 Joined: 20/08/2018(UTC) Posts: 157 Location: Geneve, Geneva
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Hi,
I am thinking of running a long Xmas train around the tree. With the extended set of wagons (35 so far, still growing ...) I'm afraid the loco I had in mind for it would not be able to pull them all.
On this line of thought, I was wondering if there is a formula to estimate how many wagons a loco can be expected to pull (on flat surface in this case)? Speed is not important for as long as it moves :)
I expect that the weight of the loco vs the total weight of the wagons is the main factor, but does the number of axles (powered for the loco and the total count for the wagons) matter as well?
How much does the curve radius impact this? I had some C-track R2 in mind for this. Would a larger R make a notable difference?
The loco weight doesn't seem to be ever mentioned on any of the manufacturers' web sites. If I were to look for a replacement loco for this purpose, do you know of a repository of information where the weight is listed?
Cheers,
.costin
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JMRI on RPi & DCC++ / C-track / Marklin, Roco, ESU, Bemo locos / Christmas car collector |
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Joined: 16/02/2004(UTC)
Posts: 15,452
Location: DE-NW
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Hi!
Things are complicated with respect to tractive effort of locomotives. There were cases of Märklin locos where removing or shortening a spring drastically increased the tractive effort. The spring mentioned here pressed an axle without traction tyres onto the track. Reducing the tension of the spring increased the pressure on the traction tyres.
Weight matters, but placement of traction tyres also matters. Some locos have unpowered axles that matter. And most important is the pressure on axles with traction tyres.
Many testers measure the tractive effort in grams. And there are rules of thumb to convert grams (tractive effort, not loco weight) to coach axles. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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 Joined: 04/02/2011(UTC) Posts: 3,570 Location: Paris, France
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Hi
There are many factors in play here:
- curves; they reduce the loco traction efforts (no differential) and increase the rolling friction of cars. So a larger radius is best
- gradient: above 3 to 4° the pulling power needed will drastically reduce the capacity to pull cars
- planeity of tracks: any vertical "knick" will cause the traction tyres to lose contact with the rail
- rail surface & tyres clealiness: a clean track with clean tyres (cotton swab with alcool) will increase traction.
Of course the type / manufacturer of the loco and cars will impact: Märklin locos usually have an excellent pulling power.
Recent cars with conic/needle bearings have almost zero friction.
So depending on the type, a Märklin loco can pull easily from 30 to 80 2 axle cars under optimal conditions
Cheers
Jean |
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 1 user liked this useful post by JohnjeanB
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 Joined: 01/03/2008(UTC) Posts: 2,883 Location: South Western France
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Originally Posted by: costing  Hi,
I am thinking of running a long Xmas train around the tree. With the extended set of wagons (35 so far, still growing ...) I'm afraid the loco I had in mind for it would not be able to pull them all.
On this line of thought, I was wondering if there is a formula to estimate how many wagons a loco can be expected to pull (on flat surface in this case)? Speed is not important for as long as it moves :)
I expect that the weight of the loco vs the total weight of the wagons is the main factor, but does the number of axles (powered for the loco and the total count for the wagons) matter as well?
How much does the curve radius impact this? I had some C-track R2 in mind for this. Would a larger R make a notable difference?
The loco weight doesn't seem to be ever mentioned on any of the manufacturers' web sites. If I were to look for a replacement loco for this purpose, do you know of a repository of information where the weight is listed?
Cheers,
.costin
Others have already given you very good advice, but why not just telling us which loco "you have in mind"? Between us we must have operated probably every single loco Märklin has made. If you say "3022" , I'd say go ahead you'll never stall it, if you say 3001 , I'd say 15 cars max Of course the condition of traction tires is the main factor! Key parameters: weight carried by the wheel and adherence coefficient. Tractive effort= weight on powered axles x adherence coefficient Metal on metal adherence coeff is 0.1, neoprene on metal is >0.8 For example : a 500 g loco with 4 axles total and only two powered axles (e.g. 3041) i.e half of the weight on powered axles. without tires 250 x 0.1 = 25 gr With tires 250 x 0.8 = 200 gr Hope this helps |
Jacques Vuye aka Dr.Eisenbahn
Once a vandal, learned to be better and had great success! |
7 users liked this useful post by jvuye
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Joined: 20/08/2018(UTC) Posts: 157 Location: Geneve, Geneva
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Thanks a lot for the numbers, it is much clearer now.
The loco I had in mind for this is a BR 24 (36243) (having added season-appropriate songs to it). It's relatively small (290g, w/ tender) with 1 traction out of the 3 powered axles. I'll try to add more weight to the boiler in preparation for this exercise.
Cheers,
.costin
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JMRI on RPi & DCC++ / C-track / Marklin, Roco, ESU, Bemo locos / Christmas car collector |
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Joined: 01/03/2008(UTC) Posts: 2,883 Location: South Western France
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Originally Posted by: costing Thanks a lot for the numbers, it is much clearer now.
