# Switch spring force



## Brandon (Jul 6, 2011)

Has anyone measured the spring force that various brands/models of switches provide?

I know many switch springs are purposely weak so that if a train enters backwards through the switch it won't derail even light weight cars, but I'm not worried about that. 

What I'm looking for is the ideal pressure that will hold a switch where it should be to avoid it moving as trains pass over, yet is not overkill or too strong that it could break switch parts. I'm learning that finding the right bore of a cylinder is key to make sure you have enough force, but not too much so knowing what is a good range or optimal force is key, before I buy actuators. 

The various oz/lb forces that some Clippard actuators can achieve with dual action air pneumatics include: 5oz, 12oz, 30oz, 4lbs, and upward. For reference I'm using svrr switches which have abs throw arms in case max pressure is a concern on the arms (And svrr sells great pneumatics, but I'd like to avoid springs in the actuators (fewer parts, and no pressure held on points when I'm not running the layout, and equal force regardless if extended or retracted so calibration is easier)).


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## chuck n (Jan 2, 2008)

Brandon:

Unfortunately, there is no simple answer. It depends upon the weight of the cars, and who made the engines. Heavier cars, usually with metal wheels, will traverse a closed LGB or Aristo switch (with stock throws, either electric or manual. Cars with plastic wheels usually derail. LGB engines with pilot wheels (moguls and mallets) usually go through with out a problem. On my RRs the pilot truck on Aristo (Mikado and Mallet), Bachmann (Connie and K-27), and Accucraft (C-19, 27, and 28) derail passing through a closed switch. Bachmann Shay and Climax don't have any problems.

LGB must have a stiffer spring pushing down on the pilot truck than the springs used by other manufacturers.

There are probably some light 2 axle cars that might derail going through a closed switch without a spring or motor. I would think that the lowest rated throw would be best, but even then some cars might still derail.
Chuck


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## jimtyp (Jan 2, 2008)

Brandon, I think your the man for the job  

I use SVRR code 250 switches also, they are manually switched and I tend to put a lot of pressure on them. I think SVRR makes a really nice switch, but when running stock, primarily AMS, with scale wheels and scale flanges, I find they can pick points, or if the car is light and the flange hits the end of the point can hop/climb up (not sure if there is a more technical term  the end of the point and derail.
I run outdoors with track power and I find the more pressure the better the switch holds, and holds better over time and temperature changes. And the better the switch holds the more reliable the train runs. I had one derailment a couple of years ago and even though the same train had run through that same switch probably 200 times during that same day, something just finally moved just enough or a flange hit the switch exactly right to cause a derailment.

I think the amount of pressure may depend on things like running outdoors/indoors and if using track power (thus shorts are a concern for derailments). Outside and track power I'd recommend the maximum pressure. Indoors with a controlled environment, or battery operated where a derailment is not as big an issue as with track power, I think less pressure is more suited.

- Jim


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## SD90WLMT (Feb 16, 2010)

Sorry here..but I tend to think Jim, if your adding greater amounts of point pressure..to run reliably, that a closer look at the points is in order...

Look for a blunt end ..file a sloped angle to prevent flanges from hitting the point tip...

Look at where the points close to the stock rail..
They should sit in and blend well....
Unnecessary or extra pressure will just push the stock rails apart..and out of gauge...

Are your switches set with straight or curved track leading to the points?

I think the lightest amount of pressure is needed..if track work is in good order..

Dirk


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## Totalwrecker (Feb 26, 2009)

I make my own springs and remove the ugly control boxes attached to Aristo switches.
For my purpose I wanted flop over switches that light weight pilot trucks would throw.
I have a 2-8-0 C-16 by Aristo and a 4-4-0 by Hartland, both are er... were light, lead shot has been added, but no fiddling with the suspension. 
I use spring steel, bent to a V, between the rails. I use as light of tension as possible to hold the rails closed. I use batteries so continuity isn't a concern, If I was I'd use jumpers underneath.
Other than removing the boxes, I don't do anything to the 10'Diameter wide Radius switches. I do make sure the semi-enclosed throw bar area is cleaned out and all grit is brushed out of flange ways and between rail and points.

Both Chuck and Dirk have run on my tracks, the same day and I don't remember a derailment in the switches.... but I may have been distracted.... below is a link to my springs.

http://forums.mylargescale.com/16-t...ing-semi-automatic-manual-switch-machine.html

John


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## chuck n (Jan 2, 2008)

John, my mallet ran through your switches with out a problem.

I think the OP wants to remote control his switches.

Chuck


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## Totalwrecker (Feb 26, 2009)

Yes Chuck. Brandon wants dual pnuematics and wants to know the spring force required in oz. so he can replace it in air flow specs.
I was saying not much.
yer bud,
John


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## fyrekop (Sep 20, 2011)

John, As I recall the only problem Chuck's Mallet had was when it ran into that side board before you widened it


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## Brandon (Jul 6, 2011)

I'm eyeing the clippard ev/et-3m valves, some needle valves to control speed, and sdr-05 cylinders.

The pro of dual action is force is fully adjustable for both directions, unlike the 3ps-1/2 which has non adjustable 12oz of force one way, though it's fully adjustable the other once you overcome the 30oz of force needed to fully compress the spring.

