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Loco speed mystery

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  • Member since
    September, 2010
  • 249 posts
Loco speed mystery
Posted by Mister Mikado on Sunday, June 02, 2019 11:23 PM

I lashed two proto 2000 e8 locos aa, end to end, to operate together. Because of a universal joint issue in the trailing unit, I had to disconnect the driveshaft at the cab end.  Motor power is only delivered to the rear truck--the front truck is now freewheeling.

I expected this unit to have half its power, but when I ran it and her companion on the same track, the compromised loco ran FASTER and ended up pushing the lead unit.  How in heck could this be?  They are identical models.  When the broken unit was intact they both ran at the same speed.

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Posted by Mister Mikado on Monday, June 03, 2019 2:26 AM

My apologies to all. I was mistaken, the locos are NOT identical. I swapped one of the chassis some time back for a newer run and this explains the speed difference.  I would appreciate feedback however on whether a loco will run just as well with the motor only hooked to one truck. -Rob

  • Member since
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  • From: Collinwood, Ohio, USA
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Posted by gmpullman on Monday, June 03, 2019 2:29 AM

Mister Mikado
I expected this unit to have half its power,

Half the tractive effort. The motor still has the same amount of power, now directed to only one truck. The motor no longer has the burden of driving the worm gear and associated loss from the friction of the grar train and bearings in the now disconnected truck. Thus on level track the speed will be higher with less drag on the motor.

What will change is the tractive effort (or factor of adhesion) on a grade.

Cheers, Ed

  • Member since
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  • From: Pacific Northwest
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Posted by SPSOT fan on Monday, June 03, 2019 5:15 AM

The real world did what you did in a way, EMD E units and ALCo PA had A-1-A trucks with an idler in the middle. I believe this was done to get the locos to go at faster, passenger, speeds. However this sacrificed the power of the locos on hills. Your model is dispaying the same thing.

Regards, Isaac

I model my railroad and you model yours! I model my way and you model yours!

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Posted by Mister Mikado on Monday, June 03, 2019 10:38 AM

Thank you, Ed and Isaac for your feedback.  Since this half-disabled loco is the trailing helper I will still get one and a half times tractive power on hills, no big deal since the load will be only 5 Athearn passenger cars.  Now to locate that part.  Seems you can only purchase it in a set called "Life-Like Proto 2000 E6 E7 E8 E9 Worm Gear and Spline Shafts", out of stock everywhere.  I only need the black yoke-shaped u-joint coupling.

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Posted by mbinsewi on Monday, June 03, 2019 10:58 AM

Mister Mikado
  I only need the black yoke-shaped u-joint coupling.

Not exactly sure what part you need, the spline drive shaft?  the end that goes to the flywheel? or the worm gear?

Check Ebay for parts, as you might be able to use Athearn parts.  Also, there are some P2K E8's over there that are going to decent prices.

Mike.

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  • From: Canada, eh?
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Posted by doctorwayne on Monday, June 03, 2019 12:11 PM

Mister Mikado
....Because of a universal joint issue in the trailing unit, I had to disconnect the driveshaft at the cab end. Motor power is only delivered to the rear truck--the front truck is now freewheeling....

While you don't specifically mention it, I have to assume that you've also removed the worm from the cab-end truck...otherwise, it won't be freewheeling, but rather the wheels will be sliding/skidding along the rails.

Wayne

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Posted by Mister Mikado on Monday, June 03, 2019 12:32 PM

doctorwayne

 

 
Mister Mikado
....Because of a universal joint issue in the trailing unit, I had to disconnect the driveshaft at the cab end. Motor power is only delivered to the rear truck--the front truck is now freewheeling....

 

While you don't specifically mention it, I have to assume that you've also removed the worm from the cab-end truck...otherwise, it won't be freewheeling, but rather the wheels will be sliding/skidding along the rails.

Wayne

 

Worm gear is out and cap snapped back on.  Thank you Wayne

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