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axle placement ??

Posted:
Mon Apr 09, 2007 1:00 pm
by detsailor
hello from florida, have been thinking of a teardrop for some time, and am almost ready to start the building. i already have a design in mind and after building several small boats i'm sure the project isnt beyond my scope. my biggest question at this time is why is the axle set back so far on the frame instead of more in the middle at the balance point? since i plan on towing this with a VW powered trike tongue weight is a major consideration.

Posted:
Mon Apr 09, 2007 1:13 pm
by rbeemer
Detsailor,
For Teardrops weight is not evenly distributed, since the galley is in the back it contains more weight. Keeping this weight closer to the fulcrum helps maintain trailer balance. If you go to the design library, Andrew has put together an Excel spreadsheet that you can fill in to help determine where your axle should be places and how much tongue weight you can expect. The tongue weight is just to be used to help you estimate tongue weight, actual weight is dependant on how the trailer is loaded.
I am not an engineer by any means this is just my understanding of how it works

Posted:
Mon Apr 09, 2007 4:36 pm
by angib
I can imagine that with a VW trike, you don't want to have too much tongue weight from the trailer, or else the wheelies will start.
You need to have some tongue weight to keep the trailer stable - the higher the tongue weight, the faster the trailer can go before swaying or snaking can start. I have stuck to American recommendations here, which is that the tongue weight should be 10-15% of the total trailer weight - these are loaded/laden figures and how you add the loose gear allows you to adjust this a bit.
With a trike you might want to run a lower hitch weight to avoid upsetting the trike's handling. In Europe, hitch weight percentages as low as 4% are considered reasonable, but it is assumed that the driver will have learnt how to deal with any snaking that may start (eg, no braking, gentle acceleration, allow the steering to damp itself - don't try to clamp the wheel) and also that the towing speeds may be lower.
You might want to aim for a trailer that's fairly light on tongue weight, as it's probably easier to increase the tongue weight by moving things forwards, rather than trying to reduce it. You might want to think about designing into the trailer frame a way to move the axle a bit if you decide you want to permanently increase or reduce the tongue weight.
Andrew

Posted:
Tue Apr 10, 2007 9:45 pm
by detsailor
i have given a bit of thought to a sliding axle, shouldnt be too hard to fabricate something. also i'm thinking of something even smaller than a conventional teardrop, 4x7 with reduced height, a rolling puptent with no facilities, i really need to keep the weight down. thanks for the feedback, jack

Posted:
Wed Apr 11, 2007 6:28 am
by Geron
Det,
I've given this a tremendous amount of thought since your post on April 9th. Axle placement is extremely important. So have applied the best brain power I could summons I would suggest that you place the Axle
UNDERNEATH the trailer. That is for further explanation ON THE BOTTOM of the floor of the trailer. You know, like lying flat on your back under the trailer looking up -- right there.
That's where I placed the axle on my first build and after agonizing over several other options place the axle underneath my second build as will.
Seems to work quite well.
I do hope this is helpful since this is an extremely important decision.
Thoughtfully
Please, don't offer profuse thanks for this suggestion. It's nothing really.
(Oh, btw, angib's "da man" -- listen to him when it comes to engineering and design. )

Posted:
Wed Apr 11, 2007 7:31 am
by Ira
Jack (that's your name, right?), what part of Florida are you in?
You may want to consider building on the Harbor Freight 4 by 4 trailer--and build over the frame 18 inches front and back to give you a "sleeping" length of 7 feet, if you forego the galley.
Also, that frame's real light compared to a 4 by 8, and it's easier to build OUT from the frame than to chop UP a frame. (I think anyway, depending on what you're better skilled at.)
Don't know though how the HF 4 by 4 would weigh up compared to a custom-made 4 by 7 ALUMINUM trailer, or whether you would want to go in that direction anyway because of cost. (The 4 by 4 HF trailer is fairly cheap.)
This can be a fun build to watch and you can definitely build real light, but I would say stick with the 4-foot height anyway. The little bit you're going to save in weight by reducing the height a little ain't gonna be worth the inconvenience, especially if you're real weight-conscious in other areas.
And remember that depending on your profile, it may just be a full 4' high at one point anyway.
There are things you can do at EVERY step to make it real light. Like, most of us put a wood frame (often 2 by 2s) on top of the trailer, and then add our ply floor to the top of that. But you could also just stick the ply right onto the trailer, if you take certain precautions.
Go for it!

Posted:
Wed Apr 11, 2007 6:09 pm
by Jiminsav
Geron wrote:Det,
I've given this a tremendous amount of thought since your post on April 9th. Axle placement is extremely important. So have applied the best brain power I could summons I would suggest that you place the Axle
UNDERNEATH the trailer. That is for further explanation ON THE BOTTOM of the floor of the trailer. You know, like lying flat on your back under the trailer looking up -- right there.
That's where I placed the axle on my first build and after agonizing over several other options place the axle underneath my second build as will.
Seems to work quite well.
I do hope this is helpful since this is an extremely important decision.
Thoughtfully

Please, don't offer profuse thanks for this suggestion. It's nothing really.
(Oh, btw, angib's "da man" -- listen to him when it comes to engineering and design. )
hahahahahahahaha..darn Comedians..when you ask for help, you get hindrance.


Posted:
Thu Apr 12, 2007 2:05 pm
by critter
Hey JIm,
I guess i screwed up again,I put mine on top

then I had to flip it over......

I know 1 in every crowd!