axle placement

[johnwgorman]

Sorry for the dumb question. But.... I was looking at the website and found a cool article about how to calculate placement of the axle for best balancing. I closed it out and then tried to find it later and couldn't. Any clues on where to click for this. Again... sorry .

[madjack]

...is this it... http://www.angib.pwp.blueyonder.co.uk/t ... tear81.htm ......................

[johnwgorman]

I shook my head then realized that I could look in the history!!!! Found it there and bookmarked for future senior moment.
Next time I'll use the explosives.
Thx

[Shadow Catcher]

One suggestion, wait for permanent axle placement until you have finished and know the actual balance.

[bobhenry]

I have used the very unscietific 60 / 40 rule. Placing 60% of the BODY
length (body only not including the tongue) in front of the axle and 40% to the rear.

ie a tiny trailer 10 foot (120") nose to tail has 72 inches in front of the axle and 48 to the rear.

With an extremely heavy galley 65 / 35 is perhaps even better. When the results are placed side by side with Andrews balance sheet there is very minor difference.

[eamarquardt]

One suggestion, wait for permanent axle placement until you have finished and know the actual balance.

All spreadsheets, forumlas, etc fall under the category of "swag"s. Easy to weld your suspension to a piece of angle iron or flat bar, build your trailer and load it for bear, then place the suspension where it needs to be to get the balance you desire. I prefer a toungue weight as high as your tow vehicle will allow. Your trailer will ride better and will track better the further back your axle is located.

Has worked for three trailers I've built to date.

See album for pic of springs mounted to angle iron and then mounted on trailer.

Cheers,

Gus

[chamal]

I have read quite a lot of posts regarding axle position and weight distribution, including one or two mind boggling formulae.I'm still confused.

Do the rules of 60% ahead and 40% behind the wheels apply to caravans where the galley is at the front, drawer units/wardrobe in the middle and bed at the end? or is it only applicable to Teardrops where the main weight is in the galley?
It would appear that placing the wheels in the right position in relation to the body is critical to within 2 - 4" to avoid fishtailing/sway.

I'm designing my caravan at present and therefore I don't know the weight of anything so far, however I do have to start somewhere and I intend to use a chassisless tortion box idea, but as I will have wheel cut-outs in the floor, the position of the wheel centres is critical, it will be a 5' x 10' body.

The design with similar proportions in the "Design Library" is the Wanderer 10' and the wheels appear to be 4'6" from the rear of the body to wheel centre.

Do I have to find out the weight of the floor,walls, roof, bed, drawers, wardrobe etc, before I can decide where to put the wheels?
I'm still reading through Angibs super informative posts, but it takes time to sink in, a joiner I am, an engineer I'm not.

Thanks for any advice, I haven't found a forum in the UK with so much experience and help.

regards Alan

[angib]

You won't go far wrong with 60/40, but two things make me think you might want to use 55/45:
- when you say 'caravan', I'm hearing something larger than a teardrop;
- it sounds like you are in the UK, so be aware that European trailers have less tongue weight.

While 10-15% of trailer weight is recommended in the US, no-one in Europe tows with that much tongue weight and 4-7% is more typical. That's one of the reasons why we tow trailers more slowly, but the other factor is that we tow much heavier trailers with the same tow vehicle, so 10-15% of a heavier trailer is too much tongue weight for most tow vehicles.

[chamal]

Thanks Angib,

You're right I live in the beautiful Peak District.
I am designing a typical "Caravan", I know there are plenty of small ones about, but even the Eriba Puck is too heavy for my 2CV ( 596Kg ).
I love teardrops, they're so cute, I've seen some wonderful designs and ideas on this very helpful forum.
However with the British climate I don't want to stand behind the unit to cook etc and I'm too old for canvas.
So I'm designing a small, low, very light unit, my drawings are changing daily as I learn more and see other ideas.

I am designing a monocoque unit to disperse of the heavy chassis altogether and to keep the extremities close to the dimensions of the car.
I have placed half axle "flexiride" suspension and wheels within the unit, so the position of the wheel cut-outs in the floor is my starting point.
If I get the wheel position wrong in the first place, I will only encounter problems later or even ruin the caravan altogether making it un-towable.

As I mentioned the only ones similar are the "Wanderer 10' " and the " Compact 3 ". so I'm looking at 350Kg or LESS, a 5' x 10' pop top with a 3' - 3'3" tongue.
With a 4 - 7% tongue weight that would be eeerrrmmmm, very light, so it would appear weight distribution is critical, front to back and side to side.

Heavy items like gas bottles,fridge, hob,spare wheel, battery etc will alter things a lot it would seem. Air con may be a tad heavy and excessive given we only get 4 HOT days a year here.

So I wonder if others calculate the weight of everything, walls, floor, roof etc. before they put saw to timber.

I offer my thanks in anticipation of any advice given.

Kind regards Alan

[48Rob]

Hi Alan,

I think a lot here on the forum that are building a typical teardrop do not.
Since most are pretty much the same with regard to general size and configuration, weight and balance issues all fall into a narrow range that can be adjusted with cargo redistribution if a little off.

For a travel trailer however, if you don't take the time and effort to understand how weight placement/distribution side to side and front to rear, as it relates to axle placement and balance will affect the towed stability, or copy another trailer with the engineering already proven, you run a high risk of failure.
I would suggest also building a cardboard scale model to help with window and door placement, as well as a full scale interior mockup to be sure everything you want or have designed will work with each other.
What you propose, designing and building a trailer, is a very enjoyable hobby, but one that requires much thought and many calculations.




Rob

[angib]

To tow with a 2CV, you do not want to have 'too much' tongue weight - that soft Citroen suspension will be just dragging on the ground and you will be looking through the fresh air vents under the screen to see the road ahead!

So I would go with 55/45 axle position and take care to get any heavy weights just in front of the axle. You will probably put the heavy gas bottle(s) in a locker at the front, so not very close to the axle, but good enough. You do not want to be adding weights to the front and back of the trailer in the hope of balancing each other out - that will give you a misleadingly 'correct' tongue weight but may still give sway problems.

Once built you will be able to adjust the trailer balance by how it's loaded with loose gear - you might even end up moving something heavy but movable (eg, the battery) to get the right balance.