My expedition hybrid trailer build. (1 Viewer)

[bmw635]

My hybrid expedition trailer build.

Been busy researching, designing, and fabbing my own trailer that's a hybrid of a Conqueror and Coleman.

Here's what we got after 2 weeks of off hour build. Finishing the details on the frame next week then onto box build.

 

[TrekboxX]

Looking great! How did you choose/size the springs and shocks for the projected weight? I'm interested in building a similar suspension setup one day, as well. Keep up the good work!

 

[bmw635]

From weight capacity, desired suspension travel, wheel size, trailer height, I look for springs from cars, trucks that has similar weight , spring rate, coil count to give the ideal set up to match the trailer.

This is my first ever trailer build but I am using basic car suspension design and performance to yield the same desired result. It sounds vague but every trailer weight, intended use, and suspension design from A-arm length to vertical travel to shock and spring type provide the best handling. I am debating on adding a sway bar to improve handling at the expense of weight and travel.

Not sure if that explains it but I'll be happy to give you my thought base on your trail type, trailer weight and size- just let me know what you have in mind and I'll tell you what I know. As you can see in my sig, I built , customized, painted, modified everything on my cars so that's where I learned. Fortunately, everything turn out as planned and calculated so I am pretty happy-saves lots of time redoing things.

Peter

 

[shakotankei]

subscribed!
Suspension looks great. Way better than my super stiff military suspension on my M101CDN.
Looks like you are off to a great start. Keep up the good work Peter!
Any pics/drawings of your box design? Might have to drop by and check it out.

 

[titanpat57]

Great job....all that suspension design is really intriguing...

I have no idea what I'm looking at, but it looks really cool for sure!

Looking forward to the build

 

[bmw635]

subscribed!
Suspension looks great. Way better than my super stiff military suspension on my M101CDN.
Looks like you are off to a great start. Keep up the good work Peter!
Any pics/drawings of your box design? Might have to drop by and check it out.

All I got is a 5" cardboard model for the shop to design and build as I can't even use Sketchup and shop don't have CAD.

Imagine a Conqueror trailer with popup and popout like Coleman, Jayco. Box is 7'L x 5'W x 4'H . Fully expanded can sleep 8-9.

If you want to change out your leaf springs, PM me your trailer length, width, weight and I'll give you rec'd on springs to use as the A-arm design I have can be retrofit to any trailer. Or if you want to swing by the shop by 405 & Westminster to check out the frame and box , you're welcome.

 

[45Kevin]

Looking nice.

It looks as though your shocks need to be more parallel with the direction of swing. ie. more up and down.

 

[ntsqd]

It's a classic problem with trailer frames that have rails too close to the tires (often by necessity) for proper placement and orientation of the dampers. AT has the same problem with their ITS as do the couple of OZ trailers that I've looked at.

For springs I would look at using coil-over springs instead. Can buy them by small increments of a huge range of known spring rates and if you miss and do not cosmetically damage them most vendors will exchange them for a different rate.

About the only thing that bothers me is the tongue. A common on these various off road forums construction method is as you have it, but there will be a very large Moment at the front edge of the front cross-member. You may or may not get away with it, but a heavier trailer built like that will fail the tongue tube at the front cross-member. Tongue tubes not only need to be continuous, they also need to be under the rest of the frame. Better is if there are two tongue tubes in an 'A' shape where the rears of the tubes tie into the side rails where the front spring or suspension anchor points are. I'm guessing that you didn't go down that trail based on being able to jack-knife the trailer into a much sharper turn.

Since trailers do not articulate (no force available to do that) I wouldn't worry too much about the loss of travel that a sway bar brings with it. However since occupant comfort isn't a priority with a trailer, the springs rates don't have to be any softer than one that doesn't break the eggs, foam the beer, or fatigue the structure. Getting into that rate range may negate the need for one.

 

[bmw635]

Looking nice.

It looks as though your shocks need to be more parallel with the direction of swing. ie. more up and down.

Shortest absorber I found fits like that otherwise it's almost horizontal. By the time the box is built, 40 gal water tank, 12 gal gas tank, a spare tire, 60L fridge, 18"x18"x 30" SS kitchen/ counter/ pantry / sink, 2 batteries, etc... It will lower another 2"-3". The suspension travel by then is no more than 4-5".

Thanks for raising issue.

 

[bmw635]

It's a classic problem with trailer frames that have rails too close to the tires (often by necessity) for proper placement and orientation of the dampers. AT has the same problem with their ITS as do the couple of OZ trailers that I've looked at.

For springs I would look at using coil-over springs instead. Can buy them by small increments of a huge range of known spring rates and if you miss and do not cosmetically damage them most vendors will exchange them for a different rate.

About the only thing that bothers me is the tongue. A common on these various off road forums construction method is as you have it, but there will be a very large Moment at the front edge of the front cross-member. You may or may not get away with it, but a heavier trailer built like that will fail the tongue tube at the front cross-member. Tongue tubes not only need to be continuous, they also need to be under the rest of the frame. Better is if there are two tongue tubes in an 'A' shape where the rears of the tubes tie into the side rails where the front spring or suspension anchor points are. I'm guessing that you didn't go down that trail based on being able to jack-knife the trailer into a much sharper turn.

