# Pulling people with Ruby(s) at the NSS.



## dwegmull (Jan 2, 2008)

Hi,
For all of you going to the Summer Steamup in Sacramento: on Friday, at 9AM, we will try to find out how many Rubys it takes to pull a full size human (me, most likely!). The attempt will take place on the back patio where my dual gauge track (gauge 1 + 4.75") will be setup. Since this is ground level, you might want to service your engine on a table, indoors...


The track will be available starting late morning on Thursday as well as Friday all day. Feel free to bring watever engine you want to (try to) ride behind!


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## kfrankl3 (Feb 27, 2008)

I vote it takes one, downhill, with a running start!


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## Semper Vaporo (Jan 2, 2008)

Get yerself a long stick (two by four) that you can use to press down on ONE Ruby from your seated position in the riding car and see what happens!


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## Shay Gear Head (Jan 3, 2008)

Dave Hottmann's Ruby will probably do it; as it weighs as much as a K-27.

And it has enlarged cylinders and flue to boot.


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## Pete Thornton (Jan 2, 2008)

I'll bet it only takes one - if you use the stick to stop it slipping. Steam engines, even our little ones, are incredibly powerful. 

Mathematically, with 7/16ths cylinders (which I think are the originals,) there is a piston area of 1.375" taking a "push" of about 40 lbs/sq in, so the force is about 55 lbs. That should be enough to get you moving.


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## HMeinhold (Jan 2, 2008)

Posted By Pete Thornton on 11 Jul 2009 03:44 PM 
I'll bet it only takes one - if you use the stick to stop it slipping. Steam engines, even our little ones, are incredibly powerful. 

Mathematically, with 7/16ths cylinders (which I think are the originals,) there is a piston area of 1.375" taking a "push" of about 40 lbs/sq in, so the force is about 55 lbs. That should be enough to get you moving. 
Pete,
I get a different number: With Area = Pi x r x r, the area of 1 cylinder is = 7/32" x 7/32" * pi = 0.15sq" . As roughly only one cylinder is active at a given time (one is at dead center when the other one develops full torque), the force is only 6lbs. It is actually less, as the driving rods are not at the circumference of the wheel . So including friction you can assume about 4lbs of traction. In the ride-on world the ratio between traction and load is assumed as 1:20, so 1 Ruby could pull about 80lbs max. 

Regards


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## JEFF RUNGE (Jan 2, 2008)

Henner , I agree with you piston area, then .15 x 40 psi = about 6 lbs of effort on the crank, then you take the distance from the center line of the axle to the crank pin vs the wheel radius. (I don,t have that information) and you will have the maximum possible tractive effort being produced. 
Just for fun I ran all the numbers on the Aster Mikado vs the Berkshire, I had to use a caliper to measure the axle CL to crank pin CL The final numbers were in inch pounds of torque. These number however are never realized because of the angle between the piston rod and the crank pin is optimal after the pressure in the cylinder has begun to drop, and I did not get into the dynamics of steam expansion.


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## Chris Scott (Jan 2, 2008)

I don't think even Dave's Ruby will pull a person. It was a Shay that pulled Dan Pantages (last year I think) and it didn't weight close to Dave's Ruby, but it did have pretty good traction.


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## dwegmull (Jan 2, 2008)

So far the "weakest" successful puller has been a double head of a Superior and a Mogul. Together they can start and pull me easily, Either one by itself can keep me in motion if I help it by pushing it for the start. I think we will need around 5 Rubys... We'll see! 

Question: how many of you reading this will be willing and able to participate in this little experiment?


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## rwjenkins (Jan 2, 2008)

Is Cliff going to bring the K-36 prototype? Should be interesting to see what that can do.


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## Pete Thornton (Jan 2, 2008)

I get a different number: With Area = Pi x r x r, the area of 1 cylinder is 

Henner, 

I was wrong (in too much of a hurry - plus I keep telling people I have a math degree, which means I *always* get them wrong.) I calculated pi x d, the circumference. 

But you are also wrong, I think, as the radius is 1/2 of 7/32nds, as 7/32 is the diameter not the radius? So I make it 0.34 * 40 psi = 13 lbs. Still quite a lot, and maybe enough if it can get traction.


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## redbeard (Jan 2, 2008)

"I'll bet it only takes one - if you use the stick to stop it slipping. Steam engines, even our little ones, are incredibly powerful. 

Mathematically, with 7/16ths cylinders (which I think are the originals,) there is a piston area of 1.375" taking a "push" of about 40 lbs/sq in, so the force is about 55 lbs. That should be enough to get you moving." 

