I’m in for 2021… Going to try to build something that has zero practicality on my railroad, and really wasn’t built in the time period… But My RR, My Rules…
For Mik 2021:
OK guys… pile on for all the technical flaws… But it will be a wooden car. And yes in 1915 it haden’t been invented yet… But the back shop crew on the NMNRR didn’t know that, and so they built it anyway.
Dave T.
That’s a good idea, I have a couple old beer cans might give that a go after I finish my challenge
I really like this idea, Dave. No reason your guys couldn’t re-write history and invent the Schnabel car first. Heck, all they had to do was search the internet for a picture (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Got some time today ( after dealing with the roto-router man) shows you how my day started, and them replacing the battery in the wife’s car, to figure out just how in the hell I’m going to pull this one off… Having just come up with the idea on Sunday morning.
Thankfully I have two trucks already made, and plenty enough pieces to build out the other two, otherwise I’d be so way over budget just on the trucks. Put the ol’brain to work, sketched out some stuff and then made an effort to draw it out to be usable.
Basically i’m going to build, to start with 2 shorty, narrow flat cars to put the trucks under, keeping the trucks as close together as possible.
I only found 2 ( of the 4 needed ) precast resin bolsters, and only one of the non-talgo truck journals, so it looks like there is some casting on my horizon too. And I have a ton of precut wood already, most of which will need to be cut down to size… Oh well…
The center part… I have a couple of ideas in my head, but haven’t worked them out yet… But I do want the car to be able to haul 30+ft loads, like another whole car, not just a pressure vessel, we’ll see…
Stand by…
Can’t wait Dave. Its funny to me that I had my idea before the guy who has had a year to put this together, lol. Shows you take no unfair advantage
Three weeks ago I told the wife…Here I know what the Challenge is to be… and I can’t think of anything special other then a tank car, or a water tank… Now I feel like all the other guys, and they only have a couple of days to decide…
Really, really, I didn’t have a clue until about 0448 on Sunday morning…
Spent some time working thru the drop deck portion of the car build. Called my Engineer friend and went over a design… concept… I designed what I thought would be a good structural design, he agreed…But he wanted to put in a ton of steel, I said no.
Here’s the engineering concept:
I may have cheated today… Oh NO!.. I cut up some scrap wood to the designed sizes so I could put together a proof of design mock up. BTW None of this wood or pieces will be part of the final.
This is how the joints will be joined. The diagonals will be on both sides of beams ( i only put on the one side for proof of fit…).
There will be 6 of these beams ( double ended ) across the deck.
Can’t wait to get started…
Dave T.
Not bad for a cheater! Will be very cool with all the angles and braces and bolts and rivets. Nifty!
I love the idea of a wooden drop-center car
Dave Taylor said:
I’m in for 2021… Going to try to build something that has zero practicality on my railroad, and really wasn’t built in the time period… But My RR, My Rules…
For Mik 2021:
OK guys… pile on for all the technical flaws… But it will be a wooden car. And yes in 1915 it haden’t been invented yet… But the back shop crew on the NMRR didn’t know that, and so they built it anyway.
Dave T.
Who is this guy Schnable? Shouldn’t it be a TAYLOR car? (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-foot-in-mouth.gif)
Who doesn’t like those heavy duty carriers? I’d say if your RR has a need for it then why not be the guys that invented it in 1915. I bashed up one of those years ago using Bachmann parts and I stretched the deck to 12" so it could handle a Porter loco. I like the extra bracing you have planned and using wood they would have needed it.
This will be a cool build to watch.
Dave I would like to offer the below optional construction technique. I have tried to address the loads and rotational forces on the various joints and make it a believable product. This is how I would (maybe will) build one.
