freetors

I've decided to build a tire trailer for hauling all my junk to the events I attend. I'm tired of trying to cram everything into the car and then driving there on noisy, howling tires that wear out quickly. And now that 200twr tires are getting stickier and less street friendly I think this will be a wise investment. I'm still in the planning and parts acquiring stage. I know most start with a harbor freight kit but I would have to modify it so much that there wouldn't be much left. I have a unique set of challenges for mine as I need to take a lot of junk, most notably my long reach/low profile floor jack which weighs a ton and is really big, but it's the only thing that will fit under my car, and I don't want to take ramps. It will live underneath the deck. Also a smooth, non bouncy ride is a high priority because I don't want my stuff getting beaten up and the roads here are really bumpy. I have a set of fancy shocks for this trailer. Yes, that means independent suspension!

I have most of the major components I need. I still need a set of wheels/tires, Northern Tool apparently doesn't sell the ones I wanted at my local store. I also need materials like steel and such but I want to get my design more finalized first.

Here is a general overview of how things will be arranged. It's not that unusual.



Here are the shocks I got, some Fox mountain bike shocks. These things are super small and light, have 3" of travel, and come with 400 lb/in springs. They also have rebound damping adjustment and low speed compression adjustment too. These are actually a couple years old but brand new from ebay and aren't as expensive as you'd think. As of right now I'm planning on using a 4:1 motion ratio, that would be about 12" of travel which is obviously more than necessary but I'm hoping to get 4-6" of sag. This should give it a suspension frequency in the low 1 Hz range when loaded which should be cadillac smooth compared to the typical tire trailer. For some reference, my father has a harbor freight 40x48 trailer with a 100 gallon gas tank. Fully loaded it's about 950 pounds. With the standard 2-leaf slipper springs it has a suspension frequency of about 4 Hz. I ended up removing the second leaf and it was still something like 3.something Hz. It's no wonder these things bounce all over the place.



I've been playing around in solidworks for the past few days modeling up my trailer. I think it's mostly done except for the suspension linkage, I'm still trying to wrap my head around the needed geometries. Then I will try to optimize some things for strength/stiffness/weight. I will probably add or modify the deck support tubes depending on what materials are available or that I can afford for the deck.

I'm really happy with how the balance has turned out. With jack, tires, air tank, spare tire under the v neck, and empty boxes the tounge weight is right around 50 pounds. I'll be able to trim the final tongue weight by moving stuff between the front and rear box. Fully loaded weight should be about 600 pounds. I may also need to add a sway bar after it's all done.

robinson

You are over thinking this.

[attachment=97502::]

I've even stacked another set of tires/wheels on top.

I set the trailer tire pressure to about 30 psi and the trailer does not bounce around much.

King Tut

He surely has too much free time between AutoX events.

freetors

First, this forum is full of people who over-analyze everything from optimum alignment, tire pressures, brake pads, etc.

Second, I'm putting so much careful thought into this because I don't want a cheesy, half assed, flimsy trailer with little resale value. And doing it this way I can have exactly what I want and need.

Third, I'm doing it because I want to. I want the design/fab experience because I eventually want to build my own car, clean sheet. I also want to do it for the pride in building it.

E4RTH WORM JIM

Like it!

How long are you giving yourself to building it?

freetors

Thanks! I'm giving myself as long as it takes, but I think it should be done before the year is over.

boyguan

I would take off the rear end of the trailer. When exiting driveways it will scrape very bad. Maybe add some skid bars back there. If you can lower the CG of the wheels or the tote that would be great as well.

SportInjected

That looks very nice! Which trailer is this? also, what hitch are you using?

Thanks!

rrounds

I take it to save weight you'll make it out of aluminum? Looks like a very fun project. Please take lots of pictures and keep us informed of your progress.

ROD

rrounds

Oh, one more thing. I would run the floor jack left to right, not back to front. That way you keep the weight closer to the center line.

ROD