Explorer Build - 5x9

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Explorer Build - 5x9

Postby Maranatha1911 » Sat Jun 30, 2018 4:16 am

Well, here goes nothing.
This is my first post, first design, first self built trailer - you get the idea.

Let me start off by saying - this forum is just absolutely amazing. Big thanks from Germany to all the wonderful people and for the information they're willing to share.

Our trailer will be our new adventure home base for the family upon returning to Colorado. We have 2 kiddos, 7 and almost born.
The objective is to build a trailer that lets us explore the wild places of the West. Anything off grid is right up our alley. Although we are not going to do crazy rock crawling, I don't mind the occasional mining pass across the Continental Divide or similar. With that in mind, I'm hoping to do something to the likes of Hikertrailer's off road version. Their current lead time is 17 months. Since I am blessed with a certain skillset in woodworking, cabinet making etc I thought to myself, why not build one?

Many details are not ironed out yet, like - exterior skin, aluminum, bed liner or FRP?
Galley kitchen is not entirely designed. Unsure if I'd want a ARB type fridge or just good old ice box.

There are some questions I have. Like, what axle system to use. Torsion half axles or Timbren?
Weight currently is about 1200# give or take. So with the offroading in mind, should I go 3500# or go 2000#

You see, plenty of things to clarify.

If you have comments, ideas or questions - feel free. I have learned a lot from this forum and would love to give back what I can.

Oh and, yes, I know, it's not really a teardrop. Just called it so for a lack of a better term. Help me with this one, would ya?

Cheers, Christoph
Attachments
Teardrop - exterior.jpg
Teardrop - exterior.jpg (51.53 KiB) Viewed 1241 times
Teardrop - extruded.jpg
Teardrop - extruded.jpg (57.59 KiB) Viewed 1241 times
Teardrop - extruded 2.jpg
Teardrop - extruded 2.jpg (75.15 KiB) Viewed 1241 times
Last edited by Maranatha1911 on Tue Jul 03, 2018 1:37 am, edited 2 times in total.
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Re: Explorer Build - 5x9

Postby Maranatha1911 » Sat Jun 30, 2018 4:17 am

Here are a few more images.
Attachments
Teardrop - interior 2.jpg
Teardrop - interior 2.jpg (71.46 KiB) Viewed 1240 times
Teardrop - interior.jpg
Teardrop - interior.jpg (77.91 KiB) Viewed 1240 times
Teardrop - exterior 2.jpg
Teardrop - exterior 2.jpg (50.4 KiB) Viewed 1240 times
Last edited by Maranatha1911 on Tue Jul 03, 2018 1:43 am, edited 1 time in total.
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Re: Explorer Build - 5x9

Postby Swan » Sun Jul 01, 2018 7:20 am

looks like a great build idea . you may need to scale down your pics size a little bit, hard to get a grasp for everything when you have to scroll L&R and U&D so much to see it all
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Re: Explorer Build - 5x9

Postby tony.latham » Mon Jul 02, 2018 8:36 pm

I think you should reconsider the lateral frame members. I believe they will be a problem when getting in and out.

A traditional teardrop works for many reasons. One is that you sit down in the door, on the mattress and swing in. It's the same getting out.

:thinking:

T
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Re: Explorer Build - 5x9

Postby Maranatha1911 » Tue Jul 03, 2018 1:34 am

Swan wrote:looks like a great build idea . you may need to scale down your pics size a little bit, hard to get a grasp for everything when you have to scroll L&R and U&D so much to see it all


Fixed that. Thanks for the tip. :D

tony.latham wrote:I think you should reconsider the lateral frame members. I believe they will be a problem when getting in and out.

A traditional teardrop works for many reasons. One is that you sit down in the door, on the mattress and swing in. It's the same getting out.

:thinking:

T


Good thinking. :thumbsup:
In reality they are not a structural part of the frame, rather an addon. Now that you mentioned it, there really is no good reason to have them there.
In the rear I was hoping to add a propane tank and maybe jerry cans. In the front I was adding them for symetry. The architect in me came through.
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Re: Explorer Build - 5x9

Postby Maranatha1911 » Wed Jul 18, 2018 10:36 am

Sideview.jpg
Sideview.jpg (39.52 KiB) Viewed 989 times


Here is a question in regards to weight distribution of the RTT and roof rack.