Edited to correct oversight in Elevation and added Section B-B
Bob C, and et el… Let me preface this posting by saying, I am NOT an engineer, nor have I taken any classes in structural analyist. Nor have any advanced training whatsoever ever in structural design. Hell i’m just a photographer with very little college classes in anything other then the graphic arts field. That said…
I though that with Bob C’s. posting and such… I would let others in on my thinking as for the designs on my drop center heavy hauler. Please if I make a assumed statement that is incorrect, will someone smarter then me please correct me (encouraged with no hard feelings) and lets discuss the why’s and success…
Here is Bobs drawing of his proposed assembly layout. It is actually very similar to my original design. My markups are in red so we ( all of those that want to get into this ) can be talking about the same things. I know that some of my terminology may not be industry correct. So here goes.
First off: The LOAD FORCE is the weight of whatever the car will be carrying… assuming even weight distrubiation across the car. This applies a force that needs to be distributed outwords to the SUPPORT POINTS, which are actually resting upon another flat car. For this discussion we are assuming that this force is constant, equal to the LOAD FORCE plus the weight of the car structure.
To get the LOAD FORCE out to the SUPPORT POINT, the weight must be transmitted thru two joints ( labeled J1, J2 ).
When the LOAD FORCE is applied a vertical sheer force is first encountered at J2, meaning that the joint it trying to be separated (pulled apart) vertically. This same stress is also applied to J1. And then transferred to the SUPPORT POINT. In so doing the force is attempting to bend the J2 joint and decrease the angle and increase the STRESSES at Stress Point S1 therefore causing Brace B to go into a compression status. [ NOTE: Wood beams are strongest under compression as long as twisting and warping of the beam is controlled , and weakest when they are under tension (pulled) ] BRACE A is likewise under compression resisting Stress Point S2 to decrease the angle. STRESS at S3 is neutral being controlled by compressed BRACES A & B.
Now as the train starts to move: [ Note: the LOAD FORCES STAY constant not affected by the lateral forces] The LATERAL FORCES to pull the weight of the car plus the load on the car and the total tonnage of the loads being pulled by the train is applied thru the SUPPORT POINT, and transferred again thru joints J1, J2, and on thru the car body. This LATERAL PULL FORCE attempts to apply stress a S2, by decreasing the angle of J1, which is held in check by the compression of BRACE A. The stress is then applied at STRESS POINT S3 wanting to increass the angle at J1, this increase at J1 also increases the angle at S1, and then takes BRACE B out of compression and puts it into tension. This increases the separation forces at J1. As the forces attempt to straighten out the joints at J1 & J2 and trying to center the forces into a straight line between LOAD FORCE and SUPPORT POINT. All these LATERAL factors are reversed when the train inertia is applied from the rear tonnage when the train stops. Attempting to push the car together, or pull the car apart at J1 & J2 at each end.
Wood beams under tension are only as strong as the joints and mechanical connection holding onto the wood structure. Thickness (size) of the beam, type of wood species, location of the connector and type of connection all come into play as to the strength of the mechanical connection on a Tensioned beam.
To much heavy brainage for tonight. Tomorrow I’ll ( or someone else) get into the design differences and my reasoning between my design and Bob’s.
Dave
Close, working from the load out to the support …
The first force on joint J2 is not a shear force. Shear force is the force that tries to cut a bolt in half at the mating surfaces of two members being bolted together. The forces here are tension and moment. Tension is the force in the downward direction attempting to pull the joint apart vertically, being restrained by the hanger rods. Moment is the bending force incurred as the support holds up the upper portion of the vertical post trying to decrease the angle at S1, being restricted by Brace B taking the compressive load. Please note the mortise/tenon joint at the bottom of the post at J2 restricting it’s motion.
What does not show in Dave’s mark up is the added end beam, beam and tie rods holding the upper platform in place. The load is now transferred up the post through the hanger rods (in tension) to the upper platform which is keyed into the posts with mortise/tenon. The load will now be attempting to rotate the platform upward about the keyed joint. Brace A keyed into the post and platform beam limits this rotation being in compression.
Looking at this a second time (done it about 30 minutes last night just before posting), a few more updates I would make.
The horizontal beam in the corner of the vertical post and the sill beam, I would move that to the underside of the sill beam, or possibly some mortice and tenon joinery on the underside.
The horizontal beam at J1 I would move to the top of the platform, and probably key into the vertical post.
Add an end beam to the deck sills and change the angle on the truss rods through the end beam.
