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Building A Trailer Hitch

Discussion in 'Bicycle Mechanics' started by StuInTokyo, Feb 16, 2011.

  1. StuInTokyo

    StuInTokyo Maximum Pace

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    OK, I have the new tow bike, the Mixer 8, but now I need to make a new hitch for it. On the Cannondale I had the hitch attached to the seatpost, this worked, but I have always been concerned of the potential damage I could do the the frame with the back and forth leverage from the seatpost attaching point.

    [​IMG]
    That is a close up of the existing hitch.

    [​IMG]
    A 165lb delivery


    Below is a quick mock up using some wood to give an idea of how I want to attach the new hitch, the size of the plates, the gussets and the hitch are will change, this is just a crude mock up, but I think you get where I'm going.....

    [​IMG]

    [​IMG]

    [​IMG]

    I'm looking for some comments, if you see something that sends up red flags, please do tell, I'm not married to this exact design, so I am looking for ideas.

    I will also say that I've looked hard at the hitch down at the axle and I find it not to be so good, I understand that with a fairly heavy load, which I will carry daily, the trailer usually does not track well, and turning in one direction is easier than the other etc.

    Comments please! :D
     
  2. kiwisimon

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    Stu can you use the eyelets already on the seat stays, with the bracket in between the stays? Would mean you need to build less.
     
  3. StuInTokyo

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    I could, but those are fairly small points, I'd rather spread the load around, I think this will be sturdier, I'm not worried about building less, after all I built that trailer :D
     
  4. yokotas13

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    if you do a three point brace to the rack mounts and brake bridge you will be fine. no need to overengineer it

    or just do like a burly is and do it at the axle.
     
  5. StuInTokyo

    StuInTokyo Maximum Pace

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    The guys at Charge bikes said to NOT use the bridge, they say it will fail, and besides, I want to use the rack mounting points to mount a rack :D

    Over engineering is what I do! Light weight is NOT the object here, durability is. I honestly do not think you can understand how heavy 150lbs on a trailer is, and the stresses it creates. I need to use this six days a week every week, so it needs to be solid and NOT fail :D
     
  6. yokotas13

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    why not use the same mount all the utility trailer guys (bikes at work etc etc etc ) and use the chainstay/axle setup everyone else has. no need to reinvent the wheel.

    After 6 months of trailer searching, only a handful used the seat tube area to mount, and none that i saw had a huge load capacity
    Id imagine there is some reason to it but im no engineer

    besides if you do it this way...you cant really use the top of the rack for a 24 pack if you ahd to
     
  7. Sikochi

    Sikochi Maximum Pace

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    I know it`s just a mock up and you said size will change, and that you are probably aware of this, but don`t forget clearance for your mudguards.
     
  8. yokotas13

    yokotas13 Warming-Up

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    i doubt he has any with his new huge tires. check the pictures he posted in the general section.
     
  9. StuInTokyo

    StuInTokyo Maximum Pace

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    From my research, I have found that most of the guys using a side pull hitch are not carrying much weight, usually less than 50 pounds, including the trailer. Most of them also have the weight above the axle. Keeping an axle and the weight above it makes for a lighter weight stronger trailer, but it has a very limited load carrying capacity, as the heavier the load, the more unstable it gets. With a heavy load, it is better to have the weight below the axle, this makes the trailer much more stable.

    Take a look at this post >> Here << this fellow is where I got the idea from to make the mounting point there.

    Also take a look here at >> Tony's Trailers << he has a lot of real world actual use info on trailers. The hitch up high is more stable and more convenient, seems to be the drum beat.

    Please keep challenging me and making me think about it all, that is what I need to do!

