4xAggie 138 gal Pit Construction (4-17-16)

[4xAggie]

All-

First, let me apologize for not giving an update on my last work weekend back in August--I got some great pictures which you will see below.

I haven't had time lately to work on the project between the football season and studying for the professional engineering exam. I took the exam on Oct. 25th--I felt it went very favorably, but have to wait until mid/late December for the official word. The day before the exam, I did a "relaxation" day by smoking up a brisket and ribs on my little backyard cooker. Overall, I thought it was a great effort on the brisket--the ribs could've used a little more time.



I should get back to building in the next couple weekends. Here's what I did that last weekend back in August:

First, I cut out the opening for the air inlet to the firebox. After deliberating with my wife, I decided to go with a vertical slide/sawtooth type of system. That part of the build will be a future detail, but you can see the nearly complete firebox below.

I did a few other things to the box (like put a weld bead on the inside seams wherever I could reach and see), and prepped it for mating to the firebox. You'll see in the picture below that I beveled the top edge of the firebox for welding on another end cap and tacked on an angle guide to assist in attaching the firebox at the correct level.


I went ahead and marked up the pipe for the doors, and used a flat wind-up tape measure to get my elevations for the firebox relative to the pipe. I used some geometry/circumference measurements, which wound up working nicely (you'll see all of that stuff in other pictures).

I met my goal of attaching the firebox. I actually attached it upside down. I felt the weld between the pipe and firebox was critical, and I thought I could be safer and get a better weld quality by avoiding the overhead position.

I thought it worked really well, though I am afraid that I had trouble getting it level front to back (side to side is great). I think I drop off about 1/4" to 1/2" to the back of the firebox. I'm not happy about it, but it should help me drain the warmer box eventually.

Here's the setup:


I spent a lot of time trying to get a nice smooth weld/attachment on the front of the pit. It's probably not as nice now due to 3 months of rust.


And the money shot. I got to take my golden, Brody, with me to the ranch that weekend. He seemed to be pretty pleased with the work.



I've been trying to think about the trailer design and weight distribution a lot lately since it'll be another week or so before I can make it to the ranch to start working. I've worked up the weights and weight distributions, and now just have several options/questions about where to go on trailer size, width, and axle configuration (3,500 lb vs. larger, or 1 axle vs. 2). I may have some questions upcoming before I order the axle(s), but it may take me some time to get all of my thoughts down.
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Gig 'Em Ags!
4xAggie 138 gal Pit Construction

[k.a.m.]

4xAggie, your project is looking great as does the ribs and brisket. Nothing wrong with some down time it helps you get back on track some times. Keep up the great work I will be watching for more pics and updates.
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Always remember slow and steady wins the race.

Hybrid Cooker

[Alien BBQ]

Welcome, looks like you are off to a great start. I teach for A&M in their safety division (TEEX). Glad to see another right minded person aboard.
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[k.a.m.]

[TrailerBuilder]

4xAggie, not really sure where I have been on this build, but just read through it and got caught up. You have one fine build going on. Very nice work! Great idea to get the motor hoist to help move around the cooker. IMHO a motor hoist and a furniture dolly are two must haves for a build Keep the pics and the updates coming.
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X2 Finished Build
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Fire Pit

[Alien BBQ]

[4xAggie]

Thanks all.

Finally getting around to another update (on my birthday!). I also found out last week that I passed the PE exam, so I'm now a licensed engineer by the state of Texas. Not sure if that's a good or bad thing in relation to this project, but it will mean that I've got to be a little extra careful when it comes time to design/build my trailer.

Anyway, I made it up twice in November. The first weekend I put the other end cap on, and the second weekend I got the doors cut out. I'll post about the second weekend later.

Marking up the end cap:



Front of the cut, back of the cut, and the cut edge. Not so bad there, especially after not touching the torch since August.




It fit up nicely prior to prepping the edges for welding.


I cut and finished the hole for the warming chamber.



And, here you can see the weld set up with a full bevel and small separation.



After the first pass, and then the finished product.





The final step of that weekend was prepping the charcoal grill for cutting the doors. You can see the lines marked below.



One of the next things I've started obsessing over is planning out the trailer design. I'm planning to build this from scratch, so I have a lot of leeway with axle position, etc. I'm fairly conflicted in what I want to do, so I may try to lean on some advice. I've put together a really comprehensive spreadsheet for my trailer weights and distributions. Basically, I'd really like to figure out if I'm going 1 axle or 2, if a regular 3,500 lb axle is sufficient, and how big my trailer should be. A few general thoughts before I get into questions:

-From a size standpoint, I've always wanted to just go with 1 axle. This thing is already bigger than I had originally intended, and putting a second axle on means a bigger trailer, and more tires ($).
-That being said, I'm planning to haul this thing on 100 mile trips (Houston to College Station) a few times per year. If having the second axle is really going to help the ride, then that's something to consider.
-For sizing, I'm considering something between 10' to 12' long and 60" to 77" wide.
-I'm currently calculating a "fully loaded" weight to be around 3,100 pounds total. This includes about 500 lbs of load for "stuff" (wood, coolers, etc.), so my fixed trailer weight is coming is near 2,500 pounds. I'd put the axle as far back as I can to make the tongue/axle weight distribution correct.
-With the current layout, I'm anticipating the trailer to be loaded heavier on the right side compared to the left. With no extra load, the center of weight would be about 9 inches from the trailer centerline (7 inches fully loaded).


So, in general, my questions are as follows:
-What's the most total weight that you guys would normally want to put on a 3,500 axle? What about the total trailer weight under the axle (i.e. accounting for the difference in axle vs. tongue weight)?
-What about the 1 axle vs. 2?
-What size (length and width) trailer would you guys recommend for this pit (the cooker is 26" diameter, 5' long, and the charcoal grill is 22" diameter, 3' long)?
-Is there any concern about the trailer weight distribution being offset to one side?

If I can get my spreadsheet/graph converted to a picture and stored online, I'll get them set up so you guys can see. With it, you can see the trailer outline, the location/size/weights of the major components, the trailer center of mass, the tongue/axle weights, the weight distribution percentage in front of/behind the axle, and the angle between the center of mass and the trailer centerline (basically, how off-balance the trailer is left to right). I've certainly put a lot of thought into the design, done some research, and worked up a lot of analysis.
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Gig 'Em Ags!
4xAggie 138 gal Pit Construction

[Jim38344]

Personably, I'd definitely go with 2 axles, just for the better ride and smoother towing. You should be good to go then, with a lot of extra weight capacity. As for the weight distribution side to side, it probably won't make much difference one way or the other. I was always taught that in such a case, to have the left side be the heavy side due to the way most roads are crowned.

Very good looking rig so far. You do some excellent work.

For an aggie.............
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All's well that ends..........

[k.a.m.]

If my floor plan allowed it I would go with a 60" wide x 12' long single axle trailer and up the springs to 4000#.
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Always remember slow and steady wins the race.

Hybrid Cooker

[Wreckless]

While not intending to contradict k.a.m.'s advice, I have built a couple of trailers similar to k.a.m. suggestion but found myself wishing I had gone double axle just in the matter of safety in the case of a flat. On a highway road trip, when that weighted side tire goes down, I'm thinking you best be able to get her off the road muy pronto. I did run the heavier springs and pulled one leaf on the unweighted / unsprung side to balance the ride and level it out. It worked well but being the proper thing to do might be debated. I'm sure someone will chime in on that one.

[TrailerBuilder]

Aggie, your cooker build is looking fantastic. Very nice work.

On your trailer, just to be clear, is the 3100lbs your figuring include everything plus the actual trailer weight or is the 3100lbs the total weight rolling down the road? If the 3100lbs is everything, trailer, cooker, wood, and misc items, then a single 3500lb axle should be fine, but I would do as k.a.m. mentioned and go up to heavier springs. Most 3500lb axles have springs with a weight value of 1750lbs per side, (3500lb total) I would, and I always do, step up to 2400lb springs for my builds. You would be more than fine running a single axle this way. You'll have a consistent load on the trailer, meaning nothing is going to be moving around while driving or put in different locations. That makes it a pretty stress free life for the axle since everything is fixed in place. I would think a 5' x 10' or 12' would make a nice sized trailer for your needs. Best thing to do is draw out the different sizes and model them with your components and see which works best and fits your needs.

I see the point made by Wreckless about the flat tire and oh chit effect with that. Not too much extra effort to carry a spare along for the ride, and always recommended no matter how many axles you have

Wreckless wrote:

[Wreckless]

[4xAggie]

Thanks for all the responses.

Jim - I hear you. I know for pure hauling purposes that the second axle is preferable. But, in truth, I really want to keep this more simple. I can handle a little more difficult hauling for as few times as I'll actually be hauling. That being said, the rest of the distribution has got to make sense if I only go for 1 axle.

kam - Thanks for the advice. My axle provider had me looking at wider configurations, but keeping it closer to 5' or 5.5' would fit my desired floorplan a little more. I'm keeping that in mind.

Wreckless - Great points. Hopefully an instantaneous blowout won't happen with pre-trip inspection and careful driving. I've never really felt that on a single axle (but plenty of times on a dual axle).

Trailer Builder - Thanks so much for chiming in. The next few exhibits should explain that a little better.

As an engineer, I'm think in terms of "Dead" and "Live" loads.
Dead loads are loads that are fixed/non removable, whereas live loads can be varied and removed.
The dead loads would include the trailer weight and anything permanently fixed to the trailer (i.e. the main parts of the smoker, a charcoal grill, etc.)
The live loads include anything that can be removed (like your firewood, coolers, anything randomly strapped to the trailer, etc.).
Since you could drive around with an empty trailer, you have to consider both a "dead load" condition, and a fully loaded condition that adds the live loads.

I've managed to get my trailer weight distribution upload (see below). This would be the dead load condition and the dead + live load condition. This would be for a hypothetical 5' x 10' trailer. I've done similar representations for a 5.5' x 12' trailer, which changes a few things. My total trailer length needs to be under 17.5' to fit into my garage for storage.

