12 wheel drive locomotives

[gandy dancer#1]

HI: was wondering about these,saw one by bachman new in box are these god units? will they pull a few cars?? i would assume being 12 wheel drive, means 3 motors?? also can you buy un painted  bodies for locomotives and paint them to suit your self??

[ACY]

12 wheel drive in this case means one motor and two powered 3 axle trucks. The Union Pacific DD40AX Centennial is the only recent Bachmann HO loco with 2 motors, none have 3. It requires 22" radius, but looks bad even on 24" radius and sometimes does not like 22" radius depending on which version you have.

[bobwrgt]

In real life 12 wheel drive might mean more pulling power and more motors. In model trains this is not so. Pulling power is more a matter of weight to designed gear ratio. Most all model trains have one motor. Athearn made a DD40 with two motors. Even with 2 motors if they don't have enough weight you would not get better pulling. You would get better electrical pick up if all wheels have wipers. Look for undecorated models if you want to do your own paint and lettering.

Bob

[jward]

bob that is not true.

if you have any doubts consider this. most 12 wheel (6 axle) diesels are considerably larger than their 4 axle counterparts. this is especially true for the more modern diesels some of which are HUGE. it goes without saying that longer chassis equals more weight, thus more pulling power. you can prove the wieght for yourself using a postage scale, and if you have grades on your layout you will definitely notice the difference.

example, i used to run an iron ore train of 13 cars plus caboose. it required 3 athearn gp35s to get to the top of the mountain on 4% grades, butonly 2 6 axles of any type to do the same. i mostly ran it with gp35s beacuse the 6 axles don't play well with shorter cars.

if you want to do a true comparison of whether the extra wheels make a difference in pulling power, remove the weight difference from the equation. compare the pulling power of an atlas rs3 with an atlas rsd5. the only real difference between the two is the trucks, rs3 is 4 axle, rsd5 is 6 axle.

[bobwrgt]

Athearn GP35's are light to start with. Small frame and small fuel tank. The other Athearn GP's like the GP50/60 have more weight with larger frame and fuel tank. They would have pulled your train with only 2 units. They all have the same 4 wheel trucks and motor drive.
What i am getting at is you just can't assume that 6 wheels will pull more with the same weight as a 4 wheel truck engine. You have to evaluate each engine on it's own design.
AHM, IHC, Rivarossi, and Model Power make light 6 axle engines that don't pull that well. Some of them were 6 axle but only had 4 axles powered with one set of wheels floating in each truck.
The Athearn SD40-2 will out pull the Bachmann SD40-2 because of it's design, both are 6 axle.
The Atlas SD24/35  is 6 axle but won't compare to larger 6 axle engines with more weight.
The original question did not mention scale. Could be HO or N scale. The N scale Atlas RSD5 only had 4 axles powered and one idol in each truck. This created drag and took weight away from the other axles.
The best pulling HO Bachmann is the E33 because of it's weight.

BoB  

[jward]

i was referring to the ho scale models. i had a number of the rsd5s in n scale, as you said they had only 4 axles powered but operationally they were similar to my rs3s and vastly superior to the kato rs2.

athearn gp35s are light, but i hadn't noticed enough of an increase in pilling power in the gp38-2 gp40-2 or gp50s to allow for 2 units on this train. all my athearns had been regeared as well which did increase pulling power slightly, but once again not enough to allow the use of only 2 units.

it should be noted that differences in pulling power are not that noticeable on level track, but once you have grades on your layout the differences become painfully apparent.

i will grant that many locomotives to-day are much heavier than locomotives of 30 years ago. but among locomotives of the same manufacturer, you will find that the 6 axle locomotives will pull more as a general rule than their 4 axle counterparts. you could add weight to a 4 axle so that it will outpull an unweighted 6 axle, but add the same weight to the 6 axle and it will once again outpull the 4 axle.