Axle alignment question...

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Hi! My first time welding was last week, but actually produced a pretty strong steel frame. I'm designing and building a food cart and needed a steel frame to put my wooden box on (see pictures). I've come to a bit of a stand still for my next step and thought I'd see if anyone has a good suggestion for me. So here is the scenario:1. I've welded a small steel frame from 3/4" stock. I want the frame to also act as a drop axle, which is why I added two 8" arms on the sides (see orange circles). The box fits snugly between those arms and lays flat on the frame, for example the image with the red frame (green circle). And the tow arm attaches to the bike (red circle)2. I'm using a drop axle approach because the box must only be lifted 6" off the ground in order to have a 3' counter space on top and I want to use wheels larger than 12".The problem lies in the axle... I COULD have the axle go straight through the box to the other wheel, making alignment not an issue, and keeping a very simple design, but that rod going through the box would create a problem packing and unpacking gear to the rear of the box. So here is my plan (see paint diagram)Have a bolt go through the box's plywood, and through a 1/2" drilled hole on the drop arm, tighten down very snug with a nut, and then slide the bearings onto the bolt and snug tight with a lock nut. This solves my problem of having an axle go through the cart, and of having to weld an axle to the end of the arm. I am just wondering, in your opinion, would I be in danger of having the axles being extremely off alignment? Would I be in danger of having axles that eventually become very floppy and weak? The cart is expected to be around 300lb by the time I'm done. Any suggestions? I've had fun problem solving so far with this project but I'm at a standstill. Is welding the only way to go? Attached Images
Reply:Ideally you want the wheels to be perfectly parallel to each other and to the bicycle wheels. If they're only a little off it won't make much of a difference especially since I can't imagine you would be going more than 5-10MPH with that.Since you've only been welding for a week, and I mean no offense by this, you really shouldn't be welding axles, even if it's just for a bicycle. I think drilling the hole and using a bolt would result in a more aligned axle than welding anyway. You'll get a lot of pull when you weld. As long as the wheels are parallel to each other, they'll align themselves to the bike as you ride. It would have been better if you could have drilled the holes in a drill press before you welded the arms on as you may have some issues drilling a straight hole now.John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Bolting to the wood will probally end up failing over time with 300lb dead load that can multiply to 600 even 1000lbs if you accidentally drop off a curb or something I'd weld it with some good diagonal bra sing to just check your square after tacking it then after welding if within say 1/8inch overall square you're good to go
Reply:You show using 3/4" square bar as the support member for a 1/2" bolt by drilling a 1/2" hole through the 3/4" cross section of the bar.  3/4" minus 1/2" = 1/4", divided by 2 = 1/8".  After you bore a 1/2" dia hole through your bar, you will only have roughly 1/8" of steel thickness to support that 1/2" bolt "axle".  I have serious doubts about that little bit of material being able to withstand the rigors of travel with the load you plan on putting inside the cart.  Every bump, gravel, or crack you encounter in the path you choose will exaggerate the loading/bending moment of the axle far beyond any static values you may have "engineered" into the design.You would do well to fabricate the axle bolt mounting bracket portion of your design from a small plate with a 1" X 3/4" cross section instead of 3/4" X 3/4".  And you need to make the bracket just a tad taller than what you have now so that the drilled hole will have more than 1/8" material between the bolt hole and the top edge of the bracket.  And, you should not have the bolt head resting against the plywood of the box.  The box should have an access hole bored through it where the axle bolt will be located.  Having the plywood material carry the compressive load of tightening the bolt securely will last about 10 minutes before the wood begins to deform, which will then let the bolt become sloppy loose in the bored hole of the steel bracket.See my edit of your drawing.  My red arrow indicates point of concern. Attached ImagesLast edited by walkerweld; 05-06-2014 at 01:26 PM.
Reply:Ahhhhh... This is exactly the type of feedback I was hoping for. I sort of imagined that the bolt head on the wood would be an issue but the idea to cut an access hole in the wood sounds like the best solution to my problem. I realize now yhat i should have drilled the holes first... So I'll just make extra sure to get a good 90 degree hole. What a great forum! Doing the woodwork, sewing the canopy, and fabricating the canopy frame was easy compared to the metalwork. I cant wait to learn more.
Reply:You may also want to make the tongue like a gooseneck trailer where it comes up under the shel and attacjes to the seat post above the rear tire. It would only take a piece of pipe that the seat post would go through to make the hitch. Seems it would be much simpler to build and would center the tongue of the cart making it tow much nicer instead of having a side pull on the bike all the time.
Reply:If your wheels are out of alignment  a little heat and a twist with a wrench or a whack with a hammer will bend the drop portion of the axel  and one can realign it, as far as it goes one could most like do it cold, with a large or long handled wrench or pipe wrench,  IN days gone by, they had tools to bend the I beam of the front axels on truck to align the tires on them. I have bent and realigned axels on 21,000 pound goose neck trailers so the tires did not wear.
Reply:Originally Posted by BobYou may also want to make the tongue like a gooseneck trailer where it comes up under the shelf and attaches to the seat post above the rear tire.
Reply:Use a solid piece of steel for the axle through the steel frame, weld it up, then cut off the center section and add your wood box. Everything should be in alignment then. A bike trailer is a good starter project. The only issues you may have would be health dept issues regarding sanitation.