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  1. #1
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    Default Building, rebuilding a trailer.

    I have been planning to rebuild my trailer for nearly a year, gathering stuff
    and drawing up plans. This rebuild means a new larger 8 x 5 chassis, A-Frame,
    dual axle suspension and hydraulic brakes. The old box and crossmembers sans
    floor cut in 4, welded on top and the gaps filled in. Floor will be replaced
    with 3mm checker.

    The suspension is from a 24 ft caravan. 39mm axles. My plan at the moment is to
    have drop axles. The ends of the axle will be strengthened with the thickest
    wall 50mm RHS I can fit on. This will then pass thru drop plates and be welded
    both sides. The RHS will extend inwards past the Ubolts.

    Stub axles will be hilux dimensions and will also pass thru drop plates with a
    shoulder for location and to keep square. Current design calls for 83.5mm
    between centres for the drop. Is this too much? What thickness drop plates
    would be suitable? The plan is for max load capacity. . The drop is to get the
    coupling at 450mm height to match both vehicles. Did I read somewhere that
    there is a max height for coupling mounting?

    I will make the stub axles. I will fit hylux disk hubs (genuine) and brakes. I
    will use sunrasias and off road tyres.

    I have a lot of this stuff because my wife bent our old ute like a banana
    around two big redgums about forty feet apart and did not touch the ground in
    between. Bent herself badly too. Nobody has ever told us exactly how many
    broken ribs. Many is all we heard.

    I have been thinking about making it a tipper. I have seen plans here similar
    to my idea with the A-Frame pivotting just forward of the front axle (may have
    been single axle). I have a large hydraulic ram and a pump arrangement which is
    driven by a 12v motor. forward to go up, reverse to go down. A mate used it to
    carry 4.5 cu m sawdust. It tipped that with pivot at back edge. To get 45 deg
    on my trailer will mean rear wheels well off the ground. Its just an idea at
    the moment. Any suggestions?

    The suspension as fitted to the caravan was eye to eye rocker with eye hangers
    at front and rear and both sets of shackle plates on the rocker. On the AL-KO
    web site I have just seen an arrangement with the rear spring fittings reversed
    so shackle plates are at the rear of both springs. What are the pros / cons for
    each arrangement? How do you work out exact positioning for hangers? I don't
    want to just assume they were correct to start with. A general question. What
    are thoughts on slipper springs? I don't like them myself and my son had them
    replaced on a tradie trailer because they caused him grief once too often.

    Springs 45mm x 6mm 8 leaf - One end has two leaves wrapped around eye?
    Chassis and A-Frame 75 x 50 x 3 RHS
    Cross beams 50 x 50 x 3 RHS
    Front and rear tailgates removable and will lay down to provide a level surface
    right thru.

    All suggestions appreciated.

    Dean

  2. #2
    Yonnee's Avatar
    Yonnee is offline Trailer Bloke & Mild Mannered Moderator
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    Default

    Quote Originally Posted by Oldneweng View Post
    The suspension is from a 24 ft caravan. 39mm axles. My plan at the moment is to have drop axles. The ends of the axle will be strengthened with the thickest wall 50mm RHS I can fit on. This will then pass thru drop plates and be welded both sides. The RHS will extend inwards past the Ubolts.

    Stub axles will be hilux dimensions and will also pass thru drop plates with a
    shoulder for location and to keep square. Current design calls for 83.5mm
    between centres for the drop. Is this too much? What thickness drop plates
    would be suitable? The plan is for max load capacity. . The drop is to get the
    coupling at 450mm height to match both vehicles. Did I read somewhere that
    there is a max height for coupling mounting?

    I will make the stub axles. I will fit hylux disk hubs (genuine) and brakes. I
    will use sunrasias and off road tyres.
    So many questions, so many issues.
    Without questioning your fabrication abilities, making your own axles from automotive bits and pieces is playing with fire. Not only does the integrity of your welding come into question, but knowing what to weld, when and where, even with it set up in a jig, will determine the axles wheel alignment and subsequent handling, and tyre life. The fact that you're contemplating using the 39mm round beam is already ringing alarm bells for me, and is contradictory to your wanting maximum load capacity.
    Off the shelf axles are available in 2-1/2" and 4" drop, so 80-85mm isn't too much.