The weights represented include:
Dead loads:
Trailer (assumed at 400 lbs--this will change once I finalize the frame materials and size) + tongue (100 lbs) + firebox (471 lbs) + Warmer (281 lbs) + Cooker (799 lbs) + Charcoal Grill (380 lbs.)
Live Loads:
Firewood (330 lbs) + General trailer loads (up to 200 lbs) + general tongue loads (up to 50 lbs)

Plugging all this into my formulas and load balances, the charts show the total weight modeled and it's center of weight, and the axle/tongue weights. This example shows the axle pretty much as far back as it can go.

Dead loads only:


Dead + Live Loads:


That spreadsheet/graph can be easily changed for whatever width/length/position configuration I may want. Once I have the size pretty well figured out, I'll lock down the exact axle position/distribution.

Hopefully this lets you guys see what the weights really are on the trailer. I'd really prefer to just use a single 3,500 lb axle, but want to make sure I wouldn't be overloading it.
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Gig 'Em Ags!
4xAggie 138 gal Pit Construction

[TrailerBuilder]

Whew, glad you cleared up that dead load/live load scenario, in all my years of building, I had never heard of that

By the numbers that you show, you should be just fine with a single axle on your build. I would step up to a heavier spring and I would also think about stepping up to a little bit larger tire for a higher load rating, but that is just me. I would also take into consideration that your live loads will probably come in a little heavier that you have figured, not that Im arguing your weight calculations, I just know you'll be like anyone else and toss a few extra items on there last minute and add to the weight
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X2 Finished Build
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Fire Pit

[4xAggie]

[4xAggie]

Ok, as promised, here's my last work weekend, which was over the end of Thanksgiving Break. The next work time will be for 4 days right after Christmas, and I can't wait to get up there for it.

This last weekend was somewhat disappointing because a breaker on the welder wouldn't hold. Supposedly, this problem has remedied itself since I left (perhaps the weather had caused a small/temporary short in the generator portion of the welder). But, we also went ahead and got a buzz box so I shouldn't have to worry about that again.

The main purpose of that weekend was to cut out the doors. I'd done a good amount of research, and generally had my plan of work scheduled.
I had already marked out the cuts at 12 o'clock and 1 inch below 3 o'clock, and had left 1" at the corners and middle of each door for cooling before making the final cut. The plan for the weekend was as follows:
1 - Drill holes (I think they were 5/32") at the start points for every cut for smoother starts.
2 - Make the cuts with the oxy/acetylene torch.
3 - Use a 4 1/2" cutoff wheel or 7" carbide blade in a skillsaw to pre-finish both the cooker and door edges.
4 - Weld tabs on the doors as a guide to check the door fit. Note: I couldn't do this one since the welder was broken.
5 - Take out the remaining 1" sections to finish the cuts.
6 - Do final finishing by welding (as needed -couldn't do), grinding, and finishing on the cookers.

Overall it went fairly well, but I didn't really get to check the door fit after the cut.

I didn't get a picture of the drilled holes, but they were very helpful. On the charcoal grill, the air inside the pipe was trapped/compressed. When I finished the first hole, I could hear the air escaping. That was pretty cool for my welds on the end caps.

Here's the start of cutting on the charcoal grill and the main cooker:


Cool picture of the sparks inside the cooker as I was cutting:


Here are some of the cuts, with the 1" tabs left:


This shows the same cut after using the 4 1/2" cutoff blade for pre-finishing the cut.


Using the saw for the prefinishing on another cut:


You can sort-of see the bow of the cut before cutting everything away. This door may prove difficult to get a good fit (we shall see).

After fully cutting the door and before removing it:



Removing the doors:



The pre-finished cuts:


After grinding and finishing:




Since I couldn't weld, I went ahead and marked up my warming box plates, cut out the opening for the closer plate, and prepped the metal surface for welding to the cooker.



The doors (and part of the warming box):


Pit with the door cutout:

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Gig 'Em Ags!
4xAggie 138 gal Pit Construction

[k.a.m.]

4xAggie, your project is coming along nicely. Your cuts are improving from the time you started very nice indeed. I like to drill starting points as well especially with .375 wall pipe it makes the plunge so much cleaner.
I prefer 4" 5.4# channel iron for my trailer frames.
I look forward to seeing some more pics and updates.
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Always remember slow and steady wins the race.

Hybrid Cooker

[TrailerBuilder]

Aggie, your progress is coming along nicely and looking good. Only thing I seen missing from the to do list is the beer breaks! I look forward to seeing what you get done over Xmas break.

Tubing all the way on the trailer frame I most generally use 2x4 11 gauge for most builds but I do step up to 3/16th or 1/4" for the tongue. If you go the 5x10 or 12 route, you could get by using 2x3 also.
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[4xAggie]

Thanks kam (and trailerbuilder)!

I knew that those early cuts weren't what I was capable of...you've gotta have the right tips. If I could do this daily, I'm sure they'd get even better.

[TrailerBuilder]

From previous replies I kind of figured we'd get the typical engineer response...it looks good on paper. You can calculate and figure it to death, you go with what works best for your own application. No need to debate that one
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Fire Pit