Large Scale Central

Bachmann large scale Mallet VIDEO, from the B'mann site

General Discussion
#21

Chuck Cole,

The issue arose when TOC was writing his review for GR on the K. Dave calculated the gear ratio and it didn’t make any sense. The more we talked about it the more it began to come clear that they had produced this beautiful gear box, but had forgotten to include the double thread worm and worm gear (this is an absolute necessity, to prevent surging on down grades). If the gear box had been designed with a 29:1 gear ratio and then changed to a double thread worm and worm gear, the gear ratio would be 14.5:1. This is what had to have happened, because a 14.5 to 1 gear ration makes no sense. Further, the 9000 series Pittman motor is properly spec’d, just like my 8000 series motors, it is a HORSE and has enough power to overcome the
mechanical disadvantage of the 14.5 to 1 gear ratio.

We have surmised that by not fessing up (old texas term), they avoid any responsibility to correct the situation. But it is good to see the Mallet functioning so well.

Barry - BBT

#22

Barry,

Thanks for the explination.

Chuck

#23

Chuck Cole, you are welcome.

Jon Radder, not to worry there other things we’ll be doing; and I have barely touched the million Big Hauler that were produced. But, I do appreciate your concern.

Barry - BBT

#24

Barry

An interesting analysis.

Perhaps there is a simple way to test your hypothesis by asking a few simple questions.

  1. What is the scale speed of the K27 as shipped with a double lead worm at 18 volts DC with its 1/14.5 gear ratio?

  2. What would be the scale speed of the K27 at 18 volts DC be if the double lead worm was replaced by a single lead worm with the same 1/14.5 gear box?

  3. What would be the scale speed of the K27 at 18 volts DC be with a double lead worm but the gear box was replaced by a 1/29 gear ratio?

  4. What was the max prototype speed of the K27 on the valley line south of Alamosa?

  5. What is the gear pitch of the production double lead worm and the pitch of a similar single worm gear?

  6. What would happen to the currect gear box if the double lead worm was simply replaced by a single lead worm?

I think you will find the answers to these questions of interest.

Stan

#25

How about this:
If you have a 29:1 single-lead gearbox, all made up real nice with all the shaft spacing, and someone asks for a double-lead?
Guess what?
You get 14.5:1 automatically.

You probably are just confused and don’t understand.

See, folks?

#26
Curmudgeon said:
How about this: If you have a 29:1 single-lead gearbox, all made up real nice with all the shaft spacing, and someone asks for a double-lead? Guess what? You get 14.5:1 automatically.

You probably are just confused and don’t understand.

See, folks?


Hey Dave, is taht what you call “mechanically disinclined”?

#27

That’s a good term, I guess, for mixed audiences.

I have other, far more descriptive terms for the subject at hand, although not suitable for print medium.

#28

Ok. I think I’m confused.

We have two gearboxes with the same motor, one having double the ratio of the other.

Someone is claiming there was no problem with the K-27 gearbox. The same someone is claiming there is no problem with the 2-6-6-2 gearbox, which using the same motor, has half of the output of the first one.

That same someone apparently thinks that both gearboxes will drive the locomotive at the same prototpyical speed when 18 volts DC is applied to the motor … something close to a scale representation of what a locmotive would be found doing near Alamosa, Colorado, which is apparently the standard for such things.

So, unconfuse me … which model was designed with the serious gearbox error? The double fast or the half fast?

Matthew (OV)

#29

Maybe I’m missing something but it seems to me there are only three possible answers regarding the speed of the K:

  1. Someone goofed and the model ended up being produced with the wrong gear ratio by mistake; or

  2. It was intentionally made with a less-than-optimal gear ratio; or

  3. This 14.5:1 gear ratio is really a good thing, its benefits are not obvious, and no one has bothered to explain those hidden benefits.

It also seems to me that someone with the “inside scoop” at Bachmann could provide an answer one way or the other, rather than posing more questions.

#30
Curmudgeon said:
That's a good term, I guess, for mixed audiences.

I have other, far more descriptive terms for the subject at hand, although not suitable for print medium.


That’s what happens when someone who is less confused on matters mechanical is given not the whole gearbox, but simply the shaft.

“Sic Transit Gloria Mundia.” Or, perhaps “Eventus Stultorum Magister”

M

#31

Obfuscation!

Try to divert attention!

“Pay no attention to the man behind the curtain!”

#32

If I read this right, Barry made a statement, and Stan made a reply.

Barry said:

The issue arose when TOC was writing his review for GR on the K. Dave calculated the gear ratio and it didn’t make any sense. The more we talked about it the more it began to come clear that they had produced this beautiful gear box, but had forgotten to include the double thread worm and worm gear (this is an absolute necessity, to prevent surging on down grades). If the gear box had been designed with a 29:1 gear ratio and then changed to a double thread worm and worm gear, the gear ratio would be 14.5:1. This is what had to have happened, because a 14.5 to 1 gear ration makes no sense. Further, the 9000 series Pittman motor is properly spec’d, just like my 8000 series motors, it is a HORSE and has enough power to overcome the
mechanical disadvantage of the 14.5 to 1 gear ratio.

