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Doing Hitches for Bike Carriers - Hitch Hauls - Mobility Chairs - Trailers

Discussion in 'Gen 2 Prius Main Forum' started by PriusCamper, Sep 3, 2022.

  1. PriusCamper

    PriusCamper Senior Member

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    Working on a hitch project right now and wanted to get some feedback. Currently if you want to mount anything to the back of your Prius you have to buy a big heavy hitch that mounts to the 4 tow bracket bolts under the rear of the car. Not only do they cost near $200 these days but it's like driving around with a 40 pound bag of concrete in the back of your car for the rest of its life.

    So today I bought one of these bumper mounted hitches that Harbor Freight sells for $21 and am installing one on my test Prius.

    upload_2022-9-3_18-23-7.png



    If all goes well I'll be repeating the process a second time and installing another one on my friend's Prius who just bought a hitch mounted bike rack to go with their electric bike. But first have to figure out what kind of hardware to use to mount the hitch to the bumper and then need to cut up the bottom of the rear bumper cover so the receiver fits perfect when it's done.

    PXL_20220903_232916004.jpg

    Obviously the easiest hardware would be giant u-bolts or pipe clamps. Alternatively, could drill through the bumper, but I think that would weaken the bumper in a collision, so we'll see. Am about to see what options are at the hardware store.

    Anyways, what are people's thoughts on all this? The owner has no plans to use this hitch for anything other than a bike rack, so it's not going to be an issue with tongue weight from too heavy of a load.

    Will also be adding to this post links to all the other PriusChat hitch discussions so future users can get all the info they need in this thread. If you'd like to help find and post those links, please do!
     
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  2. Tombukt2

    Tombukt2 Senior Member

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    I put that exact plate on my AE111 if you don't know by the then that's a Corolla about an '02 model I have that exact well it's not that exact one mine actually has the two little holes for the safety chains from a trailer which I do use when I pull my plastic trailer made by FLOE and there is a way there's a plate made by Reese that also has the one and a quarter square in it with a bolt flange maybe that's what your picture is of I haven't mounted one of those to a Corolla or a Prius but it would be the same procedure on the AE11 I just put a plate with the two holes and the holes for the ball and that was it and it's been on that it's still on that car working just fine so it should go great on the Prius
     
  3. Tombukt2

    Tombukt2 Senior Member

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    square u bolts. Closest to the square of the bumper you can get . Double nut with a lock nut . Braise the threads . So they can't back off and should be pretty much permanent need to be squeezed on there good and I'm not sure how this would Fair with a trailer but I would try it My 5x8 plastic f l o e goes really well behind my Gen 3 and my hidden hitch is not as heavy as it seems and I already had it so I just put it on the car I need one for my Gen 2 and this would be the perfect workaround
     
  4. Tombukt2

    Tombukt2 Senior Member

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    My metal bumper on the Corolla is very similar to the aluminum square tubing bumper repair on the Prius on the Corolla I've had 200 plus pounds on that hitch without any trouble I mean that is a gas car but so what I shouldn't make much difference so I've had 2000 lb in the 5x8 trailer or something like that that winds up being right around 200 lb on the tongue with no trouble just going down a flat road moving some stuff you know 10-12 mi no speeding down the highway or nothing crazy but the bumper in the hitch where the least of any of the problems the weight of the trailer snatch in the car around was more of an issue if you got it in certain situations
     
  5. Tombukt2

    Tombukt2 Senior Member

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    You can get some pretty nice hardened U bolts square type whatever the width to the top of that bumper is and you'd be set like some grade 8
     
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  6. SFO

    SFO Senior Member

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    Would be concerned about the potential for an "obscured license plate" ticket.
     
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  7. PriusCamper

    PriusCamper Senior Member

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    When I hauled a 250 pound wheelbarrow size woodchipper on a 1600 mile road trip I specifically built the rig so it would not obscure the license plate. But yeah, that is an issue for everyone with the ability to haul stuff on the back of the car because there's plenty of crazy cops that shoot first and make up a fake story to answer the questions asked later.
     
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  8. Tombukt2

    Tombukt2 Senior Member

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    My trailer was stuff in it blocks the tag on my 13 all the time sometimes for hundreds of miles so far down there in the southeast we haven't had any problems because if you can pull up alongside the vehicle you can see the tag I haven't even seen a cop do that but you never know. We've got some wild ones down here too but generally they don't bother Priuses they're out chasing Camaros and moms and minivans coming through school zones.
     
