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Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
01-31-2013, 06:23 PM
Post: #1
Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
Some people don't consider Harbor Freight trailer frames to be very sturdy, and certainly at the low end of the HF line that's true, but the Harbor Freight #94564 4x8 1720-lb. capacity frame kit can be used as an excellent budget-friendly starting point for a strong frame for a 4' x 4' or similar trailer with a little reconfiguration. It's got a 2000-lb. capacity axle with 5-on-4.5" bolt circle hubs, which matches that of the Jeep Wrangler YJ, Wrangler TJ, and Cherokee XJ, as well as a number of other Ford and Chrysler products, so it's can be a good choice if you plan to share a spare between your trailer and your tow vehicle.

The following drawing shows how the pieces of the HF 4x8 can be reconfigured to become a much stronger 4x4 trailer.

[Image: FramePlan1_zps3a48dfe1.jpg]

And here's one on the workbench in the process of being reconfigured as shown above.

[Image: FrameConfig1.jpg]


A few notes...

- The drawing shows how the two unused side members (d and e) get used as a center backbone. Because they're being pieced together in the middle, unused crossmembers a and b slip inside them and are secured with bolts through holes that will be drilled through both the outer d and e members and the inner a and b members.

- In the photos of the 4x4 trailer in this post you can see there are receivers in both the front and the back ends of the backbone. The front one supports swapping multiple coupler types (say a traditional ball type or a 3-axis), and the rear one supports cargo racks, like a bicycle rack. The HF 18" receiver tubes are used to give the most bolt-able length. Of course you don't need to install the receiver tubes, you could just bolt the stock HF ball coupler to the front and do nothing in the rear if that suits your needs.

Shortening the frame means that the steel angle brackets for the angle tongue members and the spring mounting brackets will compete for space, but it turns out that the angle brackets can be eliminated and the front spring mount bolt can also serve to secure the rear of the angled tongue members. The angle brackets can be reused/redrilled if desired to secure the angled tongue members to the front crossmember, although in the frame pictured in this thread the angled members were simple through-bolted to the front crossmember.

[Image: FramePlan2.jpg]

One other common concern about the HF frames is the width of the axles - they just have enough distance between the wheel mounting surface of the hub and the frame side rail to fit the 12" wheels/21" tires that come with the frame. Most people want to run larger wheels and tires, perhaps even sharing a spare with their tow vehicle, so they think they need to get a new longer axle. It's actually a "glass half full", not a "glass half empty" if you look at it this way: the axle isn't too short, the frame is too wide Smile. Unless you absolutely need the full 4' of frame width for your application, you can easily shorten the frame crossmembers by 4" to result in 2" more tire clearance on each side.

One thing you will need to do to the axle if you decide to narrow the frame is to relocate the spring seats moving spring perches 2" inboard on each side as shown in the drawing below. This is the only place welding is necessary to do this modified frame, so even if you don't have a welder you can probably bring the axle to a welding shop and get this done for a few bucks.

[Image: FramePlan3.jpg]

If you're planning on running the same wheels and tires as your two vehicle, you may find this thread useful as well: http://tventuring.com/trailerforum/thread-64.html

Here are a few photos of the finished stronger 4x4 frame, notice it's got the same wheels and same size tires as the Jeep in the background:

[Image: Tongue1.jpg]

[Image: Tongue2.jpg]

[Image: BikeRack1.jpg]
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02-01-2013, 09:36 AM
Post: #2
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
Jeff, thanks for the detailed info on improving a HF frame. This shortened 4x4 version is what a Compact Dinoot can be built on.

Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping
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02-01-2013, 09:44 AM
Post: #3
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
(02-01-2013 09:36 AM)Scott Wrote:  Jeff, thanks for the detailed info on improving a HF frame. This shortened 4x4 version is what a Compact Dinoot can be built on.

Yes, in fact that's exactly what this frame was built for.

[Image: FinalTent3-1.jpg]
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02-01-2013, 09:46 AM
Post: #4
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
I knew it looked familiar Smile

Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping
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02-02-2013, 10:14 PM
Post: #5
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
Excellent job! You're truly the MacGyver of offroad trailers! You've got a great trailer on a HF budget! Did you make your own tub cover?
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02-03-2013, 05:02 AM
Post: #6
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
(02-02-2013 10:14 PM)Manuel Wrote:  Excellent job! You're truly the MacGyver of offroad trailers! You've got a great trailer on a HF budget! Did you make your own tub cover?
Thank you. It did work out to be a great frame for my Dinoot - very sturdy and it shares tires with my Jeep so I don't have to carry an extra spare for the trailer.

I've also designed a 6' version of the same modifications to the HF frame, I'll be posting plans for that as part of my next project.

Yes, I made the plywood cover. There are plans for DIY plywood covers for Dinoot trailers here: http://www.dinoot.com/index.php/building...hard-cover.
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05-25-2013, 05:51 PM
Post: #7
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
Great info!
Thank you for sharing this!

Thanks All & Cheers!
Gale
Link to my modified Explorer Box Build Journal.
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05-28-2013, 09:26 AM
Post: #8
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
When "shortening" the frame cross members to be narrower for larger tires, did you shorten both sides by 2" or one side by 4".

You seem to have a huge fully stocked workshop, so how did you choose to cut them down?
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05-28-2013, 09:41 AM
Post: #9
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
(05-28-2013 09:26 AM)BrianAg95 Wrote:  When "shortening" the frame cross members to be narrower for larger tires, did you shorten both sides by 2" or one side by 4".

You seem to have a huge fully stocked workshop, so how did you choose to cut them down?

I cut each side 2" shorter because it kept things like the stake pockets centered. Not that it matters, because the stake pockets weren't being used and they aren't visible underneath the trailer tub, but I just decided keep everything symmetric Smile. But you can just cut one side if that's easier for you, the end result won't be any less strong or functional, and you'd only have to drill new holes in one end.

They can be cut by hand with a hacksaw, or more easily with a cutoff wheel in an angle grinder. The angle grinder is probably the best method for most people, even if you don't have an angle grinder you could buy one for under $20 on sale and with a coupon at Harbor Freight: http://www.harborfreight.com/catalogsear...e+grinder.

I used a metal-cutting bandsaw because I have one in my workshop.
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05-28-2013, 09:49 AM
Post: #10
RE: Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
Thanks! I thought it looked like those stake pockets were still centered.
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