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  1. #1
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    Default Building myself a trailer, help with some info first!

    OK guys, Im about to start building myself a trailer for my Kart racing, since my last one is getting pretty old and tired, and its very hard to find something second hand that has what you want it to!

    Iv read alot of different threads on here and have found a few various answers to some questions, but am still a bit confused, so though if it was OK, id put all my Qs in this thread and gather as much info as possible.

    The frame layout i was thinking would be something similar to this: (sorry for the crappy paintshop drawing)


    Now, what size RHS would you recommend for the various parts above? red being the drawbar and rear chassis rail, ect ect... i really dont no how much the trailer will weigh, as it will depend on what size steel i use, however to give you a general idea, it will be a fully enclosed trailer, with a frame made of something lighter (i was thinking 20x20mm) about 1.7mtrs high with a few shelves ect inside and then fully cladded.
    It wont ever have to carry much loaded weight, the Kart (80), tools (50) spares (50) and fuel and misc, should only come to around 200kg, but say 250kg being generous

    Next thing, how do i work out where to put the axle / springs? and what rate springs would i look at getting? and while we are on axles, is there anywhere online i can look at purchasing this stuff, or where would you recommend?
    Is there any special way of working out what size and length axle to get?

    and lastly, how long would you recommend the drawbar extends out the front of the trailer section?


    Thanks heaps and sorry for all the questions, I have a fair bit of welding experience and love a mechanical / engineering challenge but just dont have a ton of knowledge when it come to the trailer specific stuff.

    Thanks again.

  2. #2
    Yonnee's Avatar
    Yonnee is offline Trailer Bloke & Mild Mannered Moderator
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    Quote Originally Posted by JB#3 View Post
    OK guys, Im about to start building myself a trailer for my Kart racing, since my last one is getting pretty old and tired, and its very hard to find something second hand that has what you want it to!

    Iv read alot of different threads on here and have found a few various answers to some questions, but am still a bit confused, so though if it was OK, id put all my Qs in this thread and gather as much info as possible.

    The frame layout i was thinking would be something similar to this: (sorry for the crappy paintshop drawing)


    Now, what size RHS would you recommend for the various parts above?
    Red - 75 x 50mm x 3mm...
    Green & Blue - 40mm SHS x 2.5mm...
    Top framework - 25mm SHS x 2.5mm...
    red being the drawbar and rear chassis rail, ect ect... i really dont no how much the trailer will weigh, as it will depend on what size steel i use, however to give you a general idea, it will be a fully enclosed trailer, with a frame made of something lighter (i was thinking 20x20mm) about 1.7mtrs high with a few shelves ect inside and then fully cladded.
    It wont ever have to carry much loaded weight, the Kart (80), tools (50) spares (50) and fuel and misc, should only come to around 200kg, but say 250kg being generous

    Next thing, how do i work out where to put the axle / springs?
    Set up your chassis first, WITHOUT drawbar,
    Axle centre should be 1/2" backward of centre for every foot of body.
    So, from your drawing and measurement, your axle centre should be 1730mm from the front cross bar.

    and what rate springs would i look at getting?
    Something around 700kg capacity.
    I'll have a look at my books when I get home and tell you how many leaf springs...

    and while we are on axles, is there anywhere online i can look at purchasing this stuff, or where would you recommend?
    I see you're in Melbourne...
    Melbourne Trailer & Caravan Supplies
    Ashley Park Drive, Chelsea Heights.
    9772 2333.

    Is there any special way of working out what size and length axle to get?
    Yes. But I need to know what wheels and tyres you're planning on running.

    and lastly, how long would you recommend the drawbar extends out the front of the trailer section?
    Minimum 4'.
    But 4'6" to 5' is better. The longer the point between axle centre and towball, the easier the trailer is to reverse.


    Thanks heaps and sorry for all the questions, I have a fair bit of welding experience and love a mechanical / engineering challenge but just dont have a ton of knowledge when it come to the trailer specific stuff.

    Thanks again.
    That's where I come in

    Are you building it for one or two karts?
    For the amount of effort to add a second tier for another kart would be well worth the future re-sale value of the trailer.

