Wendy suspension vs. 'normal' springing.

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10KPete
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Wendy suspension vs. 'normal' springing.

Post by 10KPete » Thu Sep 01, 2016 1:35 am

The MEG design for Wendy has rubber inserts for suspension where all the other locos seem to have leaf springs or, in a few cases, coil springs.

I can wrap my head around the regular metal springs and have a mental feel for that. But what about the rubber? Is the ride hard? What about sufficient travel for articulation? Maintenance issues?

Please educate me!

Thanks,
Pete
Just tryin'

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Benjamin Maggi
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Re: Wendy suspension vs. 'normal' springing.

Post by Benjamin Maggi » Thu Sep 01, 2016 7:54 am

Though I haven't gotten there yet in my Sweet William build, Jack Buckler's book on building the Sweet Pea (which is similar to Wendy) explains the rubber blocks. The rear axle also contains the Hackworth valve gear, and as I understand it (but cannot possibly explain it) the timing of the valve gear is dependent on a fixed distance between the top of the link and the axle. As the axle goes up and down along the track due to variations in height, the valve gear timing is constantly being changed. It isn't to render the engine lame, but it may have minor impacts. Adding spring rigging to the rear axle introduces another place where the axle adjust and thus throw off the valve gear.

The book recommended hard rubber for that axle to reduce the amount of play which would hopefully make the valve gear more consistent. If Wendy has Hackworth valve gear, that could be why. The Sweet William (7.25" gauge) calls for springs on both axles and the book for the 5" gauge Sweet Pea mentioned springing both axles as an option.
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NP317
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Re: Wendy suspension vs. 'normal' springing.

Post by NP317 » Thu Sep 01, 2016 9:37 am

There is a beautifully constructed Wendy steamer at the Kitsap Live Steamers that experienced the timing issues with the Hackworth valve gear and inherent motion between the frame and wheels. That loco now sports beautiful Walshearts valve gear, and runs square at all times.
I believe it uses springs, too.
Food for design thought.
~RN

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cbrew
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Re: Wendy suspension vs. 'normal' springing.

Post by cbrew » Thu Sep 01, 2016 9:48 am

imho, the rear axles needs to be ridge for hackworth (less) to stay in time at all times.
just need to spring the front axles and the cross walking beam will be handle also if track does not have class A grooming :)
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Re: Wendy suspension vs. 'normal' springing.

Post by Pontiacguy1 » Thu Sep 01, 2016 10:54 am

I've seen several locomotives of this type running with the Hackworth gear and using a rubber block above each rear axle. I've seen then on some very rough track, and they tracked very well. It seemed to bob about quite a bit, but it wasn't a problem in the way it ran, pulled, etc... You're not going to be riding on the locomotive, so what does it matter if it bobs around a bit more if it doesn't have derailment problems? Those I have seen were pretty decent performers for their size, and sounded just fine with the Hackworth gear.

Any 0-4-0 is going to bob around on rough track, so I didn't think it was excessive.

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Harlock
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Re: Wendy suspension vs. 'normal' springing.

Post by Harlock » Thu Sep 01, 2016 1:07 pm

There's a lot of misinformation out there when it comes to spring travel and hackworth, and also some novel solutions.

Hackworth valve gear can have a sprung rear axle, but the spring travel must be no more than 1/8" of travel.

I have found the rubber blocks to be inferior to heavy weight coil springs that are spec'd to no more than that amount of travel given the weight on each wheel. Mine has rubber blocks, and it is almost like having no suspension. It doesn't ever de-rail, but it does move quite a bit. Since it's an 0-4-0 configuration, it does not have the problems of unequalized suspension on 3 or more axled locomotives. However Compared to my friend John Heald's hackworth engines and 0-4-0s that all have coil springs, it can feel quite rough. Even though it has no problems staying on the track (even rough track) When I re-build the MEG chassis, in addition to the cast spoked drivers I have for it, it will also receive all new journal boxes that are modified take-up bearing housings with Danly coil springs. Here is a sample spring, used on the heavier Darjeeling B-Class locomotive 0-4-0: http://www.danly.com/cgi-bin/itemdisp.pl?item=18454

There is also a method to allow you to spring it as much as you want, and that is by making the slide mechanism ride up and down with the journal boxes. Normally the side blocks and the bar that attaches them sit in bearing tabs on top of the frame. Instead the tabs can be made as extensions of the journal boxes, protruding up from just inside the side frames. When the journal box moves, the tabs move up and down with it and the distance between the slide block and the wheels / return crank etc. remains constant. This is definitely not necessary if you do the springing right, but it's an option. There are examples of prototype engines that did it this way.