Since trailers do not articulate (no force available to do that) I wouldn't worry too much about the loss of travel that a sway bar brings with it. However since occupant comfort isn't a priority with a trailer, the springs rates don't have to be any softer than one that doesn't break the eggs, foam the beer, or fatigue the structure. Getting into that rate range may negate the need for one.

Track width is matched to the 80= 6ft. I want bottom floor to be 49" between tires so 4x8 would fit. I thought about tire blow out hitting the frame / box but something gotta give.

I looked at coil-over, it's not economical, practical for repair/ replace, or reliability. If the mount breaks, you're stuck. Looked at air bag and airshock/ bag combo too but not economical. I have 2 sets of springs : current set is rated for 1200 lbs, the other is 1700 lbs in case control arm and frame is too close due to heavier than expected.

The frame design is .25" wall tubing, slim profile frame due to height limitation. Frame is 24" above ground, box adds another 4ft = 6ft total ~ FJ80 roof line to reduce drag. Being able to do 80degree turn was another factor for the tongue. Btw, the frame aren't finished in that pic. There are more tubing between the wheels and front / rear frame and a triangular frame on the tongue for the tool box. More pics to come as it's at the sheet metal shop for design and layout then back to the frame shop to paint.

I've seen trailers flipped when too bouncy and I added rear swaybar to my 740 that made huge improvement so the sway bar will definitely minimize trailer rocking while speeding on washboards.

 

[ntsqd]

A lot of people do the tongue that way and get away with it on light trailers. Will not live long under a heavy trailer. Even the 1/4t military trailers have the tongue under the frame. You need section height to increase bending strength at that front cross member. Tubes anywhere else won't do much for the tongue even if they solve other issues. Mass won't help, but geometry will.

Not coil-over shock assemblies, just the springs. Definitely don't want it too softly sprung or yeah, you'll flip it.

 

[bmw635]

A lot of people do the tongue that way and get away with it on light trailers. Will not live long under a heavy trailer. Even the 1/4t military trailers have the tongue under the frame. You need section height to increase bending strength at that front cross member. Tubes anywhere else won't do much for the tongue even if they solve other issues. Mass won't help, but geometry will.

Not coil-over shock assemblies, just the springs. Definitely don't want it too softly sprung or yeah, you'll flip it.

You got a point on the tongue section. I expected the tongue to weight @ 200lbs when loaded so I'll have to see how it will hold up. If need to, we can put a V under it , tying the subframe of the suspension to the mid section of the tongue.

I tried to source custom springs but don't know of a source with 172 lbs /in with 14" unsprung length that's why I used the car springs to see the compression and ride height. Thanks for your input.

 

[rocrunr]

Subscribed! Nice start to the trailer build. I agree that the tongue needs to be stronger. I have been planning a similiar build and keep making changes. I thought about a pop out like the Conqueror has at the front but was wondering what to do when it's soaked with rain which is always here. You would have to fold it wet into the interior of the trailer.To me not ideal.

 

[bmw635]

Subscribed! Nice start to the trailer build. I agree that the tongue needs to be stronger. I have been planning a similiar build and keep making changes. I thought about a pop out like the Conqueror has at the front but was wondering what to do when it's soaked with rain which is always here. You would have to fold it wet into the interior of the trailer.To me not ideal.

The material I plan to use is either vinyl for waterproof but no ventilation or denier nylon for more breathability but still water repellant - no rainfly needed.

 

[rocrunr]

Bmw post a pic of your cardboard model.Interested in what this is going to look like?

 

[ntsqd]

For possible future reference: an Eibach sample from here: http://performance-suspension.eibach.com/motorsport/application_look-up
I input coil-over, 3" OD, 14" long free length, Imperial Measure, and got a chart of p/n's and spring rates. 175lbs/in nets this p/n: 1400.300.0175S Searched on Summit Racing (http://www.summitracing.com/parts/eib-14003000175s) they come up at $106 each.

By now you're probably married to the springs that you've got, but maybe this will help out future readers.

 

[bmw635]

Bmw post a pic of your cardboard model.Interested in what this is going to look like?

Metal shop got the model to figure the bends as I don't want leaks or rattles.

For possible future reference: an Eibach sample from here: http://performance-suspension.eibach.com/motorsport/application_look-up
I input coil-over, 3" OD, 14" long free length, Imperial Measure, and got a chart of p/n's and spring rates. 175lbs/in nets this p/n: 1400.300.0175S Searched on Summit Racing (http://www.summitracing.com/parts/eib-14003000175s) they come up at $106 each.

By now you're probably married to the springs that you've got, but maybe this will help out future readers.

Somehow I got as far as coil-over but nothing clickable beyond here except application lookup that needs yr, model input which doesn't help me. Not sure how you got all the details from the search. May be Ipad problems?

http://performance-suspension.eibach.com/performance_suspension/coil-over/coil-over-springs

The 2 pairs of springs I got is 1200 or 1700 lbs but I can go with other similar range if need to since I got these springs free. Thanks for the Eibach link- may I'll try using PC tomorrow. Thanks.

 

[ntsqd]

My bad, under "Spring Type" I selected "Main". Hopefully that helps, need all of the pull-downs filled in or it gets cranky.

 

[rocrunr]

Any updates ?

 

[rocrunr]

Any thing to update on this great build?