axle location questions

[browningbuck]

so i have got to the point where i need to mount the axles on the trailer. I knew how important this was so i built 90%~ of the trailer before ever considering where to mount the axles. SO! im trying to use the spread sheet that everyone will tell me to use(see attached pic). However being this is so important i need a double check on a few things. Raw trailer as it sits with out axles is 625#. the axles weigh 98#. tire and wheels weigh 154# ( the number is correct they are 255/80 E rated tires and alum wheels). i am installing a solar panel per extra weight number 1 and guess on the extra weight of weight 2 for water battery and a few little things but i think its close.

My first question is: Does the cell for weight of axle/suspension include tire and wheel weight (sounds stupid as i think it should, but due to its location and being considered as "unsprung weight" this is pretty important as it can swing the tongue weight 32# ) i put the weight of everything in the cell currently.

My second question depends on the answer above: Did i fill everything out correctly and the axle center line should be 28" from the back? Please dont just answer to answer, i need experienced advice since i only want to drill the holes through the aluminum once.

My third question is : does any one have suggestions/thought/ideas/or lessons learned that i should take into account at this time? now is the best moment for me to consider anything any one has to say.

[browningbuck]

here is what the trailer will look like with the axle at 28" from the rear (i consider the rear the imaginary line from back of the galley down as shown in the pic as a single line) also see that the cabinets of the bed and the galley are directly over the axle currently. so i would say the live load of the trailer (things not bolted or welded on) wouldnt disturb the tongue % much. however it does lack some aesthetics in the current location (wish it was closer to the tongue) Thoughts/comments are welcomed.

[grantstew8]

My general observation are that the tongue weight in the US is not as critical in the uk so it appears that the axel can be positioned nearer the rear of the trailer. Here, In general terms, it's limited to 75kg about 165 lb nose weight. Our tv are smaller by comparison.

From a techie point of view it makes sense to put most of the td load onto the td axel rather than onto the rear axel if the tv. It should help with economy and handling. Having said all that, a negative nose weight is asking for trouble.

I've got myself in hot water about the differences between us and uk regs on trailers so bear in mind I'm not an expert.

[mikeschn]

A general rule of thumb is to start with the axle location at 34.5" from the rear of the trailer for an 8' trailer, and add 6" for each foot of trailer length.

I think you are too far rearward. With your trailer being almost 10' long, you probably want to be closer to 46.5" from the rear.

Mike...

[angib]

Yes, include wheel weights in the axle/suspension weight.

You are proposing to put nearly 20% of the weight of a trailer right at the back end, So I am not surprised you are getting a more-rearward axle location than normal.

But you seem to have corrupted the spreadsheet - you should only change the contents of the red cells. If you look at the item "Body weight (total - tongue - axle)", you are showing 66.3% which is not 100% - 5% - 12%. I suggest you download a new copy of the spreadsheet and put your numbers in that.

I have done that (see below) and am getting a reasonable 15% tongue weight with the axle at 34", which is some way further back than the 44" that Mike's rule of thumb suggests - but then you are planning to put lots of weight in the galley of an otherwise fairly light trailer.

browningbuck-balance.JPG (117.75 KiB) Viewed 935 times

[browningbuck]

Angib, thank you for the comment! That helps a lot as I was trying to get the tongue at 15% and felt like something was wrong with the numbers I was getting.

you commented that this was a fairly light trailer, i feel as if i WAY over engineered it and built it too heavy. i thought the standard tear was about 1000# or lighter. i was wanting to build another in next winter and sell this one and attempt to engineer to the 800#~ range on the next one.



i think i figured out that i needed to calculate the % of weight my axles are to the total weight of the trailer and needed to change it from 12% to 31%

but im still confused by weight of tongue. I can calculate if i need to the weight of the 3 lengths of 3"X3"X1/4" alum that is in front of the cab of the trailer and use that to change the percent. Im just unclear what number its really asking for.

[pbecker83]

Hello TNTT, first post. I am just thinking out of the box here but couldn't you just drop the trailer on a set of vehicle jack stands to find the balance of the trailer? For example I have 4 jack stands, two I raise higher. The shorter ones go under the tongue and the rear of the trailer. Then start out 36" from the back with the side jacks. You simply keep adjusting the side jacks forward or backwards until the trailer balances itself. You could even put a scale under the jack thats located under the tongue to tell you what the tongue weight is. Thoughts? You wouldn't even need to use jack stands. Maybe just one or two 2x4's across? What should the tongue weight be?

Patrick

[browningbuck]

Hello TNTT, first post. I am just thinking out of the box here but couldn't you just drop the trailer on a set of vehicle jack stands to find the balance of the trailer? For example I have 4 jack stands, two I raise higher. The shorter ones go under the tongue and the rear of the trailer. Then start out 36" from the back with the side jacks. You simply keep adjusting the side jacks forward or backwards until the trailer balances itself. You could even put a scale under the jack thats located under the tongue to tell you what the tongue weight is. Thoughts? You wouldn't even need to use jack stands. Maybe just one or two 2x4's across? What should the tongue weight be?

Patrick

pattrick,
i know fairly close where the current balance point is on this build, however whats important right now as the axles arent mounted is setting it up so the trailer when empty has 15% of the total weight of the trailer and everything in it to be on the tongue. Then with the trailer is loaded (most the weight unfortunately goes in the back reducing my tongue weight) i have to insure not going any less than 9% of the total weight on the tongue. moving my axle back 2" allows me to add about an extra 200# of weight to the trailer with out having any risk driving down the road. However i have reconsidered my current design as there are two small side doors under the galley that i need to be able to swing with out hitting the back of the tire/fenders. So what i think i will do is move the battery i was going to install under the galley to the front into a battery box. this cantilever effect will allow me to center the axle where i originally designed to go (44" form the back right between a big cross member). as well as increase the load i can store in the back. its not as clean looking as i would have liked, but then again not a lot of it has gone as clean as id have liked. But i guess thats what happens on ones first build.

first shows calcs with battery at front with 44" to axles with max load in the rear of 180#
second attach shows calcs with battery at front with 44" to axels with an EMPTY trailer giving me ~14% tongue
third attach shows the trailer with the 44" axle from rear.


I know that many may think im over thinking this as 180# is quite a bit of gear, however what im looking at is really a simple weight of water per gallon as this is where ill be storing my water and that means i can have about 40# of gear (normal for me) and max of 17.5 gallons (thats a pretty decent amount of water).

[mikeschn]

That 44" wheel placement looks much better!

Mike...