    Domo! :D
     
  10. StuInTokyo

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    Thanks for that mention, but Yokotas13 is correct, I have no space for fenders, I might just put a partial rear fender on at some point, but I won't be riding much in the rain, as when it rains I use the small van, my customers are not very happy when I deliver soaking wet cases of beer etc :eek: :rolleyes:
     
  11. yokotas13

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    http://www.bikesatwork.com/
    these guys are pretty much the industry standard in the US for cargo trailers..

    they use side mount...again. no need to reinvent the wheel
     
  12. StuInTokyo

    StuInTokyo Maximum Pace

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    Yes, I've seen their pages, they certainly have some nice extruded aluminum trailer :thumb: but I don't like their small wheels, they do that to keep the center of gravity of the trailer lower for better stability, and they make the trailers cheaper by keeping a solid axle, but I repeat myself :D

    Did you read the other pages? They have a lot of info on how, in their experience, the side hitch is not nearly as stable as the rear center hitch, or how the side hitch, with a heavy trailer puts a lateral force on the rear wheel, not something I'd want in a downhill corner. Just because something is the industry standard does not mean it is the best, it just means it is often the easiest and cheapest to build, so it is the most prolific.

    Cheers! :beer2:
     
  13. yokotas13

    yokotas13 Warming-Up

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    im interested to see where yours goes :)
     
  14. GSAstuto

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  15. kiwisimon

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    Stu, I am no engineer but I think you are over estimating the forces your draw bar is putting on the hitch mount. Why not just switch the hitch over from the C'dale? It works well and if the seat post can take your bulk directly it can easily handle the weight of the hitch. If it were me and I wanted to get the hitch lower I would bracket it to the eyelets that are there for racks and fenders. There is no way the drawbar can deteriorate them. No matter what I am sure it'll come up looking tops. How are the new tires? Oh and that cut tire can be repaired with a strong rubber patch (boot) glued over on the inside of the tire.
     
  16. ProRaceMechanic

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    Just an Idea

    Could you extend the arm all the way to the seat tube under the top tube. There seems like there will be too much stress riding on the one bond between seat stays and seat tube. Maybee a round clamp around seat tube coming out in the same angle and have extra supports with something connected to the rack mounts. You could always still use those holes for a rack if you have a long enough bolt. Not to mention the seat tube also has a seat post inside so you get the doulble butted effect.
     
  17. StuInTokyo

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    I have looked at going down to the seat tube, it would be strong, but getting a perfect fit would be difficult, it would need very close tolerances.

    I think I might just make up a very strong rack, and have it serve also as my hitch mounting point, and I could also set it up to use my panniers as well for when the trailer is too much.

    Some pics.....

    [​IMG]
    The mark on the stick shows where the hitch on the trailer is now, this is rather tall, so I'm thinking to modify the trailer (yet again!) to lower a bit where the hitch level is. On the Cannondale I am taking off from the seat post, so of course the hitch is quite a bit higher, with the Mixer 8 I'll be taking off much lower on the back of the bike, just over the wheel, I hope.

    Some kind of a rack might be what I want, need.....

    [​IMG]

    Just a crude mock up with thin strips of wood, but I think this could work, with another bit coming down and a flat carrying area it might work just fine.

    I'm also thinking of reversing the way the hitch hooks up, now the tie rod end joint is on the bike and that goes into the trailer, but if I leave the tie rod end on the trailer and have it go into the hitch, like on the back of the beefy rack I will build, then I have the rack to use, unobstructed when I want, but a spot to hitch the trailer too, if that makes sense :rolleyes:

    Cheers!
     
  18. StuInTokyo

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    A little crude drawing and I have this for an idea....

    [​IMG]

    I know it is just basically a rack, but it would be made out of square tubing and it would be very solid, the hitch would be below the deck at the rear, so when the trailer was not in use, it would not interfere with using the rack on the bike. To use my panniers I'd have to add additional mounts to the side of the rack, and most likely move them back, to get the heel clearance I need, as the chain stays are a bit short on this bike, but I think that would also be possible.

    I think this could be a very good solution, I'll have a good solid point to mount my hitch, I'll have a usable rack, even when towing the trailer and I'll have a place to hang my panniers.

    Sounds good, now I just have to build it :p

    Cheers!
     
  19. kiwisimon

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    Good luck and I like this much better.
     
  20. FarEast

    FarEast Maximum Pace Post Of The Week

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    Have you not thought of an attachement that conects at the bottom of the rear stays and uses the Quick release to lock in to place?

    [​IMG]

    The load doesn't have to be shared over multiple joints or angles and if it does fail then it doesn't require huge amounts of engineering.

    Also all of the forces are in one direction rather than multiple. Other ideas could be based around the hitch clamping to the bottom of the stays thus spreading the load over a wider area.
     

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