THESE NEW SD 40 2S....

soo, whats the poop on these sd 40s??? are they worth thier pricetag?? can they pull any better than the gp s? i personally havent bought one myself,, im hoping a CP or CN version comes out soon,, but i really want to know,,, are they great? any probs we should know about? and what about tight turns? canada mike:woohoo:

Canada Mike, they are better than the geeps. I think they should pull better than the geeps but havent done a test yet. Having too much fun running them, but I expect them pull better because they are heavier. They are also much quieter thank to a new low friction gears and bushings. My only complain its a bit hard to convert to dcc. On tight turns, you should have no problems if you run 195mm and higher. Joe say they should run as tight as 160mm.

liltoot wrote:

,, im hoping a CP or CN version comes out soon,, :

Mike,
Rumor has it that there will be CN and CP available, each in two paint schemes.

Now we just have to wait:(

Jerry

Mike,

There is sd with a CP paintjob on that auction site that shall not be mentioned. Its a one off so it'll be higher than sticker price but, it'll give you an idea of what they'll look like. Hope that helps.

awesome!! with the extra weight n set of wheelsets,, they should be a better climber. i still have my first ho sd40, from athearn, then in my n days i had to buy a dozen katos,still have everyone,boy they glided like gold!!! best engine i ve ever seen!! and now i m in z, awaiting my first CP OR CN,,i m buying easyily a dozen of these!!! just to have laying around. I M STILL A STEAMER FAN,,own every steamer marklin has ever put out!! and a few azls, and aspen models:woohoo: as well. but in time, i ll have to run those SD40S atleast once a week!!! canada mike

The SD40-2 is not a great deal heavier than the GP's; 45 grams versus 40 grams. Seems to be able to pull a few more cars than the GP models, but certainly not a huge difference in capacity. Runs smooth and quiet. Had no problems on 195mm radius track or switches. MU's nicely with the GP's

cheerz Garth

garthah wrote:

MU's nicely with the GP's

That's the BEST news that I heard so far. This is the first report of MU's with the older GP's.
Thanks!!!
Bill Mock

Bill, mine runs very well with the last run of SD70s which are faster then the first run. I do run dcc, but I didn't touch the speed table.

Thanks John. I was really wondering if the new SD-40's could be MU'ed to locomotives of different types. This will make great photographs and videos.
Thanks! Bill Mock

I've heard that on each truck the center axle is slightly higher (furthermore than beeing flangeless). Is it true? Is that axle completely off track? When passing on a joint does the loco say "clac-clac .... clac-clac", or "clac-clac-clac .... clac-clac-clac"? I'm just wondering for close picture taking.

Anyway as a BN sample is available I'm just going to count my pocket money now.

Dom

Dom,

Correct, the middle axle is raised on each truck. Also it is flangeless. The SD40-2 is a very quiet runner. I am very pleased with it's performance in my testing. But I think it could use the extra electrical pickup of six wheels on the track instead of four per truck.

Rob

Rob, I want to change the middle wheel to a full size one. I want test my hyphotesis that a six wheel drive is better puller then a four wheel drive. I have a fairly small layout, so I want to see how the full size wheel its going to effect the running characteristics. The SD70 goes though my layout very well, So I hope the SD40 with six powered axle does the same.

shamoo737 wrote:

Rob, I want to change the middle wheel to a full size one. I want test my hyphotesis that a six wheel drive is better puller then a four wheel drive. I have a fairly small layout, so I want to see how the full size wheel its going to effect the running characteristics. The SD70 goes though my layout very well, So I hope the SD40 with six powered axle does the same.

Replacing the center wheels probably won't make any difference. If the axle is raised, then the wheels won't make contact with the rails. The only way to gain any traction from the center wheels is to modify the truck frames.

David, I have though about the height issue, and I got it cover. I have some wheels that are cut down for traction tires. I will use those if theres height problems. Thanks for the hint.

