Loco Power - Motor or Weight?

[Nearholmer]

PS to previous: The Alco RSD1 was a Co-Co derived directly from the RS1 Bo-Bo. It was a lower axle-weight version, for military use. The first RSD1 were for a very steeply-graded, low-speed route, and they had a better low-speed TE than the originals, but exactly why they chose to make it a Co-Co, rather than do the obvious and make it an A1A-A1A, I don't know ......... it may have been adhesion, or it may have had something to do with the thermal rating of the motors not being up to prolonged operation at full-load at low speed.

[AndyID]

7 minutes ago, Nearholmer said:

PS to previous: The Alco RSD1 was a Co-Co derived directly from the RS1 Bo-Bo. It was a lower axle-weight version, for military use. The first RSD1 were for a very steeply-graded, low-speed route, and they had a better low-speed TE than the originals, but exactly why they chose to make it a Co-Co, rather than do the obvious and make it an A1A-A1A, I don't know ......... it may have been adhesion, or it may have had something to do with the thermal rating of the motors not being up to prolonged operation at full-load at low speed.

 

Thanks for that. I vaguely remember reading about it somewhere.

 

The Co-Co version would be more suitable for lighter weight and less well-laid track while not reducing maximum traction compared to the Bo-Bo. An A1A-A1A version would only be capable of producing around 70% of the maximum traction produced by the Bo-Bo and the Co-Co versions.

[AndyID]

50 minutes ago, Nova Scotian said:

Again, this is only when you assume the coefficient at the rail is consistent and even.

 

 

True and I think it's a quite reasonable assumption. If there is any lubricant on the rails I'm pretty sure a passing train will do a good job of distributing it evenly.

[AndyID]

On 13/02/2021 at 16:09, AndyID said:

The number of driven wheels makes no difference to the adhesion. You can convert an 0-10-0 into an 0-4-0 and it will pull just as well. (I expect someone will object to that last bit  )

 

 

Perhaps I should amend that to read "many people"

 

I didn't think it would be quite so controversial but clearly that was an underestimation on my part. Despite that I'm sticking to my guns - or to be more accurate I'm sticking to Guillaume Amontons' guns. The poor guy only made it to 42.

 

 

[Mark Laidlay]

I watched reviews of various US diesels (models) and number of axles made no difference.  I see manufacturers claiming to have fitted a new more powerful motor then fools buying them who complain that they won't pull a b bigger train than the last version.  Surely there is a UN body who can unilaterally declare that changing the motor won't help so manufacturers need to stop making claims of such.

[DCB]

On 14/02/2021 at 00:09, AndyID said:

Gearing affects max and min speeds and the torque (turning force) but adhesion is only a function of weight on the driven wheels and the coefficient of friction between the wheels and the rails. As you correctly say that depends on the materials and any contamination on the surface.

 

The number of driven wheels makes no difference to the adhesion. You can convert an 0-10-0 into an 0-4-0 and it will pull just as well. (I expect someone will object to that last bit  )

 

I posted on another thread, but when I experimented with two near identical OO Gaiety Panniers I found that when I loaded them to the maximum double heading I was able to put one on top of the other and it then pulled the same load, albeit it needed a higher power setting.   That was on Peco code 100 steel track with Peco N/S points and it didn't bother it much whether crossing points or on plain track.

The H/D chassis has a single start worm, I guess its about 30:1 That lets the engine start with that load. The equivalent Triang / Hornby 0-6-0 chassis has a two start worm and wont start the train when ballasted down to the same weight unless you slacken the couplings and take a run at it, even then it isn't happy.   Bachmann, er I'll let someone else wreck their Bachmann chassis, but the Bachmann 57XX only hauls half as much as the Gaiety so 4 times the weight should strip the gears.

[Nova Scotian]

5 minutes ago, DavidCBroad said:

I posted on another thread, but when I experimented with two near identical OO Gaiety Panniers I found that when I loaded them to the maximum double heading I was able to put one on top of the other and it then pulled the same load, albeit it needed a higher power setting.   

To make it fair they should have their own onboard power supply. Running them as they are off track power is going to change the result

[Nearholmer]

One of my friends who is, like me, into old-fashioned-style 0 gauge conducted a great series of haulage tests on his layout, which has a terror of a long gradient, which is straight, but runs in and out of quite tight curves which impose a lot of drag at top and bottom.

 

Naturally the weight of locos hugely affected hauling power, but the biggest lesson was in terms of coefficient of friction, in that he demonstrated very clearly what a huge difference the materials used for the wheel-tyres made. The winner, on a tractive effort to weight ratio basis (that was selected as a way to even things out between huge and tiny locos), was a loco with turned cast-iron tyres. Locos with plain sintered wheels did pretty well, and the losers were locos with stainless-steel or bright-plated wheels, both of which slipped terribly with quite light loads.

 

The track, incidentally, was nickel-silver rail. On steel, the iron wheels would probably have done even better.

[DCB]

Duplicate

 

 

Edited February 15, 2021 by DavidCBroad

[kevinlms]

On 15/02/2021 at 09:30, Nearholmer said:

PS to previous: The Alco RSD1 was a Co-Co derived directly from the RS1 Bo-Bo. It was a lower axle-weight version, for military use. The first RSD1 were for a very steeply-graded, low-speed route, and they had a better low-speed TE than the originals, but exactly why they chose to make it a Co-Co, rather than do the obvious and make it an A1A-A1A, I don't know ......... it may have been adhesion, or it may have had something to do with the thermal rating of the motors not being up to prolonged operation at full-load at low speed.

The Victorian Railways B Class, was the first GM EMD excursion into Co-Co territory and proved to be highly successful.

 

https://en.wikipedia.org/wiki/Victorian_Railways_B_class_(diesel)

[AndyID]

27 minutes ago, kevinlms said:

The Victorian Railways B Class, was the first GM EMD excursion into Co-Co territory and proved to be highly successful.

 

https://en.wikipedia.org/wiki/Victorian_Railways_B_class_(diesel)

 

Clyde Engineering. Yeah! Good to hear the name survived in Australia.

 

(Sadly the shipyards on the Clyde sort of lost their way due to factors financial and political. A very complicated story but sad nonetheless.)