We have surmised that by not fessing up (old texas term), they avoid any responsibility to correct the situation. But it is good to see the Mallet functioning so well.

Stan says:

Barry

An interesting analysis.

Perhaps there is a simple way to test your hypothesis by asking a few simple questions.

  1. What is the scale speed of the K27 as shipped with a double lead worm at 18 volts DC with its 1/14.5 gear ratio?
  2. What would be the scale speed of the K27 at 18 volts DC be if the double lead worm was replaced by a single lead worm with the same 1/14.5 gear box?
  3. What would be the scale speed of the K27 at 18 volts DC be with a double lead worm but the gear box was replaced by a 1/29 gear ratio?
  4. What was the max prototype speed of the K27 on the valley line south of Alamosa?
  5. What is the gear pitch of the production double lead worm and the pitch of a similar single worm gear?
  6. What would happen to the currect gear box if the double lead worm was simply replaced by a single lead worm?
    I think you will find the answers to these questions of interest.

Stan

So, here’s what I took from Barry’s post:
The original idea was a 1:29 ratio, and the change to a double lead lead to an unintentional gearing mistake where the result was half that.

Here’s what I take from Stan’s post:
He posts 6 questions to “test Barry’s hypothesis”, but they do not address what Barry said at all.

The 6 questions are asking mostly what speed difference is there between a single lead and a double lead worm of the SAME gearing?

This is not the point… it’s “what is the speed difference between a 1:29 gear ratio and a 1:14.5 gear ratio”? That’s what the hypothesis is, someone made a mistake.

(no one was ever foolish enough to REQUEST a single lead worm, in light of previous experiences).

The answer is, as far as I can tell, the 1:14.5 will run twice as fast and have half the torque, which seems to be the reality on the K.

Regards, Greg

#33

Stan,

Some interesting questions.

  1. What is the scale speed of the K27 as shipped with a double lead worm at 18 volts DC with its 1/14.5 gear ratio?

Answer: The K27 may track south with the sun or the moon and seek warmer climes in the winter, but it does not move at 43 beats per second.

  1. What would be the scale speed of the K27 at 18 volts DC be if the double lead worm was replaced by a single lead worm with the same 1/14.5 gear box?

Answer: In order to maintain scale speed velocity, the European worm needs to move faster than the African swallow.

  1. What would be the scale speed of the K27 at 18 volts DC be with a double lead worm but the gear box was replaced by a 1/29 gear ratio?

Answer: A five pound locomotive could not pull a one ton coconut.

  1. What was the max prototype speed of the K27 on the valley line south of Alamosa?

Answer: Is that an unladen K27?

  1. What is the gear pitch of the production double lead worm and the pitch of a similar single worm gear?

Answer: Could the swallows carry the coconuts?

  1. What would happen to the currect[sic] gear box if the double lead worm was simply replaced by a single lead worm?

Answer: Will you go and tell your master that Arthur from the Court of Camelot is here?

#34

No doubt a mistake was made as regards the gearbox ratio on the K (initially the 30:1 ratio was selected, which was a good choice and then a double-lead worm was chosen to prevent surging downhill). However, it seems that with the infestation of juveniles into largescale, new locomotives either have to win tractor pull contests or travel faster than slotcars.

I saw a video of a K travelling very slowly (and majestically) over a trestle. One comment response was “Why is it travelling so slowly?” My comment is if this person wants a racecar then stick to gas-powered R?C cars and leave trains to those who know something about them.

#35

Slot Trains, Tim.
Slot Trains.

#36

(http://2.bp.blogspot.com/_ksx9Mx-xS-A/SJ7Fg1GK_nI/AAAAAAAAAEM/tnf9YURW_pk/s320/Bridge+of+Death.jpg)

WHAT is the air speed velocity of an unladen Swallow???

#37

African or European?

#38

summer or winter feathers?
north or south of the equator?

#39

Stanley,

Your first four questions are not germane to the hobby. Top speed is not relevant to running trains, crawling ability is much more important.

Number five gear pitches, have to match.

Number six, your word “currect” is confusing, is it correct or current? Please note that the single thread worms are matched with single thread worm gears and double thread worms are matched with double thread worm gears. I buy my worm gears and spur gears from Stock Drive and they offer each for the worm you are using.
Also they offer the gears in different pressure angles; i.e., 14 1/2 degrees and 20 degrees.

I spent a good amount of money having my worms customized by a shop in Colorado. What they did for my worms solved a series of problems, they created two worms for me single thread and double thread.

If the gearbox in the K-27 is so good, why was it changed in the Mallet? Also the gear ratio has been announced as being 1:28. If you have been so right, doesn’t this prove you wrong?

Barry - BBT

#40

Ah, but Stanley is never wrong, Barry.
He’ll prove it to you with posts like his last one!