Homebrew powered trailer dolly

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Homebrew powered trailer dolly

Post by WoodIsGood »

I wasn't willing to spend a grand on something to move my trailer around so decided to design and build my own powered dolly. It's powered by a 3,000 lb Harbor Freight winch ($60 on sale). Wheels were $4 each at Harbor Freight. Sprockets are worn discards from Woodglue's 250R (thanks for the donation!). Used battery was donated by a mechanic friend. Grade 8 all-thread rod and various other hardware from McMaster Carr. Steel was mostly surplus/used bought at $.50/lb. Welding was done with help from a friend. I didn't keep receipts, but total cost was in the $150 neighborhood. Obviously it still needs some work (such as battery post to wing nut adapters) but it's in working order.

I have a receiver on the trailer for the post on top the dolly. It pushes my 16' tandem axle box trailer - loaded weight about 4,500 lbs - over a 2x4 placed behind a wheel on level concrete. Haven't had the chance to try it going up the driveway, but expect it to work fine.

A few hints in case someone wants to try this. Amperage draw under heavy load is over 25 amps so you need a big battery. Use thick wall material for the post and receiver or things will bend. Traction is related to weight on the dolly, so you might need the coupler to be back a ways on the tongue. Having low tire pressure does give you better traction, but also may result in torn off valve stems. #-o
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Re: Homebrew powered trailer dolly

Post by Mudkattgowfo »

That is so way cool........I may have to build something like that if the place I store at shrinks the rows anymore as my Truck has issues with turning.........Great job........

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Re: Homebrew powered trailer dolly

Post by Glamisbound »

I'm impressed!
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Re: Homebrew powered trailer dolly

Post by Woodglue »

Nice! =D>
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Re: Homebrew powered trailer dolly

Post by PWR MAD »

That's awesome, but how well does that winch with the "stock" cables on it? I have the same one on a mount I made for my toyhauler, with a lot of help from a good friend, that really struggles to pull a 1950lb. car up the ramp.
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Re: Homebrew powered trailer dolly

Post by WoodIsGood »

PWR MAD wrote:That's awesome, but how well does that winch with the "stock" cables on it? I have the same one on a mount I made for my toyhauler, with a lot of help from a good friend, that really struggles to pull a 1950lb. car up the ramp.
You might try running heavier and/or shorter wires from your battery to the winch. My guess is you aren't getting the necessary electrical power to the winch. It wouldn't surprise me if under a heavy load the motor would like to see 50 amps, and with that kind of current you'd only see about 9 volts at the winch with a 15' 12 gauge wire run.

In my first test of my dolly I used a really small 12v battery I had sitting around (10 amp-hr capacity?) with my 25 amp battery charger hooked to it to power the winch. Under any significant load the charger jumped to a full 25.7 amp, 14.5 volt output and it would NOT drive over a 2x4 behind a trailer wheel. A mechanic friend suggested I needed more current and gave me a 5 year old starting battery (it's not a deep cycle) he had sitting around his shop. With that battery and no charger hooked up (so pushing around 12v, not 14.5v) it groans a bit, but drives right over the 2x4. I'm curious what the amp draw is, but I don't have a way to measure that much current flow.

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Re: Homebrew powered trailer dolly

Post by PWR MAD »

I've cut it down to where it just reaches the fuse panel shown in the picture, where it connects to a 35 amp post. But you're probably right, in that I may need to increase the wire size. I'm running 4 of the NAPA 135 a/h golf cart batteries, but may be too far away at the panel. If it is maxing out the circuit, I may have to find a better way to power it. Thanks for the info =D>

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Re: Homebrew powered trailer dolly

Post by WoodIsGood »

In using the dolly today to push my trailer up the driveway and turning sharply at the same time (lots of added strain due to tandem axle trailer) I broke the top post loose. I had already decided that the post wasn't beefy enough and had purchased material to make a heavier post and receiver (for the trailer). Now I see that .120 steel wasn't heavy enough for the top cross-member either. I'll just add some 1/4" plate to the top of it when I replace the post and all should be good.

BTW, the winch motor was pushing strong with no sign of lugging when the post broke.
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Re: Homebrew powered trailer dolly

Post by Woodglue »

Glad to hear that the motor pushed it up your driveway. I was curious how it was going to do with that. =D>
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Re: Homebrew powered trailer dolly

Post by GlamisSandDuner »

Very cool John =D> . Your budget power trailer dolly is very impressive. After you get it repaired and beefed up you will have to post a video of it in action :wink:
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Re: Homebrew powered trailer dolly

Post by PWR MAD »

That's good to hear, about the power to push it up hill =D>

I've shortened the leads on my winch and with the snatch block (can I say that on here? :oops: ) it should do much better.

Thanks for the update, it sounds like you're on the right track =D>

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Re: Homebrew powered trailer dolly

Post by Woodglue »

:-k Once you get all the bugs worked out, would you make another one for a ASA member?
If so, how much would you charge for it?
I don't need one, but I'm thinking it might be a cool way for our BBS community to support eachother.
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Re: Homebrew powered trailer dolly

Post by WoodIsGood »

Woodglue wrote::-k Once you get all the bugs worked out, would you make another one for a ASA member?
If so, how much would you charge for it?
I don't need one, but I'm thinking it might be a cool way for our BBS community to support each other.
I'm not interested in going into production on these for several reasons. The main ones being that I don't weld - all the welding was done by a buddy as a favor. And my shop is set up for woodworking, not metalworking - all the cutting was done with a sawzall or hand held angle grinder, which made the cuts that had to be really square for the driveline a royal pain to make.