    I have a lot of this stuff because my wife bent our old ute like a banana
    around two big redgums about forty feet apart and did not touch the ground in
    between. Bent herself badly too. Nobody has ever told us exactly how many
    broken ribs. Many is all we heard.
    Hope she's recovered/recovering ok.

    I have been thinking about making it a tipper. I have seen plans here similar
    to my idea with the A-Frame pivotting just forward of the front axle (may have
    been single axle). I have a large hydraulic ram and a pump arrangement which is
    driven by a 12v motor. forward to go up, reverse to go down. A mate used it to
    carry 4.5 cu m sawdust. It tipped that with pivot at back edge. To get 45 deg
    on my trailer will mean rear wheels well off the ground. Its just an idea at
    the moment. Any suggestions?

    The suspension as fitted to the caravan was eye to eye rocker with eye hangers
    at front and rear and both sets of shackle plates on the rocker. On the AL-KO
    web site I have just seen an arrangement with the rear spring fittings reversed
    so shackle plates are at the rear of both springs. What are the pros / cons for
    each arrangement? How do you work out exact positioning for hangers? I don't
    want to just assume they were correct to start with. A general question. What
    are thoughts on slipper springs? I don't like them myself and my son had them
    replaced on a tradie trailer because they caused him grief once too often.

    Springs 45mm x 6mm 8 leaf - One end has two leaves wrapped around eye?
    Chassis and A-Frame 75 x 50 x 3 RHS
    Cross beams 50 x 50 x 3 RHS
    Front and rear tailgates removable and will lay down to provide a level surface
    right thru.

    All suggestions appreciated.

    Dean
    Nothing wrong with slipper springs. Less moving parts and maintenance than shackle spring, but for the same spring dimensions, slippers are a little firmer.
    As for the tandem rocker setup, each manufacturer has their own designs, but for me, the fixed point of the spring at the front of each set is the ideal. It means as the suspension moves through its travel, both axles are moving in the same arc. Whereas the suspension with both the shackles on the centre rocker, the axles will move toward each other as they travel in their arc, causing a greater wheel alignment inbalance.

    For setting up shackle springs, unladen, the vertical line through the centre of the rear hanger bolt should be 1 inch rearward of the centre of the rear spring bolt, with the shackles and bolts in place.
    Too many projects, so little time, even less money!
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  3. #3
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    Hi Yonnee,

    The axles are square and will be reinforced as per post. The main reason for using vehicle parts is to save money as I don't have much at the moment.

    The stubs will be machined from 65mm 1045 and press fit into drop plates so that fixes their accuracy.

    I searched the net and asked around and was told that only Ford and Holden style stubs and bearings were available for normal trailer axle sizes. Hilux stub axles are massive. 65mm is just big enough for seals after machining. I was thinking of 25mm plate for drop but not sure at the moment as they worked out bigger than I first thought they would be (83.3mm centres). This allowed the use of hilux disks which I have 2 already and are only $30 each. I have everything else I need for brakes etc except for the lines which I would buy new.

    Thanks for the info on suspension geometry. Makes sense. I am only working on how the caravan was setup and it is fairly old. Regarding slipper springs, if I recall my son had a spring pop out of the socket a few times when going over gutters etc. Maybe was design fault. Trailer was used daily for work as building subby. I think rockers better on tandems to distribute load but have not actually owned one yet. I live on hobby farm and a lot of work with trailer involves rough terrain. Cutting firewood etc.

    I would eventually like to replace suspension, axles etc with new. I would also like electric brakes now that I know how they work. We need a bigger trailer for stock transport now and so cannot wait for finances to catch up. Everything I am using for this rebuild is recycled except for what I have mentioned and the piece of 1045. I have decided to buy new steel for the A - Frame so I am taking note of your advice.

    Dean

  4. #4
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    Hey Dean.
    Just read your Welcome blurb about being a hobby engineer, etc., so I'll figure you don't need me to tell you how lay eggs. Also, I never mean to question the fabricating capabilities of people I've never met, as I'm sure people who don't know me probably take some of my advice with a grain of salt. However, advice is free, mistakes are not.