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  9. PriusCamper

    PriusCamper Senior Member

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    Yeah Prius is ultimate camo as long as you drive annoying slow in slow lane. Of course when it comes to cops in the US your best camo directly correlates to how little pigment in your skin you have. :'-(
     
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  10. Prius Rising

    Prius Rising Member

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    Hey camper if, you want to go with the 4 bolt rear hitch route I have 2 in stock leftover from last years build. I haul a cargo basket that houses my cooler/freezer and other supplies. The first one is a class 1 receiver that came with the car the next one if a class 2 receiver I got from E-trailer it's still brand new. I finally discovered a class 3 for the gen 2 sold by Prius Overlanding that's on the car now. I would cut you a sweet deal on either one and then you would't have to modify the bumper. (y)
     
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  11. ChapmanF

    ChapmanF Senior Member

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    For this kind of use (and for Hitch Hauls or mobility chairs, as mentioned in the thread title), I would consider a hitch like this to be about the worst possible.

    The bike carrier, mobility chair, or Hitch Haul might be carrying less weight than the tongue weight of a properly-loaded trailer. But they all put that center of mass out on a considerably longer moment arm than where the tongue weight of a trailer on a hitch ball would be. That ends up as a serious twisting force on the bumper reinforcement here.

    [​IMG]

    Meanwhile, the attachment of the hitch to that bumper reinforcement has its own moment arm of only a couple inches, the thickness of the aluminum piece, basically. Imagine extending the above illustration to where the guy is trying to pull from a point two inches above the floor. The long moment arm out to the carried load, divided by this very short one, means a large magnification of the twisting force being put on this aluminum bumper reinforcement.

    And it is not only static forces to consider. As the car goes down the road, hitting dips, speed bumps, and potholes, the mass of that bike, Hitch Haul. or mobility chair gets bounced up and down at the end of that lever, with accelerations that might be more than one g.

    And aluminum, unlike steel, does not have any certain amount of limited flexing that is 'safe' from causing metal fatigue. As I understand it, all of the flexing that ever happens to an aluminum part counts toward its eventual fatigue failure.

    For this kind of application (bike or chair or hitch haul way out on a long moment arm), one might be advised to start with one of the conventional two-point-mounted hitches and even mod it with a third attachment point further forward, so the mounting has a longer moment arm of its own.

    [​IMG]

    It shouldn't be really necessary to make the third-attachment mod from such stout stuff as that guy did. The hitch already has adequate weight capacity from its two original mount brackets, and the long third piece just needs to resist the twist. Angle, or even flat stock, oriented vertically, could have done the trick.
     
  12. alftoy

    alftoy Senior Member

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    Aluminum bumper reinforcement is exactly that, not designed for mounting hitches. Bad idea.
     
    #12 alftoy, Sep 11, 2022
    Last edited: Sep 11, 2022
  13. ChapmanF

    ChapmanF Senior Member

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    Well, it kind of is designed for collision ... the collision energy that goes into crushing the aluminum reinforcement is that much energy not going into the rest of the car.
     
  14. PriusCamper

    PriusCamper Senior Member

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    @ChapmanF Your point about the longer the lever, the more force/strength required is indeed the challenge. And the designers of Hitch Hauls and hitch mounted bike racks prefer a longer lever rather than a shorter one because it's less hassle for the person using the product. When I hauled a 250 pound chipper on my curt hitch on a 1700 mile road trip I addressed this by custom building a mount that had as short of a lever as possible with no gap between the chipper and the bumper cover and the chipper was wrapped in a tarp with moist kitchen sponges to prevent scratches on Bumper cover from the slight wobble at the hitch receiver.

    And because the mounts under the car for hitches are further away (longer lever) than the bumper mounts there's more force on them, which is why they use super thick steal in hitch mounts to address that. Your photo of that particular hitch may actually be thinner steel than what curt uses:

    upload_2022-9-11_11-10-52.png

    Meanwhile Overland Prius in Australia did something similar to what I'm planning for this project, but he replaced the aluminum bumper with steel and also custom welded arms that bolt into the traditional mounts for hitches so he has 4 solid mounting points (8 bolts total) that boosts his potentital tongue weight capacity in this thread here: #JimThePrius Overland Conversion in the making. | PriusChat

    185321_IMG_20200414_135707.jpg

    And to your point this rig of steal is less able to absorb the force of a rear end collision and will transfer more force to the rest of the vehicle when there's nothing mounted on the hitch. However, as we saw in a recent post on here, having a hitch haul or similar basket mounted to the hitch full of stuff is going to mitigate that issue by crumpling under the force of the collision in ways that will absorb more force than even the aluminum crash bar.

