2017 August 10     Metal & Shop  


Introduction


In the first article we looked at why a $150 lawn cart is light-duty, at best. 

If you want to haul more than about 200 pounds, you'll need a more substantial cart.  A mere five cubic feet of gravel-- half a cart-full-- and that's 500 pounds right there.

The foundation for any good cart is the axle, wheels, and tires.  In this article we'll concentrate on these.



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In This Article

Towing Capacity of Your Tractor

The Axle

Wheels and Tires

Measuring The Distance

Axle Tube

Axle Braces

Conclusion




Towing Capacity of Your Tractor


Just a quick reminder:  make sure the transmission can handle it.  Some modern lawn tractors can't tow much of anything without the transmission-- or something else-- going bad.  Disclaimer, and all that.




The Axle


We'll use a straight-through axle and no leaf springs.  This is normal for lawn carts. 

I would recommend an axle that's 3/4" to 1" diameter.  Anything less will bend too easily when weighed down.



I decided to go with the 1" diameter axle.  (Get yours through this link or this one and it helps support my site.) 




Wheels and Tires


Many lawn, garden, and ATV wheels are the bolt-on type.  For a cart, that adds some extra complexity and cost.  You need axle hubs that have their own wheel bearings, etc.  It can get really confusing, actually, if you've never built with these.

I wanted to use wheels that could go right onto a straight axle, maybe held in place by cotter pins.  That means the wheel must have self-contained bearings. 

This category includes some really cheap stuff that's often pre-fitted with the worst grades of pneumatic tires.  Even if you install inner tubes, cheap tires will eventually fall apart completely.  They are more hassle than they're worth.  I did not think cheap cart tires were really that bad, until I used them...



Cheap wheel rims tend to waffle easily.  This one I had to carefully hammer back into round.  And then the tires ended up falling to pieces anyway. 

Best bet?  Try a good pair of flat-free tires.  For a 1" axle, consider two of these.  They are rated for 500 pounds each;  that means you should be able to haul up to 1,000 pounds in the cart.  Not that you'd do that often with a lawn cart, but gravel is actually quite heavy;  10 cubic feet, and there's your 1,000 pounds.



Before you tow the cart around, don't forget to pack the bearings full of grease.  But don't grease them now, because it will just get in the way of measuring everything and designing the cart. 

Also, the wheels do have grease fittings (which you can't see in the picture because it's on the other side of the wheel).  Make sure you have a working grease gun so you can re-grease the bearings every month or so.  You might be surprised how fast wheel bearings wear out if they don't have enough grease. 




Measuring the Distance


Find a flat, level space outside or in your workshop.  Put the wheels on the axle.  Use whatever cotter pins you're going to use to hold the wheels on.  If you're going to use spacer washers, put those on there, as well. 



Now, measure between the tires.  Inside-to-inside measurement.  Then, subtract for at least one inch of lateral clearance per tire.  Preferably a bit more.  This is the clearance for the axle mounts that connect to the rest of the cart.

Example:  I measured 28" between the tires.  If you want a full 2" of lateral clearance for each tire, then subtract 4" from the total.  So in that example, you would get 24".  This is how far, outside-to-outside, the axle braces would be apart.

Also measure carefully the inside distance from spacer washer to spacer washer.  This will be the length needed for the axle tube, which goes around the outside of the axle so you can weld to that.




Axle Tube


If you weld directly to the axle, it will be difficult to replace if something goes wrong.  Besides, some axles are alloy steel which is difficult to weld properly.  It seems better to have the axle inside a sleeve, such as a piece of pipe.  Inside diameter should be just over 1", so that a one-inch axle can move easily.



This here is just a piece of scrap pipe.  It's rusty but it should work OK.  The axle doesn't really have to turn inside this;  the wheels have their own bearings.  Then again, you might want to grease the whole axle so it doesn't rust permanently into the pipe.  I would consider adding grease fittings for ease of maintenance. 

If you cut it to just the right length, there won't be side-to-side movement of the axle;  the wheels would act as stops.  I'm wondering if it might help to drill and tap the outer tube for set screws, maybe 3/8" or 5/16" NC. 

Don't forget to remove the heavy rust before welding the tube to the axle braces.




Axle Braces


These join the axle tube to the underside of the cart.  They will be made of square tubing, which we'll talk about in the next article.

Outside-to-outside spacing is 24 inches maximum, which will give these particular wheels 2" of lateral clearance when they're on the 40-inch axle.  In other words, you'll want the wheels to be able to turn freely when you tow the cart around with heavy stuff in it.  Probably a 1" axle will not bow that much, so you don't need a huge amount of clearance.  But I would go with 2" just in case.

If you ever install narrower wheels, you can always use more spacer washers.  Or you could make spacer collars out of steel tubing. 

For now, at least we've measured the spacing between the wheels, and the required clearances.  A key point of this whole thing is that a 40-inch axle doesn't have enough room to put the cart between the wheels.  We had to figure out where to put some axle supports, so we can design the cart to sit up above the axle... while allowing the wheels to turn.




Conclusion


This was Part Two in a series on building a lawn & garden cart.  In this article we considered the axle, wheels, and axle mount sub-assembly.

At this point we know the spacing for the axle mounts, which is pretty much the foundation for the rest of the steel frame.  This measurement is the one you really need before you can design the rest of the cart. 

In the third article we'll look at the materials and cut list for the basic framework.  Either there, or in a fourth article, we'll also do the welding.  And somewhere in there, I'll go over how to build the hitch assembly and the sides.


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Thanks for reading!





         


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