actually, the physics of the prototype does not scale down. Some detailed testing I did years ago showed that generally a 20 oz 4-6-2 would pull better than than a 20 oz 2-10-2.
And that rigid wheel base has a big effect on grades and curves.
Diesels pull better than steam because all the weight is on 4 or 6 axles that are not really effected by rigid wheel base friction or uneven track factors.
But the centipede is a diesel with a steam loco type rigid wheelbase and too many drivers, giving each driver not enough weight for good adheasion.
Some locos benifit from sprung drivers, I don't know what kind of suspension if any the BLI Centipede has, I suspect not much of one.
I don't know what the Centipede weighs, I don't own any, but I do own BLI T-1's. They are heavy and they have traction tires, they pull very well with all that weight on only 4 axles.
I think the Centipedes are fairly hefty models - it's as Sheldon says, the long rigid wheelbase is causing either binding and extra drag, or causing some of the driven wheels to break contact with the rail, reducing pullign power one way or the other. You could probably set up a test track with straight track and put an equivalent load behind the locos and see if they could pull it up the same or steeper grade if it were straight - I have a hunch they will.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
While the Centipedes have a number of axles only six per unit are doing any pulling. The lead and trailing trucks are there for the ride and the inboard axles of both 4 axle trucks are not geared . So running a A-A pair as the PRR did you have the same number of powered axles as a pair of SD-9's. With the weight spread out over non powered axles tractive effort will be less than a pure six axle unit. ----- Ken
ArtoI've pulled this same train with two BLI T-1 with no problem.
Curiosity got the best of me. Oranges and apples
Dynamometer test:
Setup, Ohaus spring scale anchored to roadbed,
DB_Baldwin2 by Edmund, on Flickr
Centipedes, 8 ounces of drawbar pull at 50% throttle, wheels slipping.
DB_Baldwin1 by Edmund, on Flickr
DB_Baldwin by Edmund, on Flickr
Doubleheaded T1s with traction tires, 50% throttle, wheels slipping:
DB_T1s by Edmund, on Flickr
DB_T1a by Edmund, on Flickr
17.5 oz. drawbar pull, wheels slipping.
Regards, Ed
Which brings us to another question.
T-1? Reading? C&O? PRR?
gmpullmanDoubleheaded T1s with traction tires, 50% throttle, wheels slipping:
How did you get the drives to slip with traction tires? Regardless of how you managed it, I don't think it's a good idea. One of the club members had a BLI something or the other get stalled in a tunnel because one of the cars in the train caught on something.
Since the loco was hidden, the natural reaction was to increase power until it became obvious that the engine wasn't going to come out of the tunnel.
It was then found that the increased power had spun one of the traction tires off the driver.
maxmanRegardless of how you managed it, I don't think it's a good idea.
It was slipping only long enough to take the photo of the spring scale. They will eventually slip and on tangent track at least there aren't any tendencies to "string-line".
Thanks Ed. That's exactly what I was hoping to see (and have someone post it).
I guess I'm going to have to look at getting one of those at the Milwaukee Trainfest. Or is that just some ordinary scale adapted for this purpose?
EDIT: I see that is an ordinary spring scale. The problem seems to be finding one that reads in ounces instead of grams and newtons.
Art
ArtoEDIT: I see that is an ordinary spring scale.
There's this:
https://tinyurl.com/y68tj7vh
I have one in my shopping basket. Might just click "buy now".
Cheers, Ed
Interesting Traction Posting
I was just reading about this impressive auction that will be occurring with a big brass collection. Within the documentation there was this presentation. I'll provide the link, but I also thought it would be worthwhile posting this portion as it may disappear after the auction finishes,....
The next and unique feature is the Tenshodo proprietary TPE ( Three point equalized) suspension. It’s a sophisticated system of levers that interconnects adjacent wheel sets and the lead and pilot trucks assuring equal contact pressure of every wheel upon the rail. Going over a rail joint gives a uniform click for each wheel. The back page of the 1984 issue of Model Railroader has a sketch and force diagram explaining the system as applied to a JNR C61, the first in 1982 to receive it. And also showing the arrangement on a GN Q-1 2-10-2, the first US prototype the use it in 1984. Power for both the Q-1 and Niagara is supplied through a torque arm idler gear box and a Canon red cap instrument motor. The Niagara has directional light just to the locomotive. The tender has sprung wheel sets on the five axle pedestal bed.
https://jimwalshcollection.com/tenshodo-nyc-niagara-1985-run/
Brian
My Layout Plan
Interesting new Plan Consideration
Didnt the prototype centipede have the same issue? Low TE because of all the wheels? I know they had the revolutionary idea of interch ngable power packs
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
Well, well, well. Wonders never cease!
Broadway Limited had a somewhat surprising (to me) solution to the Centipede traction issue.
The pilot and trailing trucks are sprung. Apparently the springs can cause a small amount of lift from the pilot and trailing trucks, enough to slightly lesson traction under difficult conditions. They suggested removing the two phillips head screws (part #97 on the exploded view diagram) and tightening the flathead screw all the way down and then backing off a turn.
It worked! Traction did improve. Unfortuneately not quite enough. They then said to tighten down some more but make sure the trucks still swivel freely. I tightened the flathead screw all the way down & backed off 1/4 turn. That improved traction some more, but not quite enough. I could get the train moving upgrade again by increasing throttle to 40%. It wouldn't even budge at full throttle before doing this.
Ultimately I decided to just get a third Centipede ( a demonstrator unit to go with the the two PRR). All is good now.