Suspension problems

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michaellynn2
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Re: Suspension problems

Post by michaellynn2 » Thu May 16, 2019 12:13 pm

I need suggestions. I read all these tips on what the weight distribution should be but I see no solutions. Does anyone have a LE Atlantic or Pacific that ran into these problems and found a solution? I found that when I softened the springs on the lead truck the locomotive sagged forward, This made the cylinders sag closer to the lead truck wheels and the head covers scrape the wheels edge. The only solution I came up with was to lengthen the driver spring hangers so the locomotive rode about 3/16" higher above the leading and trailing truck. Anything less put the weight on the front truck and the trailing truck.
michael george

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FLtenwheeler
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Re: Suspension problems

Post by FLtenwheeler » Thu May 16, 2019 12:24 pm

Please show me a picture of the lead truck with it removed from the engine.

Tim
He who dies with the most unfinished projects: Should of put more time into their hobby.

michaellynn2
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Re: Suspension problems

Post by michaellynn2 » Thu May 16, 2019 2:51 pm

For those with a LE Atlantic or Pacific locomotive I found a good solution for me. It goes back to the fulcrum that Dan Watson spoke about. The problem was to get the weight reduced on the trailing truck and the leading truck. If you follow the LE plans to the letter, half of the weight is applied to the trucks. (At least for me) The solution I found was to raise the fulcrum which is the load on the drivers. If you adjust the spring rigging on the drivers you can raise the frame which puts more weight on the drivers ( the fulcrum). The forward most hangers need to be shortened. The most rear hangers to the trailing truck must be shortened. By shortening these areas, the frame is raised and the frame pivots on the drivers making them the fulcrum bearing more weight.
I learned that changing the front truck, I did not stop the load from being applied to it. Machining the trucks bolster caused the locomotive the lean forward causing the cylinder heads to rub the lead truck wheels. This was not the solution. Shimming the truck put more weight on it. Only by shortening the forward driver spring hangers did I raise the front of the frame and putting more load on the drivers and decreasing the weight on the lead truck.
Only by shortening the rear drivers spring hanger, did I raise the rear of the frame reducing the cradle from bearing down on the rear trucks rockers. Before I made these changes, applying the brakes caused the drivers to skid on the rails. The pulling power of my Pacific has now increased considerably.

One note: This is what I did to solve the equalizing on my Pacific. I spoke of my lengthening my hangers in an earlier post and I made the problem worse when I did that. Sorry for any confusion.
michael george

jscarmozza
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Re: Suspension problems

Post by jscarmozza » Thu May 16, 2019 6:15 pm

The following are the observations I made experimenting with the adjustments available on my 1" LE Atlantic without making any modifications to the plan dimensioned parts.I moved the trailing truck walking beam pins to the front holes, it only shifted 10 lbs from the leading truck to the front driver, nothing changed on the trailing truck or rear driver, which was a surprise. I also tried replacing the rockers with springs, which almost fully compressed and didn't make any difference in the wheel loads, so I put the rockers back (random springs, it wasn't a legitimate experiment). I also observed that the boiler bears on the frame directly above the center of the lead truck and about 2" behind the trailing truck wheels directly above the rockers. This pretty much loads the trucks and not the drivers. I weighed a spare Atlantic boiler that I have and found that 55% of the boiler weight bears in the rear and 45% of the boiler weight bears in the front. As I understand the development of the Atlantic style engine the trailing truck was added to support a larger firebox, this and the location where the boiler bears on the frame has me pretty well convinced that Michael is correct, something needs to be done with the equalizing system to redistribute the load to the drivers, and the available adjustments aren't enough.

I think I know the answer to this question, how do you access the hangers that need to be redimensioned and replaced (I really don't want to remove the boiler). I received a PM with a really slick method for adjustable hangers, but again, at this stage of the game the only way I see to get to the hangers that need to be replaced is to remove the boiler, correct me if I'm wrong Michael.

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Fender
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Re: Suspension problems

Post by Fender » Thu May 16, 2019 6:39 pm

If the equalizing system is moving freely and not bottoming out anywhere, changing the springs is not going to have a noticable effect. You need to change the fulcrum positions to shift weight to the drivers from the trucks. This is first-semester engineering principles from analysis of static forces.
Dan Watson

michaellynn2
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Re: Suspension problems

Post by michaellynn2 » Thu May 16, 2019 8:15 pm

John, I have sent a Pm on what I did to correct the problem. Lets get off this forum.
michael george

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makinsmoke
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Re: Suspension problems

Post by makinsmoke » Fri May 17, 2019 7:26 am

I don’t read every post and subject, but do at times find some that talk in detail about things that many assume are common knowledge.

