Plywood Storage Cart

[chopnhack]

I have this posted in another forum (still love this place!) but I didn't want to leave you guys out. I am continuing the eternal struggle of cleaning and one part of the problem is always building something new before the shop is clean :P

This time there's a good reason:

http://lumberjocks.com/chopnhack/blog/27902

[LCHIEN]

my comments:
put your long base of the wheel mount along the length of the frame instead of 90 degress to it. Gives you marginally more wheelbase and protection against tipping.
Also much better to have 2 fixed, two swivel (at one end) caster for stability... keeps you from pushing sideways which is more likely to tip it.

[chopnhack]

Very good point on the set of fixed casters Loring, thank you. Alas, the store only had 4" swivels and I didn't even think of that at the time - I figured the A frame would be inherently stable.

[pelligrini]

Looks like a neat design.

The t-track idea is interesting. I'm not exactly sure how it works though. If it works like I think it does, the board thickness will lessen the angle of any plywood you have leaning on top of it, it's probably not that big of a deal.

[greenacres2]

As i was looking at this, i realized that we have a skid that our log bed was shipped on. Measures approx 30" x 80" and was solid enough to hold 200 pounds of aspen log. Top and bottom slats are rough sawn 4/4. Sound like a reasonable base to build on?

I know i'd have to surface the top, and likely widen it--what would be a decent width?

Thanks for all your help, i'm learning a bunch but feel like i'll be a newbie for life!!

earl

[LCHIEN]

Very good point on the set of fixed casters Loring, thank you. Alas, the store only had 4" swivels and I didn't even think of that at the time - I figured the A frame would be inherently stable.

stability depends on center of gravity:
1. higher center of gravity = less stable, in this type of thing the COG is nearly 50% of the height (not good)
2. wider base where it touches the ground = more distance COG to support. Assuming the load is centered, the COG is the distance centerlinee to point of contact of wheel (less than half the width of the cart). In this case, guessing its around 12-15inches. Turning the wheelflange to get an extra inch buys 10% more stability. Having the wheels swivel moves the point of contact maybe another inch - pushing sideways reduces stability more,
3. Forces from the side (e.g. pushing the cart) forms a force vector with gravity. When this vector points farther from the center of the points of contact the stability reduces. The cart will topple when the Vector points outside the wheel base. Thats why you want to push fro the end, not from the side, the force vector got a much longer way before passing the wheel base to go when you push hard.

[chopnhack]

Thank you Loring for the detailed analysis. This reinforces why we need to consult with our engineers before we dream stuff up! If the unit becomes too unstable, I have a few options - I can disassemble the base and add weight to the platform (not highly desirable) or hinge it to the concrete block wall.

Since I am still dreaming things up, I saw an older Shop Notes that has a cutting station for plywood built as an add on to a similar A frame cart - If I go this route, I was thinking in light of the stability issue of maybe putting some blocks under the base when the station is in use such that it doesn't tip - the cutting station is not fixed and can pivot upwards by several degrees putting a large lateral load... let me show you a pic:

http://www.shopnotes.com/images/plan...ide/left-1.jpg