The other important item to note about hackworth is that the slide block pivot point must be located exactly vertically over the rear drivers. If you get that right, you won't have any problems at all.

Attached are a couple of pictures of John's latest engine, the Tamar. It uses Marshall valve gear but the motion is nearly identical, using a scissors mechanism instead of the slide block. (rotating wear instead of sliding wear, should last longer but it's harder to dial in)

In these photos you can see the adjustable coil springs on top of the journal boxes. The adjustment is made via a bolt the spring rests on that is threaded up into the frame. In this way the locomotive can be leveled precisely. Even weight distribution is also critical for having a smooth running 0-4-0 that does not porpoise with long overhangs.
IMG_2880_resize.JPG
IMG_2881_resize.JPG
To see an 0-4-0 with this springing in action, you can check out my video of John's B-Class with a GoPro rigidly mounted to the loco. This engine uses Walchaerts valve gear but the point is to illustrate the spring travel and balancing:



This engine has nearly 2ft overhangs on each end, and no porpoising or excessive bouncing, very smooth.

-M
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Harlock
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Re: Wendy suspension vs. 'normal' springing.

Post by Harlock » Thu Sep 01, 2016 1:46 pm

Pontiacguy1 wrote:I've seen several locomotives of this type running with the Hackworth gear and using a rubber block above each rear axle. I've seen then on some very rough track, and they tracked very well. It seemed to bob about quite a bit, but it wasn't a problem in the way it ran, pulled, etc... You're not going to be riding on the locomotive, so what does it matter if it bobs around a bit more if it doesn't have derailment problems? Those I have seen were pretty decent performers for their size, and sounded just fine with the Hackworth gear.

Any 0-4-0 is going to bob around on rough track, so I didn't think it was excessive.
That's my experience exactly with my MEG. It moves around a lot, but it stays put. Very heavy engine on only four wheels.

Huge amount of pulling power and sounds great.
San Lorezo Flume & Lumber Co. #2 - "Felton"
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10KPete
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Re: Wendy suspension vs. 'normal' springing.

Post by 10KPete » Thu Sep 01, 2016 1:57 pm

Excellent information, gentlemen!! It is exactly what I need to know before making any major decisions on this loco. There are a lot of design choices that I wasn't even aware of. For example the 'scissor' vs. slider.... still figuring that one out!! While the Hackworth is pretty simple, the Walsherts isn't really complicated and sure does look great.

I've never been one to blindly accept a design as given. I always seem to want to know how the design came to be and why, plus what options may be beneficial for changes.

Keep it coming!!

Thanks again,

Pete
Just tryin'

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Harlock
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Re: Wendy suspension vs. 'normal' springing.

Post by Harlock » Thu Sep 01, 2016 2:50 pm

10KPete wrote:Excellent information, gentlemen!! It is exactly what I need to know before making any major decisions on this loco. There are a lot of design choices that I wasn't even aware of. For example the 'scissor' vs. slider.... still figuring that one out!! While the Hackworth is pretty simple, the Walsherts isn't really complicated and sure does look great.

I've never been one to blindly accept a design as given. I always seem to want to know how the design came to be and why, plus what options may be beneficial for changes.

Keep it coming!!

Thanks again,

Pete
Slide = Hackworth valve gear
Scissor = Marshall valve gear

Marshall is a derivative of Hackworth.

They create basically the same motion, although there is a slight arc introduced into the marshall gear, the longer the scissors the less the arc motion.

