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..... & Today's Oddity Is .....
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 Posted: Fri Jul 26th, 2013 01:07 pm
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oztrainz
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Bernd wrote:
@ oztrains, I've seen the video and that's on of the two the has inspired me to "want" to build a diorama depicting these monsters un-loading a ship. Thanks for the thought that they may be 3'6" gauge. Could also be 3' gauge come to think of it.

Bernd


Hi Bernd,
from watching both videos, the gauge for the pusher tracks looks much wider than 2' gauge would when adjacent to standard gauge tracks.



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 Posted: Fri Jul 26th, 2013 02:53 pm
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mwiz64
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If the lash in a spur gear is set properly then you are right they have very little friction. Some people tend to tighten them together too much and the the friction is noticeable. Why do people thighten too much? They are trying to adjust out the "slop" in the system. There is always some slop in a spur gear system, at least there is in one where the gears are not very precisely cut and lubricated. That's where helical cut gears come in. By nature of their geometry they are less prone to slop but then they do produce more friction.

It's been my experience that nylon spur gears can be adjusted tightly with very little friction loss. That's because nylon is slippery itself.

So what creates a jerky motion in a model gear train? #1 A gear train with slop. #2 friction in the gear train. #3 A low quality motor..... #4 This one is model train related only.... Dirty track and pickups.

With all 4 present in many train models, is it any wonder so many trains operate in a jerky manor?

All of these are magnified in smaller models. The smaller the model, the larger the jerk appears to be and to make matters worse, the more precise everything has to be to eliminate it.

Last edited on Fri Jul 26th, 2013 02:54 pm by mwiz64



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 Posted: Fri Jul 26th, 2013 03:29 pm
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Herb Kephart
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One other thing that is sometimes noticed in model locos, is that going downgrade they are jerky, whereas going up the same grade they are smooth.

If a conventional worm and gear drive is involved, invariably this is caused by endplay in the worm shaft. Just the minimum of clearance is needed here--and some of the old open frame motors were sloppy in this regard. I've cured many with this problem by adding just enough of the right thickness washers to eliminate all but a little armature endplay.

And Mike is correct about folks setting spur gears too close to eliminate backlash. Nearly all gearing, except for clocks, uses a tooth profile called "involute", one of the features of which is that the gears will be free running with some more backlash than the calculated perfect dimension.

Herb



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 Posted: Fri Jul 26th, 2013 04:04 pm
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mwiz64
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Oh and I missed one other important cause for that initial jerk into action... I don't have the technical terms here but I think you'll get the picture.

Ever play with an electric motor by just spinning the shaft? Ever notice the coging effect? The motor turns in a jerky manor. This is called the coging effect. And depending on design, some motors cog harder than others. If you HAVE ever spun an electric motor by hand, you know what I'm talking about. What causes this? Well, it's the magnets in the motor and the teeth on the stator (core) interacting with each other. They try to rest in the position that leaves them in a state of equiliberium. If the motor is of high quality this position is exactly same for both poles on the core or the many teeth of the stator.

To try to under stand that, picture two magnets glued down closely together on a table and you with a thin strip of metal in your hand. Now try to put that piece of metal between the magnets such that it doesn't jump to one magnet or the other. That would be pretty hard, wouldn't it? But if you could place the metal exactly at the point where the attraction was the same in both directions you could prevent it from jumping to either side.
This is essentially what causes coging in an electric motor. The stator/core finds that perfect resting position and it takes an effort to be moved from it.

So with that long winded explanation comes the point. Every electric motor has a start up voltage. That's the power it requires to break that hold and move. Every electric motor also has an RPM/V constant. The minimum voltage needed to move the motor can be high enough to cause the motor to spin quite fast initially. This is that initial lurch into action that all electric motors have. Again, some designs are much better than others but there are tradeoffs to that.

How can we reduce the effect of that initial lurch into action? Deep gearing or a high gear ratio if you prefer that term. So that little 10 tooth pinion on the motor shaft spins that large spur gear at a slower RPM thereby masking that lurch into action. Worm gear transmissions, like many trains have, will need to have a fine pitch to them to smooth out this initial lurch into action. A motor that is precisely made and optimised to not have a high start-up speed will make a big difference too.

