# I need some help...



## DevinVaughn (Aug 26, 2015)

I have a tad of a lil' problem... I am planning to make a 3d model of a 4-4-0 or a 4-6-0, but there is one detail on what I'm missing, how the leading wheels are installed. I looked every pic I could, but each has the piston hiding where the leading wheels are connected to the Locomotive. I also looked at models, but the leading wheels aren't doing much to support the boiler in anyway... also how does the leading wheels go up and down when going up slopes? does It use any spring at all? I'm so confused    i thought of this diagram i made... but it might not be accurate. if anyone has any advice on how the leading wheels really connect, please tell me.


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## peter bunce (Dec 29, 2007)

Hi, 

The center unit (with the sloping lines) you show on your drawing is a pivot, with a spring outside it; that is the way Bachmann use of the 4 6 0 otherwise known as the 'Annie'.

Thus it can rotate, and lift at the front , with the back going down, on the same pivot as the track rises or fallls; the spring keeps it on the track.


Here are a couple of photos of the Bachmann truck -











Note also that there are pickups - the spring on these can be a bit weak - I add some lead, making sure that there are no shorts to the upper and lower faces to allow 'gravity' to assist it.

Yours Peter.


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## Ironton (Jan 2, 2008)

Devin,

Welcome to the forum.

I donot hink you want the diagonal brace in your drawing. Most locos will simply pass a bolt up through thte middle of the truck to the frame of the loco. The frame is usually tapped so the bolt screws into it. The truck hole is loose so the truck can swivel in both the horizontal and vertical directions. Then if you wish you can slide a spring around the bolt before you attach the truck to the loco.

Alternatively you can leave off the spring and simply weight the truck to keep it on track.

Somewhat common solutions to your problem. Hope this helps.


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## Pete Thornton (Jan 2, 2008)

> leading wheels aren't doing much to support the boiler in anyway


On most of our locos that is true - the spring on the Bachmann 4-6-0 is mostly to keep the lightweight truck on the track.

The spring isn't necessary either. If you have a slot on top of the truck to guide the truck side-to-side and allow it to pivot, then a spring is prototypical. But in many cases - especially when the truck is heavy enough and equalized to allow it to flex - all you need is a strap with a pivot at the front and the back, (more or less where you showed a 'brace'.) The rear pivot should be close to the front axle and the front on in the center of the truck.

This is the replacement 4-6-0 chassis that used to be supplied by Barry. You can clearly see the truck attachment strap. No springs.

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## David Leech (Dec 9, 2008)

Devin.,
Are you looking for information on the real prototype loco, or just some ideas for a model?
Regards,
David Leech, Delta, Canada


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## DevinVaughn (Aug 26, 2015)

Thanks for the help... but I was hoping for something from an actual locomotive, but the models that you did show me did give me some idea. this is helpful info and yeah... but still I want it to be as accurate to a real locomotive as possible.

wait... so the leading wheels don't really help keep the boiler up? I thought it was for both navigation and to keep the boiler from falling frontwards.


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## peter bunce (Dec 29, 2007)

Hi Devin,

A prototypical front bogie or single axle truck system is complicated, and has a both central pivots and side pads, those keep the bogie movement in control - full size railways do not have the sharp curves that model railways use - thus the sideways movement of our bogies, or single axle trucks are much greater, though still in an arc shape. There are also such aids as 'side control' springs to keep the front of the loco on the track.

In addition the full size locos have the castings for the cylinder valves etc., even on outside cylinder locos there is still the pipes and valves there leading to the smokebox and exhaust to the stack. That lot produces a lot of weight to which is added the smokebox and its interior, on a saddle all that is kept up by the bogie of single axle truck, not forgetting that part of the boiler weight will also be exerting a downward force. 

Generally our models do not have all that (though there is some of it in the live steam models naturally. 

The lead (weight) I mentioned is to stop the well known fault - the bogie truck is much to light (the spring is not strong enough to exert enough downforce), so the lead weight helps somewhat.

