So here we are again, talking about roadbed bricks. Third time’s a charm? Well, not exactly…
While this go round is certainly an improvement over last time, there’s still more fine tuning that needs done. And while I’d love to say we’ve moved into the production phase and show how easily all the stringers for the ground level trackage were replaced, that’s not the case.
The wetter mix is definitely the way to go. And even though the release agent was used this time, the concrete still shrank and pulled away from the forms in the same jagged fashion. I’m thinking I’ll take the “draft” out of the 1×4 sides of the form and see if that helps.
Unfortunately, the new, taller dividers I 3D printed for this go round were too tall. Their height prohibited an end to end screeding sliding the shovel along the top of the form. But that’s easily remedied with a new round of prints for the next go round.
How Not To Screed
All things being equal, this time it took two glue sticks to prepare the form instead of one the first two times. I use hot melt glue to attach the 3D printed ballast profile molds to the bottom of the form as well as attach the dividers. It’s not a big deal that it uses two, but the inability to explain why it took two is bothersome.
The beauty of using hot melt glue is twofold. First, it’s not a permanent attachment and easily removed after a pour. Second, I can use the cordless glue gun to avoid tripping over cords. The battery still has plenty of power left after prepping the entire eight foot long form. Time to pour concrete!
Unfortunately while screeding this time around, I end up knocking one of those tall dividers loose, creating a goofy “wedge” slope between two of the bricks. I did this the first time around as well, trying to work the drier mix into the form. Again, not a big deal, as long as those two bricks are used together as a pair.
Taking A Different Approach
The main difference this time around is keeping the concrete wet. The hope is it will prevent the shrinkage and increase the strength of the bricks. I may have gotten a little overzealous while spraying down the excess concrete spilled on the driveway, by not missing the fresh concrete in the form by as much as I should have. Oh well.
I tried to wet the bricks every few hours, but even that wasn’t enough to keep the bricks from shrinking away from the form in the same jagged pattern as last time. Maybe next time keep the fresh pour out of the sun and a tarp? Regardless, the bricks remained in the form for a several days until I finally took the time to free them.
As much as I’d like to blame an uptick in work escalations, the truth is I got a bit lazy about it too. When I saw that same ragged edged shrinkage as last time, even using a mold release agent, it just didn’t seem as important anymore. Once the bricks were carted to the Barkyard, the 3D printed pieces were left strewn across the driveway, haphazardly stacked, for days.
That’s a mistake not to be repeated. The PLA plastic is not all that heat resistant, so it doesn’t take much to guess what happened to them, in June, in Florida, on a concrete driveway. That’s right, they melted. Well, they didn’t really melt, but they certainly became warped and misshapen from the Florida Summer heat.
In a moment of disgust with myself at leaving them stacked atop one another long enough to warp, I decided to lay them out flat on the drive, individually, to see if baking in the sun would flatten them out again. And it did! Talk about surprised. Once they were flat, I stacked them off to the side, where they would be shaded.
So a few more lessons learned on this batch. Don’t leave the freshly poured concrete or the 3D printed mold pieces out in the sun. Don’t have dividers that are too tall. Don’t wait to wash the concrete off the 3D printed pieces after breaking down the forms to release the bricks.
Prepping For Round Four
Along those lines, for next time I’m considering cutting that eight foot long form into two four foot long forms, hoping to be able to more easily move them after a fresh pour. The addition of a third four foot long form should help to avoid the waste when mixing up an 80# bag of concrete too.
I’ve already 3D printed a new, shorter set of dividers, and test fit them to be sure. I may need to 3D print more of the ballast profile molds as well. Several of them were printed with less UV resistant PLA than the others, and they turned yellow and brittle sitting out in the sun for days on end. Some others need glued back together.
The biggest change will be removing the “draft” angle formed between the 2×6 base and the 1×4 sides of the form. Hopefully this will help reduce the amount of shrinkage and eliminate that ragged gap, or at least minimize it.
Are We There Yet?
Not yet. I already bought a couple more 80# bags of high strength concrete mix. Hopefully the next post will show some real progress in roadbed brick laying. There’s much more to accomplish before that can happen, and even more work to be done to run trains again. Baby steps.
If you read the previous post about the casting mockups, you may remember the setback when the A/C split unit in the garage “flooding” the table saw, shelves, and the casting bench beneath it. It’s setbacks like that to take away any momentum I had to start the concrete patch castings for the station retaining wall and culverts.
I had just spent the last few weekends getting things squared away and put back in their place enough to start using the casting and trestle workbenches again. All that work was wasted when I had to move everything back out of the way to gain access to the A/C indoor unit!
Bet you can’t guess where everything was left sitting afterward. Disgusted and discouraged I turned my attention to better organization, both in the garage and in the office. Along those lines, I picked up a couple of 12″ x 8′ shelves to replace the waterlogged and now hopelessly swollen and warped cheapo depo laminated ones the garage.
For the office, I bought a 16″ x 6′ shelf to replace the functional but stupid looking 2×6 over the window. Is it really stupid if it works? Here it would depend on the definition of stupid. If we’re talking stupid looking, yeah, it still looks stupid. Not for long, but that’s another story…
Making Progress… Slowly
I’ve been moving a chunk of furniture grade plywood around the office, generally every time it’s in my way again. Time to remedy that. It’s roughly 24″ x 45″, so ripping it down the middle yields two 12″ x 45″ shelves. One of them is now “floating” above the monitors for the work cell, thanks to the leftover floating shelf brackets from the previous shelving upgrade post.
The other shelf is now above the doorway to the bedroom, in hopes of relocating all the ½” plywood remnants from my old HO layout at the other house. AS part of this latest organizational effort, I cataloged all the pieces and their sizes in a spreadsheet. I went full OCD and captured models of them in the SketchUp drawing of the office too!
But let’s get the Barkyard back in operation before even thinking about yet another layout to build and maintain! The plan is to relocate those plywood pieces, mainly various radii curve sections, from the top of the shelves they are prone to falling off of to an out of sight and out of mind perch on that new shelf.
Speaking of OCD, I took pictures of the trestle bent inventory when last organizing in the garage, and created an inventory spreadsheet with all their sizes as well. This complements the design drawings for the various trestle templates. There is much more detail in the Trestle From The Deck post.
Next Steps
Most everything that needs done has already been captured, but prepping for round four did not include any activities outside of casting more roadbed bricks. The casting mockups for the curved approach to the station retaining wall sections revealed the original design is too narrow to accommodate the new USA Trains heavyweight passenger cars.
Thankfully there’s space for all these 3D printed mockups with all the new shelving, but there’s still more work to do there before we can expand the concrete casting to include those detail castings as part of the forms. It won’t be long now though.
Stayed tuned. There’s plenty more to come!