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How-to enhance a Harbor Freight frame for use under a DIY Camping Trailer


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Scott

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#1
This thread is for a discussion about using Harbor Freights Haul-Master #62647 1720 lb. capacity super duty 4’ x 8’ frames as a base for Compact Camping trailers. 94564 was the previous discontinued part #. The current #62647 version version has a fold in the middle feature.  For home-built camping trailer projects, this folding feature will not be installed.   By not installing the folding hardware, picking up a few extra bolts and bolting the two halves together, you actually stiffen the frame up some.  This is no big deal, the folding hardware is easily removable and the two halves can be bolted together like with the #94564 version.

[Image: 34865822833_c77af3e2fc_c.jpg]
 
From my experience they work well for camping trailers that will see pavement and occasional well maintained off-pavement towing with little to no modifications.  They are also suitable for light duty off-pavement towing, what I would refer to as Soft Roading with various levels of modification.
 
This discussion is for the Harbor Freights Haul-Master #62647 frame kits.  To get the question out of the way; why not the less expensive 1195 lb. capacity 4’ x 8’ kit?  First: the tongue attachment brackets are welded to the frame rails reducing flexibility in modifying it.  Second: the C-channel style axle used is notably weaker.  Finally: the frame come with 4 lug wheels. 
 
From a strength of materials perspective; the frames are up to the task of being bases for DIY camping trailers.  They are engineered for a 1980 lb GVWR (loaded weight).  The compact sized trailers we are discussing here normally have a loaded weight of 800-1200 lbs, some a little more, some a little less.  Also adding a trailer tub or box on the frame adds rigidity and strength.  The stresses of off-pavement towing do require making some modifications to maintain appropriate strength.

Here is a thread I started a while back to capture "real life" Long-Term HF style frame performance information

Here is an index of main topics in the thread:
Reducing the Deck Size
Improving the Tongue Strength
Improving the Ride Quality
Welding Frame Joints
Rear Stabilizer Jacks
Larger Tires
3500 lb Axle Tip
Wheel Bearings
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

Scott

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#2
Reducing the Deck Size

The majority of Compact Camping Trailers built on HF frames will have a deck footprint smaller than 4’x8’. Generally they are shortened to around 6’ and in some case also narrowed.

Modifying a HF frame requires basic DIY skills. Modifications include revising the frame parts layout, trimming pieces, and drilling new holes. Here are the tools necessary to make the modifications:
- Tape measure
- Couple clamps
- Hack saw at minimum, although a 4.5” angle grinder with cutoff wheel goes much faster
- Drill with 7/16” & 1/2” bits

Here is a 4’x6’ example planned for pavement towing and a 44”x72” intended for off-pavement towing
[Image: 35544789851_2c3eef2733_c.jpg]

[Image: 35506076222_b31008aec3_c.jpg]

HF frame decks are assembled from two 4’x4’ sections. For shortening, the rear section gets cut down to your desired length.
[Image: 35506109882_c8e55765ed_c.jpg]

For narrowing, you need to take equal amounts off the end of all cross members and re-drill the attachment holes.
[Image: 35506125742_5aabc13dc9_c.jpg]

Here is a PDF guide for converting to a 4’x6’ frame deck; Bolt-together frame kit guide for Explorer Box Camping trailers
Here is a post on converting to a 4’x4’ frame deck; Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

Scott

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#3
Improving the Tongue Strength

For off-pavement towing, the HF tongue design is on the weak side.  The tongue tends to twist when traversing uneven terrain and ditch crossings.  The fix is adding a backbone / new tongue that extends the length of the frame and out through the coupler plate.

Do this by using a length of 2”x2” .120” wall square tube to make the backbone.  The coupler plate gets flipped and the 2”x2” tube passes through it.  The backbone gets bolted to each of the cross members and the coupler plate.  The backbone extends past the end of the coupler plate approximately 1’ to form the new tongue.

You need to insure the backbone / tongue is centered on the frame.  Begin by marking the center of the rear cross member and centering the backbone over it.  Then measure from the front of the tongue on each side to the front of the spring hangers.  Adjust position until distances are equal.  Clamp securely in place, double check measures, drill your holes and bolt in place.

[Image: 35675108655_120bf7ed99_b.jpg]

[Image: 35675111055_71ca667cf7_c.jpg]

[Image: 35675112485_1f60f51bb1_c.jpg]

The link mentioned earlier, Building a stronger 4'x4' frame out of a 4'x8' Harbor Freight frame, shows how to reconfigure the extra pieces from a HF frame kit into a frame backbone / tongue when doing a 4' long deck.