    There's not a great deal of difference between 39mm round axle material and 40mm square. You stated earlier that you want a fairly high load carrying capacity, so you need to bear in mind that the rated capacity of a 40mm square trailer axle with Holden bearings is around the 1000Kg mark. However, the weak point in this rating is the outer bearing journal, and subsequently, if the same axle is machined with a Falcon outer bearing, it's rated capacity jumps another 100Kg. At this point it's the Inner Holden bearing that becomes the weaker point. So using a stub axle with much bigger bearing journals again, the weaker point will become the axle beam itself, which might not break, but you'll get some pretty mean negative camber.

    From memory, the drop plates that both Melbourne Trailers and Al-Ko use in their 1T - 1.5T drop axles are 40mm thick, 2T drop axles use 50mm drop plates. (And although it's been 10 years since I worked for either of them, I can't see why they would change)

    I too have seen Slipper Spring pop out of their rear hangers, and that's from one of two reasons. Either the spring hanger is attached too far back (there should be 10mm of spring sticking out past the hanger when there is absolutely no load on the spring) or, the trailer is reversed over something, such as a gutter, usually with enough force to get a fully loaded trailer up the gutter...

    As for Tandem configuration, the two biggest differences between Slipper springs and Rocker springs is the load they transfer to the towing vehicle, and the load each axle can carry. Because Slipper springs are independent, as you place a load in the trailer forward of the centre hanger, the front spring set will bear most of this load, but will not transfer any of it to the rear springs, nor much to the towball. This also makes it less critical where the load is placed in the trailer (within reason). With a Rocker spring set, the centre rocker is a pivot point, essentially making the trailer a mobile see-saw, so that any load placed forward of the centre hanger adds weight to the towball, but any load placed behind, reduces it. So this makes it quite critical where the main load is placed in a trailer with load sharing suspension.
    You are correct in saying that the Rocker suspension system distributes the load between the axles, so two 1000Kg axles will carry 2000Kg, whereas you'd need two 1200Kg axles to carry 2000Kg with a Slipper suspension, or any Independent suspension for that matter.
    Too many projects, so little time, even less money!
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  5. #5
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    Yonnee.
    I have been thinking about my reply today and have decided that there is probably too much work involved in fitting temporary axles on a setup such as I described. I will get new axle material when I am ready for that part of the construction if I can afford to. Do the job right now and save redoing it later.

    What would you recommend. 45mm square seems to give a 1500kg axle capacity less 25% because wheels will be 15inch still gives trailer gross of 2250kg. Enough for me. I have read your post regarding reductions for over 14inch wheels. These figures came from trailer wharehouse web site. Is a seperate axle (drop) made from the same grades of steel as stubs. I need to price these.

    2000kg is max for the trailer as I have descibed anyway, unless better brakes are used, as I understand it.

    Sounds like some mean hanger plates. I have two plates 300mm x300mm x 25 mm. I was going to cut in 4 but not big enough then, given drop centre of 83.5mm (Measurement from TurboCad). Add 25mm (half of Axle) and another 25mm for stub only leaves 8mm above stub and below axle. Have to think about that one.

    Reversing over gutters is a common occurance with tradie trailers as often the driveways are already taken. That would probably explain that issue.

    Thanks for the comparison between independant and load sharing suspension. I now see that there are benefits to both and it is best to determine which suits your situation. Any rough situations and I will be using the 4wd so weight is not really an issue on the ball. Besides I already have a load sharing setup.

    On that subject I like the idea of having the fixed point of the spring at the front of each set as you described, but that would mean a different rocker arrangement. I have cast iron rockers which are worn but I would bore out the holes and fit bushes to them. The bolts are ground and hardened and have grease nipples and thru holes. Hard to convert these hangers so would have to make new ones I think. I have just looked at one on trailer wharehouse site. Not as strong/rigid as cast iron I think. Another one to think about.

    As you said So many questions, so many issues.

    Dean

  6. #6
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    Dean.
    I'm not sure whether you misinterpreted anything I've written, or just have a case of information overload, but I've never stated an axle rating reduction based on the size of the wheel rim alone. The trailer industry is a little behind the times when it comes to its recommendations of axle capacities and late model, large diameter passenger car rims with low profile tyres. It comes from the days when passenger cars had 13's & 14's, and 4WD's had 15's & 16's. It's the size and weight of an Off-road wheel and tyre that reduces an axles rated capacity.