This is one of them.

I am enjoying it and learning a lot about suspensions, weight on drivers, and the effect of that in the engine tracking and pulling.

Please reconsider moving the discussion off post.

michaellynn2
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Re: Suspension problems

Post by michaellynn2 » Fri May 17, 2019 8:05 am

The subject were are trying to resolve is the suspension on the drivers of a Little Engines Atlantic or Pacific. If one follows the plans to a science there can be serious traction issues due to half of the locomotives weight resting on the trucks. My Pacific (4-6-2) had a great bit of weight on the trucks and it was extremely slippery. I fought the issue for many years and finally found the solution. The spring rigging on the drivers was such that very little weight was applied to them. In other words, the front of the frame was resting on the lead truck and the rear of the frame (cradle) was resting on the rear truck rockers. The middle of the frame was basically "suspended' over the drivers.

The answer was to raise the frame in the middle over the drivers and make a small amount of it rest on the front and rear trucks. To do this I shortened the length of the spring hangers on my LE Pacific to experimental lengths. As I raised the locomotives frame the weight on the drivers increased. BINGO!!! I kept going until the weight on the leading and trailing truck was acceptable. I now have a perfect fulcrum in the middle of my frame.

John on this post has a LE Atlantic and he has the same issues I had with my Pacific. His locomotive is a 1" Atlantic and has tighter spaces than I did with my 1.5" LE Pacific. That is the basics of what is happening on this post. John is going to keep us posted on his progress as he works on the spring rigging of his Atlantic.

As for my slippery LE Pacific, I have to try hard to get it to slip. I have over the years added some weight to it to increase the pulling power. The sand dome is solid and weighs about 12 pounds. The pilot beam is solid and not a cored casting. It added about 4 pounds to the locomotive.

Michael George
michael george

Berkman
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Re: Suspension problems

Post by Berkman » Fri May 17, 2019 12:23 pm

Could always wrap the boiler with lead sheet under the jacket or add a chunk of lead between the frame.

I'd imagine steel tires might make a small traction difference as well.

jscarmozza
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Re: Suspension problems

Post by jscarmozza » Sat May 18, 2019 7:35 am

I couldn't access the spring hangers to shorten them as per Michael's recommendation, with the LE assembly method I couldn't do it with the boiler in place. What I did was remove the trailing truck (again) and shorten the adjustable hangers between the rear driver leaf spring and trailing truck walking beam,this transferred a little more weight to the front driver. I then removed 3/32" from the heart rockers, (LE plans call for a OAL dimension at the rocker of 1-17/32", my dimension is now 1-7/16") this tilted the engine back slightly and balanced the weight on the drivers at 85 lbs each. For the first time I have space between the bottom of the journal and pillar binder, it's only 0.015", not the 1/16" that LE calls for, but at least now the engine is suspended. This space under the journal appears to be something that a lot of builders miss, I have two running Atlantics and two projects, and none of them have space under the journal. I now have 20 lbs on each leading truc axle, 90 lbs on each driver axle and 60 lbs on the trailing truck axle. The LE plan dimensions for the spring hangers appear to be too long to get the proper suspension on the drivers and with an engine built to the plan dimensions there is limited adjustment.

Here are a few things I discovered that I didn't expect: an Atlantic is front heavy, the boiler weight is 45%-55% front/rear and bears near either end, however, the chassis center of gravity (on my Atlantic) is about 5" back from the center pin of the lead truck. That looks to be about right when you look at all the weight massed in the cylinders, lead tucks, pilot, smoke box etc...
Also, check to make sure your leaf springs are properly seated, especially after bouncing the engine around transporting to and from your club track. A spring off its seat is what started this whole suspension thing with me. I trailer my engine and a few good bumps on the way to the club unseated a leaf spring and my slippery Atlantic wouldn't go at all.
Thanks for all the interest and helpful suggestions. John

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Bill Shields
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Re: Suspension problems

Post by Bill Shields » Mon May 20, 2019 8:59 pm

How about: make the lead and trailing wheels a bit smaller? :shock:
Too many things going on to bother listing them.

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Dick_Morris
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Re: Suspension problems

Post by Dick_Morris » Mon May 20, 2019 9:44 pm

It looks like you are making progress. To make front-to-rear weight distribution more equal could you add weight to the rear of the locomotive? On my RRSC CP-173 I added a lead filled air tank under the cab floor and may someday follow a suggestion to install lead filled engineer's and fireman's seats. I also have a chunk of 1" plate to replace the cab floor which has ribbed surfaces only about 3/16" to 1/4" thick.

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