All bolts would have either tapered washers to match the joint or the beam would be mortised to match the angle and the washer would be flat on the bottom of the mortise.
Keep in mind that this is a Napkin Sketch, subject to revisions as final design dimensions are determined and incorporated. My intent was not to hijack Dave’s build, but present another thought on what ‘might have been done’.
I incorporated truss rods into my design to accommodate the 30+ foot loads Dave mentions in posta above. Also, for the span bolster for the trucks on each end of the main car, consider using two short skeleton log car types.
This actually a part of another NG heavy flat car I am working on, but thought it would serve well for your build as well.
I know Dave mentioned he didn’t want to use steel, but could you not use steel gusset plates at J1 and J2 (shown below) as another option? This is for my own interest, not trying to get Dave to change his design (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)
I was not trying to get Dave to change his design, only offering an optional approach. Dave will do what Dave will do.
The short answer is yes. The long answer is the bolting through the timbers when the forces tend to be rotational on the joint will generate forces to split the bolts out of the timbers. Bolting perpendicular to the grain is always preferential to bolting parallel to the grain. In this assembly all the bolts would be parallel with the grain. Using steel, angles in the corners (on both sides of the joint) would be better.
Thanks, Bob. It was not my intent to infer you were trying to get him to change his design. Sorry if it came across that way.
OH OH… Hey Bob, I just noticed that you edited your original drawing and added several structural things that weren’t on the original drawing that I grabbed and used.
One of the things that I left out of my drawing were the horizontal tie rods, cause I knew where they were going, and was more concerned with the layout and fit of the physical pieces. Also not shown were the bolt structure and placement… I did have the end beam and the board on the other end to bolt up to…
I never even thought of using the “HANGER RODS” between J1 & J2 to tie it all together. I also didn’t call out the blocking between the beams and the rods and bolts tying it all together, again I knew where I was going to put them and they didn’t come into play with the fit up.
And being the dummy at the time I never thought that I would be analyzing the physics either. Oh well…
24 hrs to GO TIME…
Dave T.
@Dan - I wasn’t directly taken in that light, but clarification never hurts.
@Dave - Any good design evolves over time with more eyes and ideas looking at it. And as you read in my last post, even the revised design could be revised again as more analysis occurs. I will be watching you build to see how the finished product evolves over the course of the build.
Ok gang… Heres my Final ( but may yet be revised ) construction design for the drop center part of the car. If i’m major wrong on any of these points, please point them out to me before I start to build.
And here is my thoughts and design principals…As it ends up its basically a composite of both Bobs and Dans thoughts, Braces and Gussets.
Referring to the same Joints, Braces and locations, and Stress locations we did on Bobs drawing. My BRACE B is working as a partial Gusset along with the physical gusset at J1 & J2 and Tied into BRACE A. The location of BRACE B in close proximity to the apex of J1 & J2 keeps the length short to prevent twisting, and actually transfers a substantial load force to the support Point, and taking partial strain off of the joints. It also works like a gusset in this transfer of LOAD and keeps the joint tied together during both Compression and Tension force transfer. Also spanning J1 it works to limit the stress load at S3 durning Lateral strain.
Brace B is a longer brace and in all loading factors is in a compression mode. Being that it is thinner than the beams its supporting, there is a real danger of losing its integrity by twisting or lateral flexing. Tying BRACE A & B together with gusseting, stabilizes any flex, and also tying all the BRACE A’s together horizontally prevents the bowing while under severe compression loading. All abutted beams would be assembled with Mortised and Tendon joints.
I also show locations where there will be horizontal bolting thru the beams and spacer blocks in-between the beams drawing all 6 beam assembles together. The thru running truss rods will be run in-between the beams and not protrude below the bottom, there by keeping the bottom of the car as close as possible to the rail head giving the maximum load height capacity.
The other design thoughts were in trying to keep the use of steel components to a minimum, so the car just very well of been built in the back shops of a small regional RR. with lots of local sourced wood, and limited timber wood skills. Lots of cheap bolts and nuts.
Dave T.