    Are you planning on a tapered section at the front for less wind drag? If so, make this part of the chassis, not just tacked on top of the drawbar.
    Too many projects, so little time, even less money!
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  3. #3
    Calm's Avatar
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    Being a former Gokart racer (champion*) i am not sure about your sizes. i suggest you lay the karts etc out on the floor as you want them in the trailer and measure around them. Remember that the gokart wheels maybe set wider at times. If it is a shelf trailer (2 karts high) allow extra between them (about 50 to 75mm). Also dont leave the karts sitting on their wheels in the trailer as the small movement (rocking) backwards and forwards wears out the rings and the bore.

    Any construction above the floor can be lighter as there is no weight much.

    Another thought remember access from the front

    i dont think i have any photos of my trailer but it used 2 modified rear subframes from a mini for suspession, It was on 10 inch wheels, tandem, load sharing suspension, very light and great to tow.

    Cheers hope that helps.


    * legend in my own lunchbox
    Last edited by Calm; 1st Oct 2008 at 12:44 PM. Reason: added *
    regards

    David


    "Tell him he's dreamin."
    "How's the serenity" (from "The Castle")

  4. #4
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    Yonnee, you are an absolute superstar, thats pretty much the exact answer i was dreaming off!

    Yes it will be built for two karts, one (when required) will be on the ground and one on an upper shelf. The right side kart shelf will continue down the trailer where there will be a work bench and a spot for some stacker draws ect. then around and across the front of the trailer for some general shelving.

    The trailer wont have a bullnose section as such, but will be "angled" down the front, similar to this: (just with out the nice fancy curve, just a pointy but joint instead.)




    Thanks for your help Calm,

    The measurements should be pretty much spot on, max kart width of 1400, plus the 50mm for the two SHS uprights leaves me with 50mm to play with when fitting the struts ect, however I may need to change that measurement once iv worked out how i am going to mount and seal the rear door.

    The will be a front access door on the left side, just in front of the kart shelf, which will be 2000mm long, oppersite the door will be the workbench shelf and stacker draws... with some general shelving going across the front.

    Thanks heaps for your help guys, any other advice will be greatly appreciated, i will get back to you sometime yonne about axle length when iv worked a few more details out.

    Now to chase up some $$$ and start getting some supplies... it will be a longish process, but I havnt got much racing left this year so will make do with my current trailer, my only aim is to have it done for the state titles in early Feb 2009.


    Cheers,
    Josh

  5. #5
    Calm's Avatar
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    Found a photo (actually the Daughter had one of her kart) - not very good of the kart trailer but you might get the idea.

    I built this myself and the straight front is the same height as the car towing it, so i got maximum advantage for storage and the slope was from the car roof line upwards -hpe that helps.

    Cheers
    regards

    David


    "Tell him he's dreamin."
    "How's the serenity" (from "The Castle")

  6. #6
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    Default Measurement alert...

    Something I just thought of while looking at the pictures above...

    I was assuming the karts would be placed near the front of the trailer. And therefore, with the weight of the kart/s in front of the normal axle position, this would not be a problem.

    But...
    loking at Calm's trailer, above, his karts were right at the back. Not so much of an issue with a tandem, but a single axle trailer with 200kg placed behind the axle, that puppy is going to want to swap ends with you on the highway!!! Or at the very least, get the sways up!
    Too many projects, so little time, even less money!
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  7. #7
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    Yehh, that is one issue my current trailer has, axle is to far forward... dusnt tow too badly, but it is bloody annoying when your at the track and sit inside the rear door and the thing tries to tip backwards...

    So i guess i have to move the axle further back... anyway i should work out how much? try and find the approx centre of gravity or something?

    Cheers,

  8. #8
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    Quote Originally Posted by JB#3 View Post
    So i guess i have to move the axle further back... anyway i should work out how much? try and find the approx centre of gravity or something?

    Cheers,
    Yeah, sort of. Have you got a pic of your current setup? How much different will the new trailer be, in size, etc.?
    If similar, you could probably move the measurement of the axle placement back about another 12" from your current one.

    Where abouts are you? Might be worth a look, and a chat in person. Could even assist with the build.