The sdr-05-1/2 cylinders I'm considering are double action which would always require pressure to work but I'm fine with that. For 1lb of force it's 15psi and at 100psi it's 7lbs of force which is obviously more than enough. I like the idea that force is adjustable. They're also only 2.5" long with a 5/16 bore. One aspect I can't find an answer to is that they're a "rotating rod" which google and pneumatic sites don't say whether or not the rod _has_ to rotate to go in/out or if you have it attached to a non-rotating object, that it will then not rotate. (anyone know?)

Pros of single:
Less parts to fail.
Saves about the cost of a locomotive.
Force can be applied one direction if no air pressure.
Con:
Can't adjust pressure on switch for resting position at all, it's always 12oz.
Constant pressure could warp switch parts over years. (I just got some 3ps-1/2 cylinders in and it's apparent this could be an issue, I'm surprised how strong the spring is at resting position)

Pro's of double:
Can adjust pressure
Force for each position/direction is the same.
No constant pressure when railroad is not in use, so less potential warping of switch parts.
Con:
Costs more
More parts to fail
Won't hold switch if no air.

So the list does look in favor of single action, but I'm wondering about ignore that in order to get the same spring force.

To make the right choice, I really need to know what spring force people are using on their own switches and whether or not there have been any derailings at the switch with that pressure...


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## Brandon (Jul 6, 2011)

Well, I decided to do double action. there are several cons, I know, but unless one of us in the hobby experiments, we'll never know if it's better or not so I'll give it a shot. 

The final kicker was I bought a couple 3ps-1/2 and I was surprised how much force the spring return has, far more than I expected to be honest. And with the force it has it got me thinking that having a lb of force when the railroad is unused, through -20 degree winters and 110 degree summers (not to mention the rail hits 160+ degrees in direct sunlight) I thought over the years, the force might not be good on the switches. 

So without spring return I will have to have air running anytime I'm using the railroad, but I'm fine with that. When I went to harbor freight this last week to get a 5 gallon air tank, I saw a small airbrush compressor and thought, I have AC in the train shed where the pneumatic values will be, why fill and haul an air tank around if I can generate unlimited air right there. In my desk testing it works perfectly. Up to 58psi (that'd be about 4lb's of force on switches so waaay more than I need). But using dual action and also using needle flow control on each valve, I've slowed down travel of the cylinder to about 4 seconds for a 1/4" travel, very protocoltypical and fun to watch IMO.

Here's a look at my setup (not finished) 



Anyway, 15psi will give me about 1lb of force (the sdr-1/2" double action cylinders are 2.5" long and have 5/16" bore which is .07 inches squared of area, so 15 psi * .07 = 1.05lb of force. I can always drop pressure lower or higher and really be able to customize the force used to hold the switches which is ideal IMO. There are double the parts and more that can go wrong which will be interesting to see how well it works over the years.

Anyway, Greg or others, I'm curious what spring force you able to measure for your switches...


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## toddalin (Jan 4, 2008)

Brandon said:


> Has anyone measured the spring force that various brands/models of switches provide?


 
There is no spring tension on the LGB 1600 and AristoCraft 10 foot diameter turnouts. The points are free to flop from side to side and should be as free as possible. It is the turnout motor that provides the tension.


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## Greg Elmassian (Jan 3, 2008)

Ummm.... clearly that is what Brandon wanted... yes you are right technically Todd, that it is the turnout motor... but, since the 1600 came with an electric switch motor, and the aristo ones came with a manual one, I would surmise that ALL he wanted was the force, not an argument over minutia.

I have not measured mine Brandon, have had company since Friday, will try to get out this week.

Have to dig out a force scale. I know it is in the shop somewhere ;-)

Greg


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## John J (Dec 29, 2007)

Where did you get the electric valves. ?

JJ


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## Brandon (Jul 6, 2011)

John J said:


> Where did you get the electric valves. ?
> 
> JJ


Everything I'm using (minus locally bought 1/4" 250psi hose and clamps) is Clippard products, you can buy them directly from Clippards website or you can sometimes find parts (if you're looking for single parts to eval like I did for the 3ps-1/2 and a few sdr-1/2 cylinders, but I couldn't find them in the quantity I needed from recyclers) from ebay or other recycling sites -- use google shopping search to locate. 

The valves I bought are Clippard eto-3m-12 valves but any 3 way valve (ev-3m, evo-3m, etc) would work. X-Y-Z is Clippards model where Z is the voltage, Y is if it's 2-way or 3-way, and X is information about if the exhaust has threads, normally open/closed, and a few other formats. EV-3M-__ will likely be what most people want, but I wanted the option of threads on the exhaust port in case I decided to plumb the exhaust pressure from each to something else but I have no idea what but for a couple bucks more per valve it's worth not having to rebuy more valves.


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## SD90WLMT (Feb 16, 2010)

Well since you have those exhaust threads....
You might have the option of collecting all the exhaust ports together...plumbed into a chamber or muffler to control that new extra sound you'll be getting during cycles..

Or once they are all grouped into a single line ...route it away from the control panel...

Just thoughts....

Dirk


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## Totalwrecker (Feb 26, 2009)

route it to an animated balloon figure oh about 20 feet tall....
just silly


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## toddalin (Jan 4, 2008)

AristoCraft manual spring turnout mechanism ~95 grams

LGB 1201 turnout motor ~20 grams

As measured on a triple beam balance scale. Motor arm was "extended" and this is the force required to "push it in."


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