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mudchemist

Chassis Dolly Fabrication

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I posted pictures of the chassis dolly I built for my Otto-Bot racecar project and received requests for measurements. I will put those details below. I am sure a few of you have some ideas and comments to make things easier, better, and most importantly, safer.

Disclaimer

I am not an engineer or a welder. To most of you I am a stranger. Think about that before you build a dolly using any of this info and crawl under your car. A 2002 doesn't weigh much...until it lands on you.

I bought a caged chassis as pictured below. The owner would not part with the dolly so I had to return it and build my own. The basic design I used is similiar, but you will see some fabrication differences such as butt welded joints versus my overlapped box assembly. I like this dolly because the angled front supports make it easy to pickup the rear and tilt it onto a trailer. (Try using ramps with 5" swivel castors if you like getting hurt)

Old Dolly

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My finished dolly

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What you need:

5 8' Sticks of square tubing. I used 2" at 0.125" thickness. You will have a little left over.

8-10" of 1" round tubing. Big box store. (I think this is the weakest link...think about beefing this up.)

2-3' lengths of 3/16" thick by 2" wide flat bar. You need this for the front subframe mounts plus gussets. Big box store.

You can use your front/rear subframe bolts for attachement, or go to 3/4" x 5"+ bolts in the rear with washers.

Good drill bits for the 17 mm bolt holes in the flat bar.

Chop saw if you have one.

Mig or Tig welder. You could go gasless but you want to buy it....go ahead.

Grinder to clean up cuts.

4 5" Harbor freight swivel castors sku 38711.

Framing square - magnetic squaring tool

Band Aids.

Beer.

More band aids if you have beer.

Health insurance if you have beer and bandaids don't work.

Red metal flake paint with flame decals. Optional.

Donation to FAQ website for giving us a forum - highly recommended. I know you see that donation/paypal button. Stop pretending like you don't use the site often enough.

All measurements are +/- ~1/8". Remember that welding heats the metal and can distort the lengths if you get over ambitious. Mock up, tack weld, check again, then weld.

This is the drivers rear subframe mount showing the box overlap construction. The tubing running the width of the car is 49". The uprights are spaced 45" apart on the inside width. Wheels go on last. Drill and bolt or weld them.

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I started by cutting 17" uprights out of the 2" tubing. I then welded a small 3/16" flat bar spacer and then connected the 1" tubing. You need the spacer for clearance of the washer and nut. Like I said above, this is the weakest link I see in the system. Consider beefing it up. (This is the passenger side). I attached these uprights and made sure they lined up properly on the horizontal before welding. You don't get much wiggle room here. Mock-up and be sure before you weld.

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Now that you have the rear worked out cut another 49" horizontal for the front width, and 2 60" tubes for the length. You can lay these out and just weld them together using a framing square and cross-corner measurement to make sure its square.

You can fabricate the front subframe mounts using the 2" bar stock. Cut a piece the length of the bolting area and drill out mounting holes. Then weld on 2 3.5" pieces to either side so you can mount to the uprights. I chose to weld mine, but you could also run a horizontal bolt hole here to attach the angled upright.

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Now you need to work out the angle coming from the front support down to the dolly. I roughed it out with an angle gauge. Ended up cutting the angle uprights at 39" length. I clamped them in place and began welding. You will see that a basically allowed them to rest on the top and then welded scab plates using the 3/16" flat bar stock. If you do it this way, weld every seem. Probably add some gussets as well since this will put some twisting stress on the dollies front width bar.

This is the mount of the angled upright to the dolly frame.

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Add your wheels. Bolt or weld.

You will get about 22" of clearance from the rockers to the ground. High enough to crawl around, low enough to still bang your noggin on the rear differential tabs if you are not paying attention.

Paint it before the rain comes in....as you can see from the pics I was working late so I didn't get to it. Humidity colored up the weld areas in one night.

Okay...so you more experienced guys can now finish the thread...post a link to some obscure thread that covered all of this 5 years ago that only you can find because you have mastered the search engine, or go back to you endless search for the ever elusive 6 fuse cover in mint condition for $5.

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That looks good I'd love to have one for my 02 restoration would make life easier.

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I built a dolly out of 4x4s, just a square the width of my trailer ramps with casters. Screwed it together with wood bolts. Cheap, quick and easy to build, also very durable.

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This is just what Ive been looking for. Thanks so much for taking the time to spell it out for us amateur types. Do you think it could be modified with some outriggers to make a "tiptisserie"? I have limited space and height in my shop, so it's nice to have the ability to tip the car, even at a 45 degree angle.

 

Hmmm... gotta think about that.

 

I don't own a chop saw, unfortunately. Would it be utterly insane to attempt to cut that much steel with an angle grinder and a cut-off wheel?

 

Also, where did you source your bar stock? Seems like more than what the Home Despair would stock.

 

:D  Thanks!

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