    So, a 45mm axle with (Slimline) Falcon bearings has a rating of 1400Kg when running Passenger car wheels & tyres, or 1250Kg with Off-road wheels & tyres. (Not 25%) If this is then fitted to your trailer with load-sharing suspension, then your trailer's axle carrying capacity will be 2500Kg.

    Now, the 2000Kg mark is not a point that requires "better" brakes, but requires a system that can be operated from the driver's seat, and a Break away system that the trailer applies its own brakes for 15 mins should it become detached from the towing vehicle while travelling. This can still utilise hydraulic brakes, just much more expensively.
    Too many projects, so little time, even less money!
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  7. #7
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    Yonnee
    I wasn't implying that this was your position, but that this was what you were discussing with another member. What you just wrote is exactly what I recall. I was saying this situation (reduced capacity for >14inch) is what I have read on web sites ie trailer wharehouse, but I also acknowledge your take on this as somewhat different.

    Regarding brakes I was under the impression that over 2000kg and electric brakes were required. Now I see that this is not exactly correct after looking at the Alko site and your previous post. The end result is that I will aim for a max capacity of 2000kg for my trailer. 45mm Axles will suffice. My word "better" should probably have changed to "More Expensive". I was leaving the in depth brake research until after I worked out the structural parts.

    On the subject of axles have you any knowledge of, or opinions about increasing strength through triangulation as per drawing attached.

    These 40mm and 50mm drop plates you mentioned. What external dimensions was used. ie How much metal extending beyond axle/stub. My thoughts on size as per drawing attached were based on material available.

  8. #8
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    Yonnee
    See if this works now. Should be 4. Split and suspension tipping should have been in first post. The other two in the oops post. What I was doing was using the attachments window to upload thinking that was all that was needed. The oops was because I just happened to click on the attachments icon again to check something and saw the "Insert All" command. I hope everything is now sorted.

    Dean

    Attachment 160064

    Attachment 160065

    Attachment 160066

    Attachment 160067

  9. #9
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    Yonnee is offline Trailer Bloke & Mild Mannered Moderator
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    Quote Originally Posted by Oldneweng View Post
    Yonnee
    I wasn't implying that this was your position, but that this was what you were discussing with another member. What you just wrote is exactly what I recall. I was saying this situation (reduced capacity for >14inch) is what I have read on web sites ie trailer wharehouse, but I also acknowledge your take on this as somewhat different.


    Regarding brakes I was under the impression that over 2000kg and electric brakes were required. Now I see that this is not exactly correct after looking at the Alko site and your previous post. The end result is that I will aim for a max capacity of 2000kg for my trailer. 45mm Axles will suffice. My word "better" should probably have changed to "More Expensive". I was leaving the in depth brake research until after I worked out the structural parts.
    Here's a thing. The 2000Kg limit for brakes on a trailer is its registered loaded weight, however there is nothing to say you can't have an axle and/or suspension capacity greater than this. I would never publically state you could travel on public roads with a trailer loaded over its rated capacity, but a safety margin built into your driveline would not be frowned upon, and in fact, I usually suggest and recommend it.
    Also, interestingly enough, this 2000Kg limit is based on GTM (Gross Trailer Mass), which is the weight of the loaded trailer on it's wheels, while attached to the tow vehicle, rather than ATM (Aggregate Trailer Mass), which is the fully loaded trailer completely detached from the tow vehicle. What this means is that if you have a loaded trailer weighing 2100Kg, loaded so that it had 120Kg ball weight, you'd technically be under the limit for having 4-wheeled brakes and Breakaway.
    However... the braking efficiency of even Electric brakes is reduces over 1600Kg, so only having single axle brakes at 2000Kg is asking for trouble.

    On the subject of axles have you any knowledge of, or opinions about increasing strength through triangulation as per drawing attached.
    Stiffening of an axle as you've drawn is not recommended. The axle, loaded near its capacity does need to flex, so stiffening will reduce that capacity.
    Same goes for the drawbar. With a heavy load, the drawbar can and will flex. If it is stiffened and braced, it will lead to long term failure if consistantly loaded near its maximum.