If you are thinking a model of a full size loco see if you can find a good general arrangement (G.A.) drawing showing the frame etc. The GA is shows most of the detail, though there are a whole large set for any loco as well - those detail the individual parts of the loco and tender if required. 

In the USA most locos were produced by private companies so it could be difficult, the larger railroads did their own so they could be a better choice to see what is involved in full size locos.

Here in England a lot of our railway companies built their own locomotives, and such drawings are easier to obtain from a very good number of railway publishers. 

Yours Peter.


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## Totalwrecker (Feb 26, 2009)

The lead / pony wheels were not to bear weight but to guide the loco through turns. 2 wheels for slower speeds and 4 wheels bogies for higher speeds. Trailing trucks did help support bigger fireboxes. The idea was to keep more weight on the front drivers.
Any weight on the pilot and pony trucks takes away from tractive effort.
Well that's my understanding...
John


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## David Leech (Dec 9, 2008)

Totalwrecker said:


> The lead / pony wheels were not to bear weight but to guide the loco through turns. 2 wheels for slower speeds and 4 wheels bogies for higher speeds. Trailing trucks did help support bigger fireboxes. The idea was to keep more weight on the front drivers.
> Any weight on the pilot and pony trucks takes away from tractive effort.
> Well that's my understanding...
> John


Sorry John, but I have to disagree.
The front and rear trucks of a locomotive carried a lot of the weight.
Sometimes as much as the driving wheels.
Maybe check a locomotive weight diagram and you will see this.
A front truck was also there to guide the locomotive into a curve and required side springs to do this.
The centre pivot point on the truck would slide side to side against the springs to do this.
All the best,
David Leech, Delta, Canada


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## David Leech (Dec 9, 2008)

DevinVaughn said:


> Thanks for the help... but I was hoping for something from an actual locomotive, but the models that you did show me did give me some idea. this is helpful info and yeah... but still I want it to be as accurate to a real locomotive as possible.
> 
> wait... so the leading wheels don't really help keep the boiler up? I thought it was for both navigation and to keep the boiler from falling frontwards.


Devin,
If you can be specific about the locomotive that you wish to build, I am sure that someone can find suitable drawing for you.
As I have just said, the front truck certainly does take the weight of the front of the locomotive.
Cheers,
David Leech, Delta, Canada


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## CliffyJ (Apr 29, 2009)

Hi Devon,

There are some historical works available on line that might help you in your model making. For example, a Locomotive dictionary (heavily illustrated):

https://books.google.com/books?id=j...page&q=locomotive builders dictionary&f=false

Google books is a great place to fish for stuff like this.

Best luck on your project, and please post the occasional pic of your model,
Cliff


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## chuck n (Jan 2, 2008)

Over the past few years I have been measuring the tractive effort of my engines. On average the tractive effort is about 1/3 the weight of the engine. 

Two of my newest engines are also my heaviest, USAT's GG1 and Hudson. The tractive effort of these is impressive in the number of cars they can pull, but the percentage of the weight of the engine, is among the lowest measured. 

The GG1 weights 34 pounds and has a tractive effort of 8 pounds (24%) and the Hudson weights 25 pounds and has a TE of 5 pounds (20%). The TE of USAT diesels is between 34 and 50%. The diesels have all their weight on the driving wheels. Both the GG1 and the Hudson have two axle leading and trailing trucks. It seems to me that a significant amount of the engine weight is distributed to the non-powered leading and trailing trucks, reducing the overall tractive effort, but giving better tracking and stability.

Chuck

I imagine that I could increase the tractive effort of these engines with softer springs, but so far I haven't put enough cars behind them to need more TE. I've pulled 8 USAT streamliners with the GG1 and today I pulled a string of 22 freight cars with the Hudson. Sorry, I was short of motive power and had to use a passenger engine in freight service.