See, even us "simple" Civil Engineers remember some of the mechanical and electrical engineering we were taught back in school. The fact that I've been a "gearhead" of one type or another all my life has helped too.

Last edited on Sat Jul 27th, 2013 03:04 am by mwiz64



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 Posted: Wed Jul 31st, 2013 12:31 pm
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Bernd
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I must be really serious about wanting to build a Hulett un-loader diorama since I kept scouring the net for more info. I think I now have complete info to put together for believable model.

I've discovered more info on the poling locomotives with dimensions and that some of these facilities had their own power houses to power the facility. If your interested in how these electric locomotives came about, here's the link. Click on the Shunt engines for a pdf and also the The power House.

http://citizensvision.org/friends-hm/index.htm

If you don't have time to go there here's a couple of Snip-It's giving the pertinent info of the shunter locomotives.





So, mystery solved as to gauge and how they got power. I was right on both accounts of how hopper cars were spotted. They did use a form of cable to pull hoppers under the Hulett for loading and I did take a guess that this shunter engines could be electric powered. Now we know.

Bernd

NOTE: More pay dirt. There are two articles on constructing a Hulett. In the July 1998 Railmodel Journal, Lawson Stevenson. "Build A Hulett Ore Boat Un-loader"  wrote an article. Complete with drawings. The article can be found here.

http://www.trainlife.com/magazines/pages/346/25552/july-1998-page-42

A second article can be found here : "Building a Hulett Ore Unloader" by Garry Lance
Railroad Model Craftsman - Oct. 2007 Fortunatley I have that magazine, just need to dig it out of the stack I have.

Last edited on Wed Jul 31st, 2013 01:09 pm by Bernd

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 Posted: Wed Jul 31st, 2013 01:55 pm
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Herb Kephart
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You're really are serious about this, aren't you?

Hope that you have a   L   O   N   G   basement, or can rent a couple lanes at the local bowling alley---

Herb



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 Posted: Wed Jul 31st, 2013 02:30 pm
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Bernd
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Herb,

How serious am I, well I have blue prints in the mail from Bearco Marine Models of a Hulett loader and I've been looking at both Bearco Marine Models and Sylvan Models for a Laker to haul the ore.

My grand scheme of things is that I'd like to build a diorama and animate these un-loaders with a couple of David T's receivers to run the motors. In other words make the whole model R/C controlled and take it to the model swaps meets and shows to demonstrate R/C control. Show them what can be done not using DCC.

The next big question is will the enthusiasm stay high to accomplish this? Only time will tell.

Bernd

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 Posted: Wed Jul 31st, 2013 02:59 pm
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mwiz64
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Me, I just like industrial locomotives. I'd like to build a model of one of those. Ill have to calculate what scale one would be if I built it to HO gauge track or maybe On3 track and then see what I can manage.

Thanks for the extra info Bernd. I think your idea sounds wonderful, if you can pull it off and from what I've seen of your work here, I think you can.



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 Posted: Wed Jul 31st, 2013 05:06 pm
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pipopak
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I guess that modelling just one Hulett will need a barn-sized layout in HO. In On30 probably can be squeezed into a medium-sized hangar.... Jose.



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 Posted: Wed Jul 31st, 2013 07:01 pm
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Bernd
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Thanks for the compliment Mike. It'll be a long haul if I do. I think that shunter loco would look good in 1:35.

Jose,

Actually it won't be that big. An HO scale boat that carries ore, if built to prototype length would be about 6' long and 6" wide. Sylvan Models puts out a short one that is only 3' long. So if you want to do a decent model probably 10' to 12' in length would do. Then perhaps two sections on either side for the empty and loaded hoppers. This could be run in a circle to a storage yard. Still need to do a bit of research in this area. I've got over 32' feet of length in the basement.

Time to go do a bit more research.

Bernd

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