Downhill kart for the kids in the making.

  1. mroek Member

    Messages:
    19
    Haugesund, Norway
    I'm currently working on a downhill kart for the kids. Thought I'd share the progress. When I first made the chassis, I soon realized it was waaaaay too big:

    [​IMG]

    I had to make it narrower:

    Front:
    [​IMG]

    Back:
    [​IMG]

    My plan was to keep the steering bits in front of the front axle to keep it out of the way:

    [​IMG]
    [​IMG]
    [​IMG]

    Although the angles of the steering was technically correct, it was not a good solution mechanically. The ball links hit their limits, and in general it felt just wrong, so I gave up, and moved the steering rack behind the front axle instead:

    [​IMG]

    I've actually made a rack-and-pinion steering with a bicycle gear (11 teeth) a bit of bicyle chain welded to a section of square pipe, and as a bearing I've used a ball bearing drawer slide. I had to modify it slightly to make it go both ways from center, but that wasn't difficult.

    The finished steering:

    [​IMG]
    [​IMG]

    Then I decided I needed a roll bar, but since I had no round pipe I used square pipe for that too. I did cut some wedges in it though, to make it look nicer:

    [​IMG]
    [​IMG]

    I also made pedals, and although there will be no engine (at least not yet) I decided to make two pedals just to be future-proof. I will connect the pedals so that both of them will operate the brakes on both rear wheels:

    [​IMG]

    Next up is to make the brakes. It will be wheel brakes, with a braking shoe operating directly on the rubber of the tyre. Will of course be hard on the rubber, but it's the easiest solution. At least for now.

    As you can see the seat is actually a modified plastic garden chair, and it is lengthwise adjustable to accomodate both children and adults (why shouldn't adults have fun too... :-))

    Comments and critique welcome...

    Regards
    -Øyvind
     
  2. storm monkey

    storm monkey Cluless Expert!

    Messages:
    209
    Cumbria - UK
    Looks fantastic so far. Makes we wish I had kids, almost. I'd go for a stronger seat, though. Not so much for the kids, but the adults may find it a bit flimsy unless you can strengthen it.

    Another method I've used for the steering is to mount a pully instead of the cog, on the steering column, and run a cable from one track rod end, round the pulley, twice, and attached on at some point, then off to the other track rod end. Of course, you also need a solid link between track rod ends too. Bike break cable does the job.

    Phil
     
  3. Wozzaaah

    Wozzaaah The wizard of woz Staff Member

    Messages:
    14,336
    Wiltshire, UK
    Excellent work Øyvind, really impressive project. I'm with Phil on the seat, that one will do but it would look nicer and be safer with a better one. You might even be able to get hold of a proper go-kart one for next to nothing if you ask around.
     
  4. MrFluffy Member

    Messages:
    2,911
    Location:
    In the shed
    Childs safety seat with the padding removed is cheap and easy and strong, especially if its a bit skanky and comes free as a result. You only need the rigid plastic bit ;)
    Ive got the one from my little one's baby period stashed for this application and I can squeeze myself into it, so should be fine for son.
     
  5. MrFluffy Member

    Messages:
    2,911
    Location:
    In the shed
    Id also gusset the spindle carriers a bit at the front as at the moment theyre only supported at the top, it will help it stop cracking with load for not a lot more weight...
    If you use say 3mm plate the weight penalty wont be much.

    Bit like the yellow bits:-
    [​IMG]
     
  6. peterd51

    peterd51 happy to be here!

    Messages:
    1,593
    Scunthorpe UK
    Hi,

    nice piece of kit!

    Is it your own design or have you followed plans?

    When you say, 'downhill', is the idea to take it up a hill and push it off to freewheel down?

    Regards
    Peter
     
  7. mroek Member

    Messages:
    19
    Haugesund, Norway
    Thanks for your comments!

    I do agree about the seat, but I am planning to add safety belts that will be attached to the frame, so I don't really think the seat will break. But in any case, it should be easy to modify the seat carrier to allow mounting a different seat if I should find one.

    @MrFluffy: I agree that it is probably a good idea to strengthen the spindle carriers a bit, but at the same time I really don't think the existing ones will break. I'll ponder some more about it.

    When I say downhill, I mean there will be no engine, so the kids will have to push it around. I have thought about maybe adding an electric motor though. Maybe later.

    There are no plans other than those that form in my head as I go along. As you can see, I've had to do modifications along the way due to bad choices.
     
  8. mroek Member

    Messages:
    19
    Haugesund, Norway
    Update, brakes added

    Unfortunately the wheels would need serious modification if I were to add proper brakes, so I decided to make brakes that operates directly on the tires.

    It doesn't look too bad, but unfortunately the brakes were a bit ineffective, so I will need to redesign some. I haven't decided what to do yet, but it's either more leverage (it's about 0.8:1 pedal to brake shoe as it is today) or some kind of lining in the brake shoes. I can't think of any suitable substance, though.

    If I shorten the arm on the brake shoe itself, I will at some point get self-locking brakes (ie the brakes will jam), which is not good, but perhaps there is a middle point where this effect can be utilized without jamming?

    Pedals are now locked together:

    [​IMG]

    Brake shoe and return spring mechanism:
    [​IMG]
    [​IMG]
     
  9. MrFluffy Member

    Messages:
    2,911
    Location:
    In the shed
    Bolt on discs from a pocket bike with cable actuated calipers. I think your main problem there will be the strength of the wheels to take a brake mounting.
    You could change just the rear wheels for some with some more strength if you take this route (maybe the pocket bike ones :D ).
    Could also do a big lever that jams into the ground and lifts the rear wheels instead. Itll trash your driveway or garden, but it'll stop quick ;D


    You can bolt direct to the wheels and see how it goes for now. You'd be amazed what you can get away with, I machined up a v pulley and sandwiched it onto a plastic wheel with a plate the other side of the sandwich for strength for this :-

    [​IMG]

    Its coming along nicely, i should add since I always forget that bit :D
     
  10. mroek Member

    Messages:
    19
    Haugesund, Norway
    I shortened the arm to the brake shoe a little bit (about 3 cm), curved the shoe a little more to make it grip the tyre better, and also made a better wire clamp. That did the trick, and it is now braking just fine.

    [​IMG]
     
  11. pedrogp New Member

    Messages:
    1
    Lima Peru
    brakes

    You could try direct to the soil brakes, kind of two levers going down on each side so that the kart will be suspended on them while braking, some ruber under them will also improve braking
     
  12. Have you considered adding a small piece of soft wood between the break surface and the tyre.
    Won't last long on heavy breaking but should give a bit more initial bite on the rubber than bare steel.
     
  13. Aus-Fitter Member

    Maybe put a couple screws through the brake plate. Will probably go thru tyres at an amazing rate, but should stop relativly well I think :D

    Looks great anyways :) My dad built me one of these, using a P handled sack truck layed parallel to the ground as the chassis, added a front axle to the P section and welded a seat on there, presto little billy kart. Man there is some good memories from that thing.

    CHEERS
    Ryan
     
  14. cookie munsta

    cookie munsta Member

    Messages:
    175
    australia
    i'd ****** the seat off i've broken a few just by leaning back with a stubbie 'pint'. it works good now but if you stack it you might want more support
     
  15. pedrobedro

    pedrobedro Man at Matalan

    Messages:
    9,838
    Location:
    CX Derbyshire
    It's definitely worth a proper kart seat if you come across one. I'd put a bar across the front to join the tops of the steering together if the grown ups are going to use it as well. Tillett kart seats sometimes come up cheap on ebay if you look around.
     
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