    That being said, I'm still interested in moving forward with this project on my own Prius to find out its limits before I recommend it to anyone else. I'm still figuring out how to weld in more strength to it, likely in similar ways as Overland Prius did it above. Of course not sure where to find the Subaru hitch that he found that matches up to the bumper mounts, or maybe he welded that himself when he welded in the underside mounts?

    But it's also possible that I'm going to think up something that's even more simple and straightforward that keeps the length of the lever as short as possible. Perhaps extending a 2" steel square pipe coming out of the front of the hitch receiver and extending to that 3rd mounting point / jack point that's in your photo, which would eliminate most of the downward rotational load on where the aluminum bumper bolts to steel hardware that bolts to the frame. Thoughts?
     
    #14 PriusCamper, Sep 11, 2022
    Last edited: Sep 11, 2022
  15. fuzzy1

    fuzzy1 Senior Member

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    I've been doing bicycle event support in my region for a long time, moving from the original roof rack to a hitch rack ten years ago, and haven't yet encountered any concern from police here or in neighboring states and provinces. Even when working with police at incidents. No fellow support drivers have reported any problems either. Outside of organized events, the only local case I'm aware of was on an episode of the TV fictional serial Grey's Anatomy, where the stopped character lacked 'white privilege' while crossing the mountains towards the series' supposed home in Seattle.

    Cross-country travel was a different matter. Returning from a 1.5 month journey to the far coast and back, I was pulled over in South Dakota. While the nominal reason and resulting written warning were for "obscured plate", it quickly became clear that the real but unstated reason was for "marijuana state license plate".

    And possibly he was already on the lookout for something specific. A day or two later, not too far away, several marijuana smugglers from my state very seriously beat and attempted to murder another trooper. They were later convicted, and variously sentenced to 10 to 45 years. The injured officer recovered and returned to capturing other smugglers.
     
    #15 fuzzy1, Sep 11, 2022
    Last edited: Sep 11, 2022
  16. ChapmanF

    ChapmanF Senior Member

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    I think that by itself could be a big improvement over the straight U-bolted hitch.

    The strut going forward to the 3rd mounting point could even be made of a couple sizes of pipe, one in the other, so as to be telescoping. It only needs to resist the pitch forces, not any fore/aft movement. With it telescoping, a collision can still mash the bumper reinforcement without that being transferred ahead to the 3rd mount point.
     
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  17. PriusCamper

    PriusCamper Senior Member

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    Private message sent to you! (y)
     
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  18. black_jmyntrn

    black_jmyntrn Senior Member

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    well... your goal isn't clear. either way, you go, regular hitch or elevated... you won't be able to get around adding 40lbs to the car.

    I have what you are trying to make already built with a winch mount built in just, what will you do leave everything exposed like that?

    like all else stated, it's aluminum, and at best it can withstand a tow hook and be pulled a few times before it will warp.

    this picture isn't a gen2 nor the rear but the only picture ive already posted online that I can share thats related to this topic...
    now, I just need a gen 2 for a few days to 3d can and mock up something.... too bad you are not in socal, we could've had this done for you in a few days...
    20210526_165008-01.jpeg
     
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  19. alftoy

    alftoy Senior Member

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    Same idea as RV bumper hitch.

    RV Bumper hitch - Google Search
     
  20. PriusCamper

    PriusCamper Senior Member

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    As of yesterday the hitch is finally installed... Finding the right material for an extension arm to eliminate rotational forces was the 2nd hardest part, but a client who was waiting for me to do a dump run set out a heavy duty steel Djembe drum stand in her free pile that was perfect.

    The extension arm fits tight up against the spare wheel well and doesn't require any fasteners because I welded it to the hitch, which was the hardest part because I've never welded before and only had 10 minutes practice before I welded this with an old beat up flux core welder that's the cheapest welder money can buy at Harbor Freight. I got it used for $75. These first welds are awful... Super ugly and embarassing. Hoping the weld fails so I can try again, but it probably won't.

    Anyways, enclosed are all the photos. Very pleased with how it worked out, weighs about 10 pounds and cost me ~ $30 for the hitch and the bolts, which is a huge savings now that hitches weigh near 4 times as much and cost 7 times as much. Still have to figure out if I'm going to make the hole in the bumper cover larger as well as how to treat the edges, perhaps a brake lighted 2" receiver plug is going to happen too?

    NewHitch1.jpg NewHitch2.jpg NewHitch3.jpg NewHitch4.jpg NewHitch5.jpg
     
    #20 PriusCamper, Oct 9, 2022
    Last edited: Oct 9, 2022
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