The loco I had in mind for this is a BR 24 (36243) (having added season-appropriate songs to it). It's relatively small (290g, w/ tender) with 1 traction out of the 3 powered axles. I'll try to add more weight to the boiler in preparation for this exercise.
Cheers,
.costin
Ok, that easy to calculate then The loco is 290 g, and you'll find out that actually, on steamers, only two axles really carry the weight (usually the first front driver and the last rear) The other axles are ther for "show" and current conduction duties. So you probably have something like 130 or 140 g on each of the driving axle That's a tractive effort of (130 x 0.8 = 104 g) (with the tires) + (130 x 0.1= 13) (without tires) or somewhere probably near 115 to 120g of horizontal traction capability. That's pretty substantial in terms of cars/coaches, especially if you are properly maintaining their axles bearings . A nicely tuned car 2 axle will roll horizontally with 4 grams or less, easily! Double that for a 4 axle car. Now you can do the math! Have fun and Merry Xmas! PS: Un Suisse Roman sans loco CFF? C'est quoi ce délire?  |
Jacques Vuye aka Dr.Eisenbahn
Once a vandal, learned to be better and had great success! |
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Joined: 20/08/2018(UTC) Posts: 157 Location: Geneve, Geneva
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Great, you give me hope that it could actually work in the current form! Originally Posted by: jvuye PS: Un Suisse Roman sans loco CFF? C'est quoi ce délire?  Not being an actual Swiss I get a pass. I do have however a Re 4/4 II which would be better suited from performance point of view (having 530gr). But it somehow doesn't match the Xmas spirit :) Cheers, .costin |
JMRI on RPi & DCC++ / C-track / Marklin, Roco, ESU, Bemo locos / Christmas car collector |
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Joined: 01/06/2016(UTC)
Posts: 2,465
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Originally Posted by: costing Thanks a lot for the numbers, it is much clearer now.
The loco I had in mind for this is a BR 24 (36243) (having added season-appropriate songs to it). It's relatively small (290g, w/ tender) with 1 traction out of the 3 powered axles. I'll try to add more weight to the boiler in preparation for this exercise.
Cheers,
.costin
Why not 2 locos by a double traction? Or a Swiss Croc?  For example, my new Insider Shunting Croc Ce 6/8 II has 6 powered axels by 2 motors for 2 boogies with 6 powerd wheels and 2 traction tires at each boogie.   Should be enough to pull your train "all around the Matterhorn" . The Swiss have nice and strong locos. Happy X-mas. Regards TEEWolf
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2 users liked this useful post by TEEWolf
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Joined: 20/08/2018(UTC) Posts: 157 Location: Geneve, Geneva
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You are right, there are many other nice alternatives. Just that I imagined this train to be a steam one, puffing smoke around the tree. And this is the only steam I have so far. Worst case I'll put the Re 4/4 II instead, has both powered axles with traction tires. Or the Roco BR 103, that's another strong one. Now, back to the BR 24. The boiler space is pretty well packed but there were still corners where small screws and nuts could fit (6g). A larger piece of lead (14g) went below the cab's roof, on top of the traction tires. So 20g in total, not bad... Cheers, .costin  |
JMRI on RPi & DCC++ / C-track / Marklin, Roco, ESU, Bemo locos / Christmas car collector |
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 Joined: 22/01/2009(UTC) Posts: 14,875 Location: On 1965 Märklin Boulevard just around from Roco Square
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If you go down that route why not open the boiler and see if anything fits into the boiler , at least its not visible so long it doesn't interfere with any metal components. here is a video from my older version BR 24 with sound |
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1 user liked this useful post by river6109
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Joined: 20/08/2018(UTC) Posts: 157 Location: Geneve, Geneva
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It only helped with a few grams, not too much volume left in it to fill. Today I've taken all cars out for a ride, and the BR 24 managed to pull 1.5 kg in the form of 24 cars (21*2 + 3*4 axles). Now I get where BR 24 comes from @jvuye, you were spot-on with the calculations, subtracting the tender weight the above is in line with your estimates. Kudos! I've switched locos to the heavier ones to test the limits but then I started having uncoupling accidents. Probably because I didn't arrange them correctly, and some were very light (27-30g) while others up are up to 100g, so they were pulling the lighter ones off track. I wrote down all the individual weights so next time I'll try sorting them by weight (as opposed to kids' preferences like today). Until then you can see the Marklin Xmas wagons and Roco locos in action here, with the steamer playing happy songs on the side. Happy holidays! .costin |
JMRI on RPi & DCC++ / C-track / Marklin, Roco, ESU, Bemo locos / Christmas car collector |
1 user liked this useful post by costing
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Joined: 01/03/2008(UTC) Posts: 2,883 Location: South Western France
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Originally Posted by: costing
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@jvuye, you were spot-on with the calculations, subtracting the tender weight the above is in line with your estimates. Kudos!
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Thanks but "spot on" maybe a little too much! This is simply "off the cuff approximate science"! Happy Holidays! Edited by user 27 December 2018 18:02:12(UTC)
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Jacques Vuye aka Dr.Eisenbahn
Once a vandal, learned to be better and had great success! |
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