    These 40mm and 50mm drop plates you mentioned. What external dimensions was used. ie How much metal extending beyond axle/stub. My thoughts on size as per drawing attached were based on material available.
    I'm only going from memory, the drop plates were approximately 100mm wide and 40mm thick. There was around 5mm of the axle beam and stub axle sticking through to allow for a good fillet weld. These were all welded in jigs to keep the stubs aligned, and marked as to which side was welded first so that if the welding did effect the alignment, it had toe-in rather than toe-out. All overlay and drop axles then had a slight positive camber bent into them before assembly of brakes and hubs.
    Too many projects, so little time, even less money!
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  10. #10
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    Yonnee

    Here's a thing. The 2000Kg limit for brakes on a trailer is its registered loaded weight, however there is nothing to say you can't have an axle and/or suspension capacity greater than this. I would never publically state you could travel on public roads with a trailer loaded over its rated capacity, but a safety margin built into your driveline would not be frowned upon, and in fact, I usually suggest and recommend it.
    Also, interestingly enough, this 2000Kg limit is based on GTM (Gross Trailer Mass), which is the weight of the loaded trailer on it's wheels, while attached to the tow vehicle, rather than ATM (Aggregate Trailer Mass), which is the fully loaded trailer completely detached from the tow vehicle. What this means is that if you have a loaded trailer weighing 2100Kg, loaded so that it had 120Kg ball weight, you'd technically be under the limit for having 4-wheeled brakes and Breakaway.
    However... the braking efficiency of even Electric brakes is reduces over 1600Kg, so only having single axle brakes at 2000Kg is asking for trouble.
    Good points. As per one of your previous replies "a 45mm axle with (Slimline) Falcon bearings has a rating of 1400Kg when running Passenger car wheels & tyres, or 1250Kg with Off-road wheels & tyres. (Not 25%) If this is then fitted to your trailer with load-sharing suspension, then your trailer's axle carrying capacity will be 2500Kg." I will be using hilux 4wd bearings which have 50mm and 45mm inside dimensions so I should get at least 2500Kg capacity. I will be fitting brakes on all wheels despite the fact that when talking to a local trailer builder about this he said 4 wheels wouldn't be any better than 2. Doh, why has my car got 4 wheel brakes then? I ignored him.


    Stiffening of an axle as you've drawn is not recommended. The axle, loaded near its capacity does need to flex, so stiffening will reduce that capacity.
    Same goes for the drawbar. With a heavy load, the drawbar can and will flex. If it is stiffened and braced, it will lead to long term failure if consistantly loaded near its maximum.
    Point taken. This is why I am asking these questions. I have a mate who is brilliant at anything to do with engineering such as this but he is very hard to get hold of. He answered straight away to birthday invite (50th) but previously I had 18 month wait for contact. Also more opinions are better. I just borrowed a horse float which I noticed had the draw bar stiffened the same as my drawing.


    I'm only going from memory, the drop plates were approximately 100mm wide and 40mm thick. There was around 5mm of the axle beam and stub axle sticking through to allow for a good fillet weld. These were all welded in jigs to keep the stubs aligned, and marked as to which side was welded first so that if the welding did effect the alignment, it had toe-in rather than toe-out. All overlay and drop axles then had a slight positive camber bent into them before assembly of brakes and hubs.
    I will have press fit for stubs but a bit hard for axles as my press is not quite that tall, not to mention much harder to machine press fit for square and axle is way too long for my lathe. I will make up a jig. I have some 6inch by 5/8 angle that would do.


    What type of steel for axles. Should I use 1045 or similar? Will get some quotes. I am nearly 100km from nearest dedicated steel supplier. The trailer guy may be able to supply as he does sell steel but his prices may a bit high. He is closer and we go that way more often. Cheapest price I got for stub axle steel was from BlueScope at about half of the only other place interested. They suggested BlueScope.

    What are the chances of other suppliers in capital cities being cheaper than BlueScope. I may be able to get the axle material on a trip to Adelaide, or have someone with a big car bring them down. First attempt at quotes with this sytem. Hope this works ok. Next attempt after some FAQ research which showed nothing, then a poke around. It the poke that does it every time.

    Dean

    ps Looks good in preview. Fingers crossed.

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