Engine Truck

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djlayland
Posts: 31
Joined: Thu Feb 01, 2007 6:41 pm
Location: Surrey, BC, Canada

Engine Truck

Post by djlayland »

Curious to know if anyone sees any engineering challenges with using a small heavy duty ball joint as the connection between locomotive frame and a 4-wheel engine truck. I was thinking it would allow the truck to freely move up and down, front and back, left side and right, through the ups and downs of the track. (While still using a spring/equalizer system for the axle boxes)

Is there any reason anyone can think of why this wouldn't work?
Anybody done this with success?
Thanks!
-David
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Steggy
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Re: Engine Truck

Post by Steggy »

djlayland wrote: Sat Apr 16, 2022 1:46 pm Curious to know if anyone sees any engineering challenges with using a small heavy duty ball joint as the connection between locomotive frame and a 4-wheel engine truck. I was thinking it would allow the truck to freely move up and down, front and back, left side and right, through the ups and downs of the track. (While still using a spring/equalizer system for the axle boxes)

Is there any reason anyone can think of why this wouldn't work?
Anybody done this with success?
Thanks!
-David

Been there, done that, although not with an actual ball joint—I used a self-aligning flange bearing. However you do it, you need to prevent roll, otherwise the loco will just tip over. In my trucks, I use small ball bearings in contact with wear pads on the frame to prevent roll, while still allowing the truck to pitch on uneven track.

I suspect you will find using an automotive-type ball joint less than ideal, primarily because of the need to provide an accurately-tapered hole in which to insert the stem. Also, you may find it difficult to separate the ball joint to remove the truck from the loco, due to the strong wedging effect of the taper. The overall length of the ball joint may be a problem, as well.
Last edited by Steggy on Sat Apr 16, 2022 8:23 pm, edited 1 time in total.
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Marty_Knox
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Re: Engine Truck

Post by Marty_Knox »

The four wheel engine truck is also called the lead truck. It is supposed to lead the rest of the locomotive through the curves. It is not just to take the weight at the front. The swing links or hear rockers provide resistance to lateral displacement.
djlayland
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Re: Engine Truck

Post by djlayland »

Had not considered one of these, thank you!
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rudd
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Re: Engine Truck

Post by rudd »

Look up "Bissell Truck" for an in depth explanation of the "leading" aspect of the lead truck and how it works. The lead truck should pivot R-L around a point quite behind it, which can be determined by mathematical formula.
djlayland
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Re: Engine Truck

Post by djlayland »

Thanks very much...will read up on it!
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ChuckHackett-844
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Re: Engine Truck

Post by ChuckHackett-844 »

In my experience an important factor in our scale is that the truck must have a lot of vertical travel and still be forced down against the track (i.e.: taking load) through the entire travel. In my Northern this is accomplished by the truck having a large diameter bolster pin with a large, long-travel, spring inside.

Our tracks many times have way over-scale vertical curves/dips, etc. and it's important to keep the truck in firm contact with the rail so it can do its job and not jump off at a slightly misaligned joint, switch point, etc.

The original builder of my engine, Dennis Riches (Kitsap, OR & Burnaby, BC, built 1960-1969) redesigned the lead truck four times before he was happy. My Northern is known for negotiating many tracks others cannot. Several years ago, Mike Venezia (then owner of Little Engines, NJ) asked if he could blueprint the truck. I loaned it to him under the condition that Dennis be given credit on the drawings. My understanding is that these drawings are still available from Little Engines.
Regards,

Chuck Hackett, UP Northern 844, Mich-Cal Shay #2
Owner, MiniRail Solutions, LLC, RR Signal Systems (http://www.MiniRailSolutions.com)
"By the work, One knows the workman"
Mountaineer
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Re: Engine Truck

Post by Mountaineer »

^^^ thanks for the history on your Northern. Thought it looked similar to a Northern I’d seen years ago in Vancouver!

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NP317
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Re: Engine Truck

Post by NP317 »

My new 90-ton Mikado requires that same front pony axle modification: to increase vertical motion while retaining lateral tracking.
I am close to getting back into my shop to begin this alteration/experiment.

Helpful to read Chuck's comments on this subject.
RussN
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rudd
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Re: Engine Truck

Post by rudd »

Those that are saying you need a large vertical travel - are those trucks just sprung, or are they equalized with the drivers? I am sprung and equalized with the front drivers on my mogul, which has not seen track yet. It's built just like Mr. Porter intended. Not much travel in the leaf springs. Plenty of up and down with the equalization.
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Bill Shields
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Re: Engine Truck

Post by Bill Shields »

Depends on the track..the rougher the track the more vertical you need.

Every loco I have built..including several from "proven" designs, have required tweaking to get them to run on every track I visit.

One track-> I had to completely remove the front truck for the weekend. The loco ran just fine on our local track but would not get around places at the track where I was visiting.

I have learned that running the empty chassis around without boiler is a good place to start...changes are a lot easier....

Folks at the club are (sort of) used to seeing me sit on the rear flat car, facing backwards holding a dog leash in my hand with a new chassis on the other end.
Too many things going on to bother listing them.
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NP317
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Re: Engine Truck

Post by NP317 »

The front pony truck on my Mikado is both sprung and equalized, per the prototype.
When I tested it on the terrible short loop of track around the Crisp Yard at Train Mountain, it had bad derailment problems.
When I ran it earlier at the Kitsap Live Steamers it had no problems.
Still, I want some more flexibility in that front truck, for safety.
To be done.
RussN
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