    PM sent.
    Too many projects, so little time, even less money!
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  9. #9
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    ok cheers mate,

    Im living in aspendale gardens, how ever we only just moved here and my current trailer is still at our old place, just moving also means the garage is full of just about everything that shouldnt live in a garage!
    So it will still be a little while before i get underway.


    Yon ill be in touch at some time regarding your PM

    Cheers,

  10. #10
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    You're kidding... How good's your arm? You could just about land a rock on Melbourne Trailers' roof from your place!!
    They're open Sat. mornings from 8:30 till 12noon.

    And I know what you mean about moving... nearly 4 years and I can still only get one car in the front garage... AND I HAVE A FOUR CAR SHED AT THE BACK!!!
    Too many projects, so little time, even less money!
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  11. #11
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    Quote Originally Posted by Yonnee View Post
    Something I just thought of while looking at the pictures above...

    I was assuming the karts would be placed near the front of the trailer. And therefore, with the weight of the kart/s in front of the normal axle position, this would not be a problem.

    But...
    loking at Calm's trailer, above, his karts were right at the back. Not so much of an issue with a tandem, but a single axle trailer with 200kg placed behind the axle, that puppy is going to want to swap ends with you on the highway!!! Or at the very least, get the sways up!
    Yonnee the gokart is the light bit. The fuel drums, spare motors & wheels, tool boxes etc at the front are the heavy bit.

    I would suggest a drop down leg at the back as a good way to stop it tipping up when you "walk" in. I forget but karts only weigh abour 60 or 70 KG complete without a driver - as a guide the classes are 130kg (light), 150kg (heavy - that was me 84 kg + kart + a couple of Kg lead to come in at 152KG), 170kg (super heavy) combined weight.

    Cheers
    regards

    David


    "Tell him he's dreamin."
    "How's the serenity" (from "The Castle")

  12. #12
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    Quote Originally Posted by Calm View Post
    Yonnee the gokart is the light bit. The fuel drums, spare motors & wheels, tool boxes etc at the front are the heavy bit.

    I would suggest a drop down leg at the back as a good way to stop it tipping up when you "walk" in. I forget but karts only weigh abour 60 or 70 KG complete without a driver - as a guide the classes are 130kg (light), 150kg (heavy - that was me 84 kg + kart + a couple of Kg lead to come in at 152KG), 170kg (super heavy) combined weight.

    Cheers
    Point taken... but even 140kg, for two karts, can upset the balance of a single axle trailer. And I'm guessing the heavy part of a kart is at the rear...

    If I was building a single axle kart trailer, I'd set the chassis and drawbar up on the floor, and then put a piece of timber/steel across roughly where the axle goes, and then stand on the chassis, adjusting the pivot point so it was balanced with my weight on the back. Then I'd see how that looks, and maybe play with it a little from there.

    Just goes to show, there's not always the same rules for building all trailers.

    I do agree with a drop down leg, a wind down caravan jack would be ideal, as they have a little wheel in case you bottom out the trailer on steep driveways.
    Too many projects, so little time, even less money!
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  13. #13
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    Yonnee your the ideas man
    regards

    David


    "Tell him he's dreamin."
    "How's the serenity" (from "The Castle")

  14. #14
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    Quote Originally Posted by Calm View Post
    Yonnee your the ideas man
    But I don't have a broom with a hose attachment!!
    Too many projects, so little time, even less money!
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  15. #15
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    OK this question was always going to come...

    to brake or not to brake...

    Im currently leaning towards brake, but just an over ride mechanical system (I plan on buying a new tow car next year, well nice big diesel van actually, but i also want to be able to tow with my daily driver, so i can take the trailer with me to work or whatever when needed) hence the reason i dont want electric brakes.

    Iv worked out the enclosed box section of the trailer will be about 1700 high, and in order to fit it under my garage door, allowing for 17inch rims with 205/45 tyres, and the actual chassis itself, it only left me 100mm to play with for the "bottom of chassis to center line of axle" distance (springs, hangers, suspension travel ect).

    So was thinking i should get an axle with 2 1/2inch drop stubs.

    Dose this make sense to you 'well learned' people out there? the above statement might be complete and utter BS... in which case just laugh it of and tell me so

    with average 1000kg 5leaf springs, what would be a normal "bottom of chassis to center line of axle" measurement?


    Thanks guys,
    Josh

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