axle mounting question

[BrwBier]

When in the build do you mount the axle. Early and place it for the right look or later in the build and place it for weight distribution? Does a few inches front to back make much of a difference? Or is it more like 5"to6" the amount needed for much tongue weight difference?
Thanks
Brwbier

[madjack]

...just my take...draw up your profile with all added items indicated anc place for looks and so that the majority of items are over or behind axle...I placed ours based on looks and 20+ years of loading/balancing loads onna 18 wheeler...a couple of inches does make a difference in tongue weight...6"s is starting to make a significant diff in weights...all depending on design and loading...keep in mind that you are not dealing with a lotta weight so that a 20# shift can represent a 20/25% weight shift(on the tongue)
madjack

P.S. Andrew has a pretty good spread sheet in his Design Library(at topof page) for determining tongue weight vs axle placement...

[angib]

Does a few inches front to back make much of a difference? Or is it more like 5"to6" the amount needed for much tongue weight difference?

An inch or two is not very important - how you put loads into the trailer (eg, a cooler in the galley or in the cabin) will affect the balance more than that.

As an example, I was looking at a trailer balance a day or two ago and to change from about 15% hitch weight to about 10% hitch weight required the axle to be moved 8" on a 9' trailer.

So we could say you need to get your axle in the right 6" segment of the trailer, and not worry about getting the right 1-2".

Andrew

[Arne]

This question has bugged me for months. My plan is to build the frame and box and attach the axle stub frames with 1/4" bolts, 1 front, one back on each side. The suspension stub frame will not be attached to the tongue frame.

AFter it is all done, I will move the suspension stub frames to their proper location and mount them securely, and will add fenders.

I know there are places here to plug in numbers, but frankly, I don't know what all the different items will weigh.

[asianflava]

Me too, I checked out the spread sheet but I didn't know what weights to input. I didn't have a trailer yet so how woukd I know. I ended up building the body on the floor of the garage then building the frame to fit it. Doing it this had a few advantages for me.

1. The floor of my garage is relatively flat, which insured the body was
2. With no tongue sticking out, there was much more room to work
3. I was able to get definite measurements for ordering the axle
4. It allowed me to see how much clearance I had between the fender and door

When all was said and done, I ended up putting the axle where it looked best.

[angib]

I know there are places here to plug in numbers, but frankly, I don't know what all the different items will weigh.

I understand this. But there is no easy answer, as whether the galley will be heavy or light makes a big difference. You've seen the photos - some folks have a empty shelf back there and other folks have galleys that are as well-equipped and stocked as my home.

Maybe the answer is to go back to a simple rule (was it 36" from the back on a 8-footer and half any extra length?), but to have two different rules for light and heavy galleys.

Andrew

[Steve_Cox]

I too agonized over where to put the axle, read the posts, did the math and in the end put it where it was esthetically pleasing to my eye before putting any wood on the frame. The TD frame is 114", axle center is at 40" from the rear, the tongue is 39" long. With a 9 gallon water tank, stove and battery in the back and a full 20# propane tank on the tongue, I've got 16% of the weight on the hitch, total weight 1125#. Took it on a test run and did some quick lane changes the TD trailed steady. Quick stops, I detected a slight rise of the tongue and hitch. Guess I got lucky.

[SpeedWagon]

Hello
If you use the side mount torsion axle, they come with a bracket that you weld to the trailer frame, and then the axle bolts to the bracket.
If you tack weld the bracket to the frame in a few places, you only have can grind off small areas of the weld, to move the bracket, and adjust for weight distribution. Weld the bracket on completely when you like the location, and before you mount the fenders.
Dave

[alaska teardrop]

Brew - I agree with the suggestions above that a few inches can make all the differance in finding a proper balance. Some builders (including myself) have found a way to complete the trailer, find the balance point, bolt on the axle and then install the fenders. This, of course, requires some idea of where the weight and door of your trailer will be located.

In reveiwing your album, my concern would be that when the stub axles are attached to the mounting plates the side rail angles will twist causing negative camber.

You might consider adding another cross member in that area and at the same time extending the front to back axle mounting plate to give those few inches of choice when it comes time to make the final balance.

While knowing that my solution does not apply directly to your situation, it may give you some ideas. Fred

[An Ol Timer]

I'd like to bring up a couple of points about trailer weight and balance (W &B) and axle placement. First of all you can worry about the W & B thing if you are into the aesthetics of bigger wheels, different axles and their placement or where you want your doors placed, but the average new teardropper can just go with the purchased trailer as bought. It was designed to carry it's gross when properly positioned and therefore if you build and LOAD your teardrop properly it will do just fine.

I'm surprised that some of the pilots on the forum haven't already discussed the W & B theories as related to teardrops. First just because you setup your tear during construction and use a W & B formula it doesn't mean much after that.

An aircraft is designed and built using the formula to maintain a center of gravity. The center moves fore and aft, but has to stay within a small envelope for the craft to be flyable. (forget any fly-by-wire, etc) After the initial design is accepted, and the craft is built, then the whole thing is set. Now at any future time that any additional equipment is added to the craft a new W & B has to be done.

Now each time that you fly the craft it has to have another W & B done for each passenger and anything else brought aboard.

With your tear it will have a W & B deciding on where you placed it's axle and how you distributed the weight as you built it. Now it needs to be reevaluated as you place permanent things aboard it such as TVs, microwaves, etc. Now it's finally done.

Then you're gonna go camping so you start loading it with water, ice chests loaded with drinks and ice, clothing, etc. These should be placed to maintain your center of balance or in case of a tear your tongue weight.

Now if all this seems too much, your not alone, and if you're into building a tear for fun and camping, then don't worry about all this crap, just build it. Keep it below gross weight and shuffle things around to maintain a decent tongue weight.

[Chip]

My way of trying to get it right was to build the frame and the box seperately and using the 60/40 rule of thumb,, I allowed about 10" of room to slide the box forward or back to get it balanced wher I thought it should be,,,,,The result is unloaded I have a light tongue but it towes fine,,, loaded with "stuff" in the cabin and on the tongue, the weight perportions are just about on the money,,just the way I did it and I lucked out on the location of the axle,,

chipper

[cracker39]

I know that I posted this at least 4 or 5 times before...sorry.

Since I would have sides extending down the outside of the frame, welding the torsion axle mounts on after putting on the sides might burn the wood, so I placed my trailer sides, and other parts and materials on the chassis and floor where they would be installed later, then weighed the sides and tongue, moving the scale position until I had an approximate balance of 88%/12%. It may not be perfect, but I thought it would be close, and that I could load the TTT to adjust the balance if it's off too much. Then, I welded on the mounts that the axle would be bolted to.

With the trailer almost done, the battery is in place onthe tongue and the galley cabinet started. I still have to put the rear cabinetry in and put the A/C unit in back, so the front is a little heavier right now than it will be when the TTT is finished At the moment, the tongue weight is 160 lbs, and I'm estimating the finished dry weight at between 1250 and 1350. So, it looks like I'm in the ball park for the correct balance between 10% to 15% for the tongue weight. I have a feeling that it will be pretty close to the 12% I was shooting for.