another axle location question

[jdsackett]

hi all. new guy here. im in the process of building a large tear drop. cabin car??? i guess you would call it??. anyway, its fairly large, 7' x 14'. all aluminum chassis and walls to keep weight down without sacrificing strength. i want to keep the tires just inside of the outside wall, so cutouts in the chassis and walls have to be made. i really dont want to use a straight axle, i have an idea about an independent suspension using a control arm, coilovers and a hairpin. ive built hotrods using it , so it should work on a trailer. anyway, i really have no solid idea what the various galley components, mattress, and just junk in general will weigh. is there any rule of thumb as to where an axle should be according to length?? if i do end up using this idea, moving the axle will be a major hassle, and redesign which i dont want to do if i can avoid it. if i can get close, i think i can balance things close enough by moving contents. anyway, sorry for the long post, but any help would be greatly appreciated. thanks, and best regards, j.d.

[BrwBier]

Check the Hall Of Fame in the upper left corner, scroll down quite a ways till you come to Robs cabincar. This is the person most likely to be of help to you. He built a beautiful cabincar. No one minds long posts but you will be required to pay with pictures, you will hear about this all the time. So ask away, everyone will try to help.
Brwbier

[jdsackett]

ok, thanks a lot. ill give it a look. ill send up some photos when the floor framing is done. maybe some drawings of the suspension as i dont yet have it mounted. thanks again for the heads up. regards, j.d.

[asianflava]

A torsion axle should do it for you. Independent suspension using a rubber spring with built in damping. Bolt it on, and you are done. It might end up weighing less.

[madjack]

I would also recommend a torsion axle for you and if you look in the "Design Library" at the top of this page and click on "Trailer Balance" you will find a spread sheet for determining axle placement...we will be wanting picture also...we just love da pics 'round here
madjack

[angib]

Jd,

Using the phrases 'Cabin Car' and 'axle position' in the same post sets off alarm bells with me, because the original Cabin Car has an unusually high hitch weight, as a result of having its wheels set a long way back - they have to go a long way back, as the bed/settee must fit in front of them.

Here is my trailer balance spreadsheet (you can download it here) with dimensions as close as I can get to an original Cabin Car:



That hitch weight, at 21% of the total, is no problem, providing you have a tow vehicle that can take the 315lb. It is the result of the wheel position, which is only 29% of the body length from the back end. If you want to move the hitch weight down to the middle of the recomended 10-15% band, then the wheels need to go further forward:



This is with the wheels at 40% of the body length from the back end and you certainly don't want them any further forward than this. Something like 35% of the body length from the back of the body is a good first shot - and coincidentally, that seems to be just where Rob put them in his Cabin Car 'replica'.

Building your own suspension seems to be unecessary extra work when using a stock trailer axle doesn't seem to cause other folks any problems - if you want the trailer to ride fairly low, a torsion axle with a horizontal or 'up' start angle will get you real low. If you PM me your email address, I can send you a pdf of a Cabin Car style trailer showing a suitable layout.

Andrew

[jdsackett]

thanks for the input fellas. very good stuff. asianflava, may just go with that. found a place that sells just the torsion part. might pick up a couple and play with that idea. madjack, will post some pix as soon as i get some. materials should be here friday. have to get over to home depot and get some sawzall blades and some plugs for an adapter for my welder. should be a fun weekend. andrew, i sent you a pm with my email. thanks a lot for the offer and info.

the walls and chassis will be made from t6 aluminum, so i think i can do it under 1000 pounds empty. this stuff is very light and very strong. this should really be fun. cant wait for the metal to get here.

thanks again guys, very nice of you to help me out here. best regards, j.d.

[jdsackett]

thanks andrew, got your e-mail...really good stuff, thanks a bunch. confirmed metal will be in tomorrow. gonna be a fun weekend. regards, j.d.

[Muggnz]

Andrew,

Where does "Extra weight 3 from rear - D3" go on the diagram? I cannot see it. Am I going more blind, than I thought? Or ?

thanks
david

[bobhenry]

if i can get close, i think i can balance things close enough by moving contents. anyway, .

I know there are spred sheets and balance programs but I just used the 60 - 40 rule. 60% of the body length ( without tongue) in the front and
40 % in the rear. On a 14' trailer your axle would be approx 8 1/2 foot from the nose of the box. If you check this against the work sheet most fall within inches of the same "Guess"

[angib]

60% of the body length ( without tongue) in the front and 40 % in the rear.

40% of body length from the back is a good general rule.

If you were going to build a heavy galley, 35% might be a better choice to make sure you don't get a light tongue.

Where does "Extra weight 3 from rear - D3" go on the diagram?

Yeah, it says (or used to say?) in the text that the third weight isn't shown - I don't think you'll ever need to use it, but if I hadn't put it in, someone would have needed it......

Each extra weight has a weight in lb and a distance from the back in inches and you just use them as needed. So weight 2 doesn't have to be on the tongue - you might want to carry 1/4 ton of lead in the middle of the cabin and you could use it for that!

Andrew

[Muggnz]

Thanks Andrew.

I think I'll call the third weight The Phantom. As I'll probably need it to balance my calculations, when I make a mistook.

David