You have to remember guys, traction force is based on friction between the wheels and the rails. The friction is based on pressure (psi). The locomotive weight stays the same with 8 wheels or 12 wheels (p). But more wheels means more contact area (si). Same weight over more area equals LESS pressure (psi). Less pressure could mean less friction and therefore less traction force.
This is assuming a perfect world with all 12 wheels touching.
In the real world, probably only 6 or 7 of our 8 wheeled locomotive are touching at any given time. If you have 12 powered wheels, 6 per rigid truck; how many are really going to have tractive contact?
Now, if we had suspension like the big boys do; we could get all 12 wheels equal pressure and could rely on them for full tractive power.
Adding the drive gear to power the middle wheel with the same little motor may yield LESS power due to the friction and mechanical losses caused by all this new drive assembly.
But it sure is worth playing around with.
So, who's going to play? Because I want to know how it works.
Good luck to all!
Bill mock

BillMock wrote:

You have to remember guys, traction force is based on friction between the wheels and the rails. The friction is based on pressure (psi). The locomotive weight stays the same with 8 wheels or 12 wheels (p). But more wheels means more contact area (si). Same weight over more area equals LESS pressure (psi). Less pressure could mean less friction and therefore less traction force.

Rail adhesion is the key factor. For any locomotive, at some point wheels will slip because adhesion is overcome by power. More wheels on the rail means better adhesion for the same size of locomotive (and also distributes the weight more evenly to prevent damage to the track). Hence, more wheels will not reduce pulling power.

The maximum tractive effort cannot exceed the tractive mass times the coefficient of friction. If a vehicle attempts to supply more force, this will cause wheel spin. en.wikipedia.org/wiki/Tractive_force

This is why the steam locomotives built for hauling coal trains had so many drivers: the Virginian had 2-10-10-2s that were physically smaller than the famed 4-8-8-4 Big Boy, but hauled mountains of coal. They also could not go any faster than 15 mph because of the inertia of the huge (6 foot) low-pressure pistons, but then, as a priority, tractive effort trumped speed.

For a diesel locomotive, the tractive effort is equal to the stall torque of the individual traction motors, one per axle, added together. More traction motors equals more torque, and hence more pulling power.

In the model world, these differences become almost trivial, because we're dealing with fractions of an ounce as opposed to thousands of tons; plus, the wheels are all powered by the same motor. What isn't trivial is the potential for improved electrical pickup. Even if only four wheels per truck are in contact at once, the other two wheels can provide a possible gain when negotiating uneven trackage.

BillMock wrote:

In the real world, probably only 6 or 7 of our 8 wheeled locomotive are touching at any given time. If you have 12 powered wheels, 6 per rigid truck; how many are really going to have tractive contact?

More like only four wheels per truck will be in contact, particularly if the center axle is raised.

BillMock wrote:

Now, if we had suspension like the big boys do; we could get all 12 wheels equal pressure and could rely on them for full tractive power.

Exactly right. Real trucks are equalized so that all wheels are in constant contact with the rails. This is not an option in small models.

BillMock wrote:

Adding the drive gear to power the middle wheel with the same little motor may yield LESS power due to the friction and mechanical losses caused by all this new drive assembly.

I strongly suspect that the amount of added friction of an extra gear probably won't put any measurable dent in pulling power.

It still comes down to the height of the center axle. Putting traction tires on the center wheels will be a gamble that can play out in a number of ways.

If the traction tire is too thick, it can raise the center axle and lift other wheels off of the track, which would interfere with electrical pickup even if it does improve pulling power, and might also give rise to potential derailments.

If the traction tire isn't thick enough, it won't do anything.

Getting the traction tire exactly the right thickness depends on knowing the precise offset of the center axle, and mechanical slop would probably introduce enough error that all bets would be off regarding what it does.

This is not to say it's not worth trying; I'm all for it! I'm just playing devil's advocate by offering up some experiences from working in N scale.

Excellent points David.
My main concern would not be the tolerances of the wheel heights and diameters, etc. which could be measured in microns but how these would play out on my poor track tolerances.
On your track, I have NO concerns. On my layout, that's another story.
But having ALL 12 wheels for electrical pickup; a MUST for DCC, I'd imagine.
I can't wait to see the modified engineering schemes to come. This is going to be fun and could produce some revolutionary designs for future Z scale locomotives.
Go to it guys!!!
Bill Mock

sorry,, did not know this??!!! your saying the center set of wheelsets DONT DO NOTHING!!?? THEY RE FOR DECORATION ONLY? with no electrical pickup, nor traction? this is news to me,, and unhappy news at that. please say your messing with my head! canada mike

liltoot wrote:

DONT DO NOTHING!!??

Huh?
I cannot comprehend double-negatives.
Is your meaning, "Do not do any thing?" or "Do nothing?"

Alex

Tokyo, Japan

Alex, its simple. Two negatives makes a positive, just like math. when somebody says, I dont want nothing. They really want something, because they dont want nothing.