But I'd be flattered to let someone copy what I've done and very willing to lead them through the project. If anyone is interested in building their own I can post more photos and more detailed construction info. Otherwise I won't bother wasting my time. I'd even have a set of used 250R sprockets and chain to give someone for the project except that the friend replacing them threw them in the trash before I knew they were available. #-o

I spent about 3 hours yesterday cutting and prepping things for the modified "post and receiver" to replace the broken bits (no, I'm not very fast). Now I have to wait until my buddy is available to do some more welding for me.

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Re: Homebrew powered trailer dolly

Post by Dunerdave »

Off subject a bit to Power Mad.

The cabinet in the background of your picture shows a hinge that I have been trying to match for about a year. Can you tell me where togot it?

Thanks.

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Re: Homebrew powered trailer dolly

Post by PWR MAD »

Dunerdave wrote:Off subject a bit to Power Mad.

The cabinet in the background of your picture shows a hinge that I have been trying to match for about a year. Can you tell me where togot it?

Thanks.

Dave
It's original to the trailer, a 2008 Attitude, so I'm sorry I don't know.

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Re: Homebrew powered trailer dolly

Post by Dunerdave »

Thanks for letting me know.. at least it confirms the hinge is still available.

D.

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Re: Homebrew powered trailer dolly

Post by WoodIsGood »

Here are the details so anyone can copy my dolly design.

Post and receiver are Schedule 80 pipe - 1.5" and 2" respectively - with .25" plate and 3/16" bolts for receiver mount. Weld a disk on top of the post tube and weld a raised dot on the center top of that disk (to reduce turning friction). Grease the post to make turning easier. I have less than 10% tongue weight so had to mount the receiver as close as I could to the trailer box to increase the weight on the dolly to get enough traction so the dolly doesn't spin.

Dolly main horizontal member is 2.5" square .120 steel tubing with a .250 plate welded on top to strengthen the post attachment area. Could use thicker tubing and omit plate if desired. Remainder of tubing for dolly is .090 wall - 2x2 (winch supports), 1x2.5 (main vertical tubes), 1.25x1.25 (leg and handle receivers), and 1x1 (everything else). In the last photo below you can see that I ran the winch mounting bolts through a piece of 1/4" plate instead of the washers I was using earlier - the washers weren't strong enough for the load. The longer the handle is the easier it will be to turn the dolly when under load. Ground clearance for the battery end of the dolly is an issue when going from the driveway to the street. Raising this up a bit might be good - I have to use plywood under the dolly to cross the gutter. Don't raise things too much though or you'll have interference with the trailer tongue.

Wheels are 10" diameter from Harbor Freight - part # 30900. Use denatured alcohol or other solvent to clean the waxy film off the bead of the tires to help prevent the tires spinning on the wheels under heavy load. Also pump the tires to at least 30 psi for the same reason. Ignoring this advice will likely result in tearing the valve stems off the tubes (DAMHIK). Spacers between wheels are 2.5" .120 square tubing - make sure the ends of these are really square. Allthread and nuts for wheel assembly is 5/16", grade 7 with double nuts on both ends (McMaster Carr is a great source for this kind of stuff). Axle is 5/8", grade 8 allthread. Valve extenders are poly tubing and valve stems from old bicycle tubes with tie-wire "clamps." This is functional, but could really be improved on. Remove the cores from the tire valve stems if using this method.

Sprockets are used 13/39 atv sprockets. I didn't have the chain that went with the sprockets so purchased roller chain from McMaster Carr. This chain is for wider sprockets, but seems to work just fine and was a ton cheaper than a new ATV chain. Winch is 3,000 lb Harbor Freight winch #95912. Measure length of spool, then cut about 3/8" out of center of spool to allow room for drive sprocket. Use 1.5" .120 wall tubing for slip fit over spool (have to sand away some powder coating to make this fit). Good alignment is important when fabricating the sprocket assembly. I welded both tubes on the sprocket first. Then slid the drive-side half of the spool in and welded the tabs on while it was all clamped together. Use 3/16" flat head bolts to connect spool and sprocket assembly. Idle side of spool is just friction fit - using some JB Weld to solidify this might be an improvement. Make sure spool length is correct when done.

Here's some photos to help visualize the assembly:

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[edited by Woodglue 03/18/10 @ 10:02a - stacked pics instead of next to eachother to prevent page bl :shock: wout]

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Re: Homebrew powered trailer dolly

Post by Woodglue »

Cool! =D>
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Re: Homebrew powered trailer dolly

Post by WoodIsGood »

I put my dolly to its biggest test yet today, moving my trailer about 175' with all of that distance being up hill, turning, or both. Turning is actually more of a strain than up hill due to the scrubbing of the tires on the tandem axle trailer. It pulled/pushed great for the first half the distance, then started bogging down some. Towards the end it was bogging considerably, but still going. Out of curiosity I put my 25 amp charger on it, and it immediately was back to running really strong over the same ground it was really bogging down on just a minute earlier. This tells me I could use a bigger battery, or pair of batteries, to provide a higher current flow and/or reduce the voltage drop.

I didn't think to check how hot the wires were getting to see if I need a bigger gauge wire. I did check the winch motor a few minutes after I was done, and it was almost 150 degrees; so the motor, which is designed for intermittent use, is clearly being worked towards its limits.

PWR MAD, you might also try running your generator and battery charger - if you have such - to see if it helps your winch pull your car into the trailer.

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Re: Homebrew powered trailer dolly

Post by Woodglue »

Very nice! No matter what kind of probs it gives you, as long as it does the job you're still money ahead!
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