16 foot single wheel unusual TD build

[KCStudly]

I'll say it again. I'm not opposed to the single wheel idea. It may not seem like it, but I am truly trying to help. To be successful, you (the proverbial "you" including me) have to understand the goal, any special conditions that need to be addressed (which means playing devils advocate), and the practicality (cost in time and materials, plus anticipate performance to goal). This is, in a nut shell, "the" engineering process. Some of the best and worst engineering decisions have been made based on passion alone.

All I see in this thread is people trying to help provide input to the process. No need to take personal offense. Stick around a while, get to know us, and you will see that we are an inventive bunch with lots of good ideas and a willingness to help each other.

Share more details. As you work thru the process you will get much advice. Until we get to know you and your capabilities, we may make suggestions that you have already considered, and you may be more well informed than we are. Then again, maybe not, so be careful that your passion doesn't make you blind to good advice. It works both ways. That's the beauty of this forum.

[WeirdDogGuy]

???????

I'm not offended at all! I'm grateful to anyone who takes time out of their busy day to reply to one of my threads. However, I AM hideously busy so some of my replies may be curt but that has nothing to do with you or anyone else who is replying. Just busy-don't read anything into it.

[mezmo]

Hi again WeirdDogGuy,

I was just wondering, as I don't recall it being mentioned, but how are
you going to load your equipment into the trailer ? Before hitching up?
And can loading be done with the tow-vee hitched to the trailer ? And how
close together will the tow-vee and trailer be when hitched up ? Are you
going for a very close distance to help keep in the tow-vee's airflow ? or
are you having enough tongue length to let you do a 90degree jack-knife?
Just curious.

Also, how are you going to support the front of the trailer when it is not
hitched to the tow-vee ? A couple of tongue type screw jacks ?

BTW:
Here's a link to a Hemmings Blog post on the Bowlus Papoose Protoype
that was just recently sold at auction. The first pic illustrates what I was
talking about when I said two [small as shown] wheels could be tucked
in behind the body taper. Your design, to me, resembles a "chopped" and
"stretched" Papoose ! Eh ? http://blog.hemmings.com/index.php/2014 ... the-block/

I get that you want to do it with one wheel, but a backup plan can't hurt either
if that won't work as you envision.

Cheers,
Norm/mezmo

[rowerwet]

This is developing into the most common criticism; that one wheel is wrong. If 2 wheels are better than 1, then wouldn't 10 wheels be better than 2 ?????

simple geometry is why, two points in space determine a line, a line is not stable in the cross wise axis, three points determine a plane, a plane is very stable. three points also make a triangle, a triangle is very stable (it is the strongest shape to build with as it can't deform without crushing or tearing)
a trailer has two wheels and a hitch, those three points make it into a triangle for support, with the weight concentrated over the two aft points (axle) three points keep it from rolling and pitching unless extreme force is applied.
any more wheels after two are just to help carry the load, your already have enough support for the load so no more tires are needed once stability is established.
your design uses the rear wheels of the car as the two points of the triangle for the trailer, we all are concerned that the torque will take out the weakest link, (the U joint) since unlike a normal lay out, your load is concentrated on one point of the triangle, instead of centered over two points of it.

[WeirdDogGuy]

Hi again WeirdDogGuy,

I was just wondering, as I don't recall it being mentioned, but how are
you going to load your equipment into the trailer ?

I am still stewing on this. The windsurfer and the kayak can fit thru the front door no problem. But I don't think that I want to keep dragging a muddy mountain bike in and out of the trailer. I ride a lot and it would be a mess. So, I'm thinking of having a back room that is accessed by a side door near the rear of the trailer, where the little triangular window is. It would just be a little room for my mbike and a port-a-pottie. I could make the room divider wall out of veneered foam and it would stiffen up my structure. I have the room to do this but I'm not crazy about the aero drag that I would get from the door break and hinges. I do have a beautiful set of chrome hinges from a 1967 Volvo station wagon that look nice but I haven't weighed them yet. It's probably going to happen. I'll draw it in cad and post a pix eventually

Before itching up?
And can loading be done with the tow-vee hitched to the trailer ?

Yes,either

And how
close together will the tow-vee and trailer be when hitched up ? Are you
going for a very close distance to help keep in the tow-vee's airflow ? or
are you having enough tongue length to let you do a 90degree jack-knife

Right now, I'm at 29 inches but I haven't welded the u joint in yet and that will add at least another 8 inches. It's tempting to want the trailer right up against the TV so it drafts well but I have a front door on the trailer and it swings out. Also, my Soob hatch swings up, just like a "normal" teardrop hatch, so my Soob hatch must clear the trailer when I open it. Of course, I can make my spine telescopic. If I nest a 2nd piece of square tubing inside my spine, I can pull the trailer right up against the TV (within reason-still need turning clearances) and then pull a bolt (or 2)
and extend it when I'm parked. It would not be hard to do, just not sure yet if I'm going to do it. I've been parking my Soob next to the garage with the hatch up to get a feeling for clearances so if I have a solid spine, I'll just do what feels best spacially. That's my cooking area (kitchenette in back of Soob under hatch) so I should be comfortable. If I use a telescopic spine, then it doesn't matter since I can adjust the length.

Also, how are you going to support the front of the trailer when it is not
hitched to the tow-vee ? A couple of tongue type screw jacks ?

One swing-down jack in each corner. I haven't bought them yet but I'm leaning towards the jacks that swing down and then you jack them a click or 2 like an old fashioned bumper jack. When it is not attached to the TV, it will be attached to the earth (thru gravity) like a normal tear ie 3 points.

Thx. Andy

[WeirdDogGuy]

Your design, to me, resembles a "chopped" and
"stretched" Papoose ! Eh ? http://blog.hemmings.com/index.php/2014 ... the-block/

I get that you want to do it with one wheel, but a backup plan can't hurt either
if that won't work as you envision.

Cheers,
Norm/mezmo

I'll take that as a great compliment. I like the lines on that Papoose.

[WeirdDogGuy]

This is developing into the most common criticism; that one wheel is wrong. If 2 wheels are better than 1, then wouldn't 10 wheels be better than 2 ?????

your design uses the rear wheels of the car as the two points of the triangle for the trailer, we all are concerned that the torque will take out the weakest link, (the U joint) since unlