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BLI HO Centipede - traction problem?

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BLI HO Centipede - traction problem?
Posted by Arto on Tuesday, October 22, 2019 6:00 PM

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?

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Posted by ATLANTIC CENTRAL on Tuesday, October 22, 2019 7:16 PM

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  

    

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Posted by gregc on Wednesday, October 23, 2019 5:35 AM

how much do your locos weigh?   

it doesn't matter how many drivers there are.

greg - Philadelphia & Reading / Reading

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Posted by ATLANTIC CENTRAL on Wednesday, October 23, 2019 6:21 AM

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.

Sheldon

    

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Posted by RR_Mel on Wednesday, October 23, 2019 8:26 AM

I agree with Sheldon on the ridged wheel base.  My Cab Forwards (4-8-8-2) pull great on my straight or slightly curved 3½% grade but have some wheel slip on my 30” helix.
 
My E7s don’t have any wheel slippage anywhere on my layout.  The worst slippage is my 4-8-4s.  They slip badly on my helix and no slip on the non helix grade, both are 3½%.
 
 
Mel
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by rrinker on Wednesday, October 23, 2019 7:21 PM

 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.

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Posted by KemacPrr on Thursday, October 24, 2019 12:42 AM

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 

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Posted by gmpullman on Friday, October 25, 2019 1:25 AM

Arto
I've pulled this same train with two BLI T-1 with no problem.

Curiosity got the best of me. Oranges and apples Confused

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

 

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Posted by ATLANTIC CENTRAL on Friday, October 25, 2019 6:22 AM

Which brings us to another question.

T-1? Reading? C&O? PRR?

Sheldon

    

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Posted by maxman on Friday, October 25, 2019 11:35 AM

gmpullman
Doubleheaded 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.

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Posted by gmpullman on Friday, October 25, 2019 11:47 AM

maxman
Regardless 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".

Regards, Ed

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Posted by Arto on Friday, October 25, 2019 12:16 PM

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

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Posted by gmpullman on Friday, October 25, 2019 5:00 PM

Arto
EDIT: 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

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Posted by railandsail on Thursday, November 7, 2019 6:02 AM

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,....

 


This back page ad from the  May 1984 issue of Model Railroader says it all.  PFM ran full back page ads in both Railroad Model Craftsman and Model Railroader for some 25 years ending in about the late 1980s.

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/

 

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Posted by NVSRR on Thursday, November 7, 2019 6:15 AM

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

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