[Image: 35675114975_9ab3f80d08_b.jpg]
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

TOM R67

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#4
IMO if you have welding ability, I should build your own from scratch, I thought modding the hf trailer would save time, it did not, plus I did not use the wheels or springs, and I will probly upgrade to an axle with brakes

I may even go back and nix the hole hf trailer and just build my own

If you look at my build the rear platforms are OK to step on cause I braced them to the box, the front platforms move if I step on them, looking into this showed the hf trailer flimsy c channel is flexing

Scott

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#5
I agree, if a person has fabrication skills & tools, you will end up with a stronger frame for only a few more dollars.
As noted earlier, the HF frames have their place based on the requirements of your trailer project.
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

Scott

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#6
Improving the Ride Quality

The HF Super-duty frames loaded capacity is just under 2000 lbs. For the lighter weight of compact camping trailers, this exposes a weakness, overrated springs. Even loaded to capacity the stock HF springs tend to be on the stiff side. So with a notably lower loaded weight than the rated capacity of the springs, they will ride rough. Because overly stiff springs don’t flex, they transfer more jarring and stress to the frame.

There is a remedy, replace the springs. To make this easy, I’ve developed a Smooth Riding Spring Retrofit Kit. The kit use a double eye spring that is about 9” longer, has a flatter profile and actually compresses for a notably improved ride. The new springs give your trailer a 1150 lb loaded weight capacity (GVWR). It comes with replacement spring hangers that are bolted on similar to the stock one.

There is an additional benefit from upgrading to this style spring, no more annoying banging from the factory loose fit slipper style rear spring mount.

Old verses New
[Image: 35675254655_48c2ee21d8_b.jpg]

[Image: 35675257555_23d30894c8_b.jpg]

With the axle installed over the springs, ride height is about the same as the stock HF setup. With the axle under the springs, you get around 4” of lift.
[Image: 35675319815_94879d83a6_c.jpg]

[Image: 35545090821_07697d60bb_b.jpg]

New Flash Jul '17: New and improved Smooth Riding Trailer Springs!

These are a premium spring with a longer overall length of 31", smoother ride and available in a 1175 lb (2 leaf) and 1450 lb (3 leaf) GVWR / load weight. More details on them under Trailer Frame Parts in our store. Available in separately and spring kits.

[Image: 35754040932_09bdbbb239_c.jpg]

[Image: 36432391905_2713e1bd7b_c.jpg]
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

Scott

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#7
Welding Frame Joints

Many style trailer boxes are designed to sit flush on top of the frame.  The protruding corner and cross member bolt heads create a small problem with this.  One fix is drilling flat bottom counter sunk clearance holes in the tub or box.  Another one is welding the top joints so you can remove the bolts.

[Image: 34867683033_084f82a91e_b.jpg]

[Image: 34867683713_2dc41090c7_b.jpg]
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

Scott

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#8
Rear Stabilizer Jacks

If you plan to Tent Top your Trailer, rear stabilizing / leveling jacks are useful. One way of attaching them is to bolt them on the rear cross member.
[Image: 35289779520_1904b9d595_c.jpg]

If you plan off-pavement towing, you can make brackets which angle the jacks in to better protect them.
[Image: 35289780290_d48b9e0733_z.jpg]

Here is another way of attaching rear jacks on a Harbor Freight frame by making brackets from 2" angle iron.
[Image: 36186815271_f869b096bd_c.jpg]

[Image: 36186814371_684152d45d_c.jpg]

[Image: 36186813661_df8d4261fd_c.jpg]
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

cerddwyn

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#9
(09-04-2015, 07:24 AM) Scott Wrote: Rear Stabilizer Jacks
...

If you plan off-pavement towing, you can make brackets which angle the jacks in to better protect them.

[Image: 35289780290_d48b9e0733_z.jpg]


I would also note that this method probably adds a modicum to the stability of the joint.  My plan is to use a slightly heavier grade of steel here to reinforce the corner welds.  My 2 cents.

Scott

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#10
(09-04-2015, 04:13 PM) cerddwyn Wrote: I would also note that this method probably adds a modicum to the stability of the joint.  My plan is to use a slightly heavier grade of steel here to reinforce the corner welds.  My 2 cents.


Yes good point, triangulating the corner that way would and same extra strength
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

 
 
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