Whoops ! Factory Ruby cylinders are 3/8 inch instead of 7/6 inch. 
Larry


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## Dwight Ennis (Jan 2, 2008)

3/16 * 3/16 * pi = 0.1104 in sq.


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## HMeinhold (Jan 2, 2008)

Posted By Dwight Ennis on 13 Jul 2009 01:31 PM 
3/16 * 3/16 * pi = 0.1104 in sq. Pete, Dwight,
That's why I used 7/16" / 2 = 7/32" radius in my calculation, assuming a diameter of 7/16". I know, 9/8 of all Americans have problems with fractions







. That's why I stay with my simple and reliable metric system... Or may be I am just not yet smart enough for this complicated math. BTW, Pete if you are sure you are always wrong, just negate your result








Regards


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## Dwight Ennis (Jan 2, 2008)

Your math was right Henner, but as Larry says, the Ruby only has 3/8 diameter pistons and cylinders (9.5mm to you).







Actually, because it's Accucraft, I suspect they are probably actually 10mm (1cm) which is closer to 25/64 than 3/8.


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## HMeinhold (Jan 2, 2008)

Posted By Dwight Ennis on 13 Jul 2009 06:49 PM 
Your math was right Henner, but as Larry says, the Ruby only has 3/8 diameter pistons and cylinders (9.5mm to you).







Actually, because it's Accucraft, I suspect they are probably actually 10mm (1cm) which is closer to 25/64 than 3/8. 
Dwight,
I just measured them: They are a tad below 3/8" (0.373" vs. 0375" for 3/8"). Obviously 3/8" was specified and they used a 9.5mm reamer.

Regards


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## Dwight Ennis (Jan 2, 2008)

Thanks Henner. I didn't realize 1/2mm steps were all that common.


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## rkapuaala (Jan 3, 2008)

Dave, 
Its hardly a test with you. The real test would be if any number of Rubies can pull me


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## Dan Pantages (Jan 2, 2008)

Two years ago when we had my shay pulling people we found that it could pull a 200 pound person but not a 250 person.


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## rkapuaala (Jan 3, 2008)

Dan, 
Sounds like it will have some issue with me


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## Spule 4 (Jan 2, 2008)

Just last night in "my private library" I was reading some interesting info from smaller scale live steam (well, 15" gauge) poineer Sir Arthur Heywood about this very subject, with Heywood stating the following: 

On the level a steam loco can tow x10 its weight. 

Increase the gradient, and things drop quickly, (1:50 = x4 to 1:12 = x1) 

Hmm, I think I need to hit the treadmill if I got into riding behind a Ruby.....


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## redbeard (Jan 2, 2008)

So....how many?


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## dwegmull (Jan 2, 2008)

Well, 
I never managed to motivate enough Ruby owner to do a real try... The closest we got was a single Ruby pulled the empty ridding car. We tried pulling a small child (about 3 years old): it almost but not quite made it! 

Maybe we'll have better luck next year.


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## flats (Jun 30, 2008)

I am planning to build me a car to see if my mallet will puld me around my layout. 
I am interest to know what trucks you used under your car and how many, I though of 
4 roller bearing trucks, but will plastic truck be strong enough with metal wheels. 

Thank You, 
Ken owner of K&K the road to nowhere


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## HMeinhold (Jan 2, 2008)

Ken,
if you want to go around curves, forget it. The resistance goes up considerably, due to the flanges rubbing and the wheels not having differentials.
Regards


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## dwegmull (Jan 2, 2008)

Posted By flats on 30 Jul 2009 10:57 AM 
I am planning to build me a car to see if my mallet will puld me around my layout. 
I am interest to know what trucks you used under your car and how many, I though of 
4 roller bearing trucks, but will plastic truck be strong enough with metal wheels. 

Thank You, 
Ken owner of K&K the road to nowhere 
Hi Ken,
Let me clarify one point: my ridding car is 4.75" gauge. I have a special track with four rails that I built specifically to allow gauge 1 locomotives to pull people (or at least try to ;-)). The wheels and axles are from One Inch Scale Railroad, the needle bearings (axles are hardened) are from Mcmaster-Carr and everything else is welded steel.


Are you saying that you want to build a gauge 1 ridding car? Well it has been done! Somewhere, on this site: http://www.ne.jp/asahi/beat/non/loco/loco0e.html is a picture of an electrically powered, gauge 1 ride on train.
By the way that site is amazing and you will find yourself looking through its numerous pages for hours...


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