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## rkapuaala (Jan 3, 2008)

Devin,
Leading and trailing wheels do provide support at the center post similar to coach wheels. But leading wheels were never meant to bear a large protion of the weight. On the 4-4-0 the boiler is primarily supported by the rear 4 wheels and the cantilevered frame. The weight on the leading wheels is minimal. They are there mainly to do as the name implys to lead the front of the engine around curves. That being they still picked up some of the weight and so were still sprung in many different ways, I've never seen a cross brace,,, but that's not to say it didn't exist because I have never seen every engine ever built.
What material are you printing in?


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## DevinVaughn (Aug 26, 2015)

Thanks for all the replys... and I did FINALLY find what I was looking for, an image of how the truck was placed on the engine. I found this locomotive pic, the engine here was an attempt to make the locomotives faster... it had to lift the wheel and piston ontop of an other wheel, but the attempt failed do to the wheels slipping or falling out of place... but what I found was the piston finnaly was moved out of the way, thus showing how the truck was installed, and matched your guy's details. thanks for the help guys, I found what I needed


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## David Leech (Dec 9, 2008)

rkapuaala said:


> Devin,
> Leading and trailing wheels do provide support at the center post similar to coach wheels. But leading wheels were never meant to bear a large protion of the weight.


I don't have a weight diagram for a 4-4-0 handy right now, but I am looking at the PRR E6s 4-4-2.
Weight on front truck = 55,200 lbs (23%)
Weight on Drivers = 136,000 lbs (56%)
Weight on trailing truck = 52,400 lbs (21%)
Well, I do think that 21% is a fairly large proportion of the total weight, and on this loco, together they carry 44% of the total weight.
On many railways around the world, there was a maximum weight that axles could carry on the tracks available so you can not put all the weight on just the drivers. Of course on locos without leading and trailing trucks, all the weight is indeed on the drivers, so the weight of the loco had to be managed.
Regards,
David Leech, Delta, Canada


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## chuck n (Jan 2, 2008)

I now know why the USAT Hudson has such poor tractive effort when compared to my other engines. I just measured the weight on the leading truck and the trailing truck.

The engine weighs 25 pounds. Here are the weight on the track of each of the trucks.

weight on track of front truck 2.72 pounds (11% of total weight)
weight on track of trailing truck 6.12 pounds (24.5% of total weight)

That means that only about 16.16 pounds of the engine weight is on the drivers. That brings it up to about 31% without the leading and trailing trucks. That is a value that is consistent for most of my engines.

To make the measurements, I used a kitchen scale with a piece of track on it. I measured the height from the table top to the top of the rail. I then put another piece of track on the table and built it up until it was level with the stop of the rail on the scale. I put the trucks on the scale track and the drivers on the table track.










I think that the springs used to push the trucks down on the track are a stiffer than those used on many other engines. Sometime I'll try this with the GG1.

Thanks David for giving me the idea.

I had no idea that much of the engine's weight was being supported by the leading and trailing trucks.

Chuck


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## rkapuaala (Jan 3, 2008)

David Leech said:


> I don't have a weight diagram for a 4-4-0 handy right now, but I am looking at the PRR E6s 4-4-2.
> Weight on front truck = 55,200 lbs (23%)
> Weight on Drivers = 136,000 lbs (56%)
> Weight on trailing truck = 52,400 lbs (21%)
> Well, I do think that 21% is a fairly large proportion of the total weight, and on this loco, together they carry 44% of the total weight.


For the 4-4-0 the rear drivers would bear 77% of the weight. In any case neither the trailing trucks or the leading trucks bear more weight than the drivers so my statement is mathmatically correct. The largest portion is born by the drivers because the leading and trailing trucks are separate intities carrying less weight than the drivers. Even addes up they still carry 56% which is greater than 44.


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## Totalwrecker (Feb 26, 2009)

David Leech said:


> Sorry John, but I have to disagree.
> The front and rear trucks of a locomotive carried a lot of the weight.
> Sometimes as much as the driving wheels.
> Maybe check a locomotive weight diagram and you will see this.
> ...



Thanks for the correction, no apology necessary.
John


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