Where to put wheels?
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This is not a SU specific topic, but I'm hoping someone with an engineering background might also be a SU user.
I'm trying to design a camper/trailer and have no idea how to determine the correct placement for the wheels/axle. Is it at the point of balance (is this the fulcrum point?) or somewhere else? Is there an easy way to geometrically find the correct position or is the whole thing far more complex than some basic geometry? I'm hoping not.
My apologies if this question if too far off topic to warrant discussion, but if it helps, I am using SU to design the thing.
If all else fails, I can always go off some design plans (if i can find any) and design the camper to match a known chassis design, but it would be nice to know how to do it.
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I m not an engineer but thinking straight and watching the actual trailers ,the wheels should be placed in the rear half to allow the trailer to weight more on the towbar for not rolling back when is unhooked and for not changing the stability of the car by changing the weight distribution of the tractor car(u can load the car with some weight and there will be no problem with stability ,but if u have more weight on the trailer size the back of the tractor car will dance like on ice ).
In other words u must put the axis in such way that the trailer will stand on the towbar( i think ,
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You should calculate the location of the CG of the trailer and position the wheels so that 10-15% of the trailer's weight is on the tongue. As to where the wheels end up, it'll depend upon the trailer.
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@dave r said:
You should calculate the location of the CG of the trailer and position the wheels so that 10-15% of the trailer's weight is on the tongue. As to where the wheels end up, it'll depend upon the trailer.
What you say makes perfect sense however not being an engineer myself I have no idea how to :-
(1)Calculate the CG (assume that's Center of Gravity) and
(2)Calculate if 10-15% of the trailer's weight is on the tongue.Good answer tho
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Baffle 'em with BS.
Calculating the CG (yes, Center of Gravity) could be a bit of a challenge depending upon the trailer. It depends upon how you arrange things and what you stuff in there. How big of a camper is this that you are designing? And what sort of accommodations will it have?
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@dave r said:
Baffle 'em with BS.
How big of a camper is this that you are designing? And what sort of accommodations will it have?It's commonly called a Teardrop Camper - little more than a bed with a roof and a kitchenette type facility tucked away in the back end under a hinged lid.
Some examples:
http://sketchup.google.com/3dwarehouse/details?mid=efcc22862987cdd57d6543d84affccd9&prevstart=84
http://sketchup.google.com/3dwarehouse/details?mid=11f01d9424bdd8ea9f3f9e8d9432a9f4&ct=mdrm&prevstart=84 -
TIG has a Center of gravity plugin although of course it may not be as straightforward as it first seems since there may be different (real world) materials used, the load changes many things etc.
(I am not an engineer myself)
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@gaieus said:
TIG has a Center of gravity plugin although of course it may not be as straightforward as it first seems since there may be different (real world) materials used, the load changes many things etc.
(I am not an engineer myself)
This is GREAT! - but the more I think about it, it's going to be a lot more complicated given the many real-world variables. I have no idea what the final structure would weigh or where the load is distributed etc etc. This further implies that placing the axle correctly can really only be done after the thing is build and sitting on the chassis.
Having said all that - it can still be used to draw something that will at least look reasonable.
Thank you for finding this plug!
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I love the little tear drop trailers. It sounds like a fun project.
I do agree that the actual axle location should be determined after the trailer is essentially complete. The trailer I had for the sailboat I built was designed so the axle could be moved forward and aft to adjust the tongue weight. You could make a similar arrangement. In general, I would imagine you'll end up with the axle somewhere slightly behind the center of the length of the trailer not including the tongue.
Some folks build these little teardrops on manufactured utility trailers and I've wondered how they work out for towing. Perhaps they are very good. You might take a look at some and perhaps measure them to get an idea.
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@dave r said:
Some folks build these little teardrops on manufactured utility trailers and I've wondered how they work out for towing.
Yeah, they're great (perfect as a weekender getaway unit) and (apparently) easy to make. My original idea was to do just that - build a box to fit into a standard manufactured utility trailer in a slide on/off approach. But - I then had the same thought as you regarding the load distribution's effect on towing and decided that building from scratch might prove a better option as well as avoiding a number of other design factors resulting from a combo approach.
I've always wanted to build one and now with SU I can mess around with all sorts of crazy ideas without spending any money and if it turns out cool, I might take it to the next level and build a real one (or sell the design/s). Building (designing) it in SU is just a ton of fun and offers so much freedom to try different things before picking up tools and spending a fortune on materials. It also helps (me) learn SU netter if I have an actual project to work on.
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It certainly is good to have something you are really interested in as a subject for learning SketchUp. I taught a fellow who wanted to draw the Welsh stick chairs he makes. Kind of a big bite to chew for a first model but he was interested and it helped him stick with it.
I hope you build one and will share the photos with us. Or at least with me.
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@dave r said:
I hope you build one and will share the photos with us. Or at least with me.
LOL! - I'm the worlds worst procrastinator. Don't hold your breath. However I might actually manage to build a SU version which you're welcome to.
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Thank you. I guess I'll settle for that.
You certainly can't be worse than I am. I have wood in my shop that has petrified before I could get round to using it.
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