Theoretically they should be about the same level of simplicity to time, but John said he had a lot more difficulty with the Marshall gear. It was a lot more sensitive to adjustment of the combination lever ratios. I am the one that talked him into trying Marshall on his latest engine, and I found that fact interesting. Robert Morris here on the board has also done Marshall and his engine is the one we studied as a basis.

If this is a first engine, I would stick with Hackworth if I were you. It works just fine and as long as you keep it oiled / greased the slide and die will not give you trouble. You can also convert later if you feel like it.

Here is an animation of Hackworth I found, captured from Charlie Dockstader's valve gear program. The critical item is the vertical placement of the left end of the green rod, where it connects to the combination lever above the wheel. That sets your travel. The centering of the valve is set up near the cylinder by adjusting the length of the valve rod. Not shown is how rotating the slide changes the cutoff and the timing for reverse or forward.



it's a very simple gear and it's easy to visualize and maintain, and it's all on the outside like walchaerts. Walchaerts' (and Stevenson's) advantage is that it is not as directly coupled to the reverse lever in the cab, as well as being able to achieve much lower cutoffs, something we don't need in scale. For full size engines this means that when the engineer goes to change the cutoff when the engine is moving, the engine won't tear the reverse lever out of the engineer's hand, and you can run very low cutoffs for fuel savings on mainline engines at high speed.

Just like more modern valve gears, Hackworth can be timed to run correctly in both full gear and in cutoff (notched back) I run mine probably around 65% or less cutoff at all times unless starting from a standstill on a grade. Saves a lot of steam. Hackworth can be timed down to about 50% cutoff with even valve travel.

-M
Last edited by Harlock on Thu Sep 01, 2016 3:04 pm, edited 2 times in total.
San Lorezo Flume & Lumber Co. #2 - "Felton"
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Pontiacguy1
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Re: Wendy suspension vs. 'normal' springing.

Post by Pontiacguy1 » Thu Sep 01, 2016 2:57 pm

Is this your first build? If so, I would definitely stick to a proven design that has been demonstrated to be successful, and not go changing a bunch of stuff, especially major components and systems. I would also err on the side of simplicity, favoring the simpler design over the more complex and time consuming one. I mean, do whatever you want to do, but whatever you can do to simplify the locomotive and shorten the build time will just help you to progress faster. Faster progress increases the likelihood that you will be successful in completing your project.
You can always build and run it as a Hackworth gear locomotive, and then change it to something else in the future if you are unhappy with it or just 'want to.'

Apparently, the above was posted as I was typing this in... so basically... What he said.

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10KPete
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Re: Wendy suspension vs. 'normal' springing.

Post by 10KPete » Thu Sep 01, 2016 3:14 pm

This will be my first locomotive, but not my first experience with steam. My biggest concern here, and I think most of you will indeed appreciate this, is I will be 70 soon and I want to run the wheels off this loco while I'm still alive!! That means the design in total and all its parts must be quick to build. I'm not going for a particular prototype, just a general impression of one of those really cute little Porters. I've always loved those. The loco must also be robust in all ways. I won't go cheap and sloppy. Too often in my life temporary stuff has become permanent and I hate that.

That's why it's so important to me to get it 'right' the first time (well, within reason!) and take no more than two years to build. It may sound nuts but I think with the right design elements I can do it. Not two years for all the tinsel, but for a basic operating loco. Tinsel I can add later. And I will have a bell, and a head light, and nice paint, and polished brass, and...... but I can add that stuff during runs!

I just wish I had started decades ago.........

But God willing and with the help of experts like you all I will do this.

Pete
Just tryin'

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Bill Shields
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Re: Wendy suspension vs. 'normal' springing.

Post by Bill Shields » Thu Sep 01, 2016 3:33 pm

a man after my own heart re: brass, paint, tinsel...and age (almost)

really heavy springs are the functional equivalent of no springing at all except as shock absorbers.

make the rear with heavy springs and assume they will do nothing except in the event of a really bad BANG.

pivot the front suspension.

this is how I saw my first Wendy 35 years ago and it ran just fine on some REALLY rough track...

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