Should I aim to keep the RTT centered over the axle or move it forward towards the tongue?

My concern is trailer sway due to the weight on the back end with galley, fridge in galley and RTT.
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Re: Explorer Build - 5x9

Postby KCStudly » Fri Jul 20, 2018 11:01 am

If the camper by itself, loaded for travel, has good balance with proper tongue weight you might at first think that balancing the RTT over the axle makes sense.

Then I thought of wind loading. That thing is going to create a bit of drag, and with it being so far away from the axle centerline, it might actually develop a few (tens of?) pounds of torque tending to lighten the tongue.

You can use a wind pressure calculator (clicky) to get an idea of how much force will be applied to the RTT; and then do a leverage ratio comparing the distance from the center of area on the front of the closed tent to the axle hub center, to the ball hitch to get a rough idea of the magnitude. I'd be interested to see or do the math if you have the inputs (height x width of RTT frontal area, height above axle, distance from axle to hitch ball, expected cruising speed).
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Re: Explorer Build - 5x9

Postby Maranatha1911 » Tue Jul 24, 2018 8:40 am

KCStudly wrote:If the camper by itself, loaded for travel, has good balance with proper tongue weight you might at first think that balancing the RTT over the axle makes sense.

Then I thought of wind loading. That thing is going to create a bit of drag, and with it being so far away from the axle centerline, it might actually develop a few (tens of?) pounds of torque tending to lighten the tongue.

You can use a wind pressure calculator (clicky) to get an idea of how much force will be applied to the RTT; and then do a leverage ratio comparing the distance from the center of area on the front of the closed tent to the axle hub center, to the ball hitch to get a rough idea of the magnitude. I'd be interested to see or do the math if you have the inputs (height x width of RTT frontal area, height above axle, distance from axle to hitch ball, expected cruising speed).


Very interesting point you made. I never even thought of the wind pressure and the lightening of the tongue load. With my limited knowledge of physics, I'd say, yeah, that sounds about right.
However, I am not at all mathematically inclined.

The inputs you mentioned are the following.

closed Tent width by height: 56x12 inches
Height above axle (center of closed RTT): 66 inches
Distance from axle to hitch ball: 118 inches
Expected cruising speed: Max. 75mph

At this point I am inclined to move the tent forward, with the risk of increasing tongue weight. Since the static load of the closed tent won't be that much greater, I'm not too worried about it. And in use the whole trailer is on jacks anyway.
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Re: Explorer Build - 5x9

Postby KCStudly » Tue Jul 24, 2018 1:04 pm

Maranatha1911 wrote:The inputs you mentioned are the following.

closed Tent width by height: 56x12 inches
Height above axle (center of closed RTT): 66 inches
Distance from axle to hitch ball: 118 inches
Expected cruising speed: Max. 75mph


So the frontal area of the RTT converts to about 0.4335 m^2
The speed is equal to 33.5 m/s

So using the default air density the calculator spits out 292 N (Newtons). Converting that to lbs.-force we get 65.6 lbs. (I guess we can call this drag?)

Assuming the 66 inch height above the axle is the center of the frontal area, that means there is about 4329.6 in-lbs (360.8 ft-lbs) of torque reaction at the axle.

So because the tongue is a longer lever, the opposing force (the reduction in tongue weight that will maintain equilibrium... since your trailer will not be doing back flips) will be a lesser value, so we divide by the ball distance... and get 36.7 lbs-force tending to reduce the tongue weight.

Now I'm not suggesting that you add 36.7 (call it 40) lbs of static tongue weight, but it does make sense that a RTT could bump a marginally balanced trailer into one that handles poorly due to lightening of the tongue from wind drag.

One could also make an argument that there would be an offsetting addition of down force due to air hitting the front profile, tending to add tongue weight, and they might be correct depending on the TV and camper profiles... so there is that to consider. (My TV is boxy, the front radius on my camper is relatively small, and the roof of my camper is not much higher than the TV, so I would not expect much added down force due to my profile, more of a slip stream I hope, or torque canceling drag and down force.)

I don't remember if you said how much the RRT weighs, but you may want to bias it forward of the axle, perhaps compensating for 1/2 to 1/3 of the 36.7 lbs calculation (i.e. get 18-20 lbs more on the tongue). That would be another calculation, or require using the popular weight balance calculator here on the forums, to determine a target distance to mount it.

Disclaimer: I'm just noodling this out here and don't claim to be an expert, certainly not on your particular build, or in general (though I am a mechanical designer/engineer who is reasonably good at math :D ). The last thing I would want to do is bugger up your trailer design, so please do your own due diligence and don't take my advice as gospel.
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Re: Explorer Build - 5x9

Postby Rhinoman64 » Wed Jul 25, 2018 12:29 pm

I'll second what Tony said. My frame is from an old popup and had lateral outriggers like you drew. My first thought was to leave them and add tread plate for a running board. One day the getting in and out process dawned on me and I tried to do a butt first mock entry (haven't built the box yet). Realized real quickly that the running board idea was not going to work, especially with my short legs. I removed the front ones and left the rear.
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Re: Explorer Build - 5x9

Postby Maranatha1911 » Fri Jul 27, 2018 5:37 am

KCStudly wrote:
Maranatha1911 wrote:The inputs you mentioned are the following.

closed Tent width by height: 56x12 inches
Height above axle (center of closed RTT): 66 inches
Distance from axle to hitch ball: 118 inches
Expected cruising speed: Max. 75mph


So the frontal area of the RTT converts to about 0.4335 m^2
The speed is equal to 33.5 m/s

So using the default air density the calculator spits out 292 N (Newtons). Converting that to lbs.-force we get 65.6 lbs. (I guess we can call this drag?)

Assuming the 66 inch height above the axle is the center of the frontal area, that means there is about 4329.6 in-lbs (360.8 ft-lbs) of torque reaction at the axle.

So because the tongue is a longer lever, the opposing force (the reduction in tongue weight that will maintain equilibrium... since your trailer will not be doing back flips) will be a lesser value, so we divide by the ball distance... and get 36.7 lbs-force tending to reduce the tongue weight.

Now I'm not suggesting that you add 36.7 (call it 40) lbs of static tongue weight, but it does make sense that a RTT could bump a marginally balanced trailer into one that handles poorly due to lightening of the tongue from wind drag.

One could also make an argument that there would be an offsetting addition of down force due to air hitting the front profile, tending to add tongue weight, and they might be correct depending on the TV and camper profiles... so there is that to consider. (My TV is boxy, the front radius on my camper is relatively small, and the roof of my camper is not much higher than the TV, so I would not expect much added down force due to my profile, more of a slip stream I hope, or torque canceling drag and down force.)

I don't remember if you said how much the RRT weighs, but you may want to bias it forward of the axle, perhaps compensating for 1/2 to 1/3 of the 36.7 lbs calculation (i.e. get 18-20 lbs more on the tongue). That would be another calculation, or require using the popular weight balance calculator here on the forums, to determine a target distance to mount it.

Disclaimer: I'm just noodling this out here and don't claim to be an expert, certainly not on your particular build, or in general (though I am a mechanical designer/engineer who is reasonably good at math :D ). The last thing I would want to do is bugger up your trailer design, so please do your own due diligence and don't take my advice as gospel.


Wow! Thank you so much for the input. :applause:

At this point the following stats are a given.

Calculated weight of trailer w/o wheels 1200-1500 lbs.
RTT weight (included in trailer weight) 150lbs

Axle Position 35/65 ratio

Given your calculations, which btw I would never be able to replicate in a million years :frightened:, I am considering moving the tent forward so that it's 1/3 to 2/3 over the axle.
Additionally, I have a pretty heavy tongue box with the 100AH battery (60lbs) in it. At this point I am confident that my tongue weight is in the 100-150lbs range. My TV's tongue rating is around 500lbs.

All that said, I found a way to move doors and windows to accomodate for the changed location of the RTT.

Teardrop (3) Sideview.jpg
Teardrop (3) Sideview.jpg (72.96 KiB) Viewed 698 times



Rhinoman64 wrote:I'll second what Tony said. My frame is from an old popup and had lateral outriggers like you drew. My first thought was to leave them and add tread plate for a running board. One day the getting in and out process dawned on me and I tried to do a butt first mock entry (haven't built the box yet). Realized real quickly that the running board idea was not going to work, especially with my short legs. I removed the front ones and left the rear.


Thanks for sharing your experience. I totally see the validity. The original purpose was exactly that, a running board. This forum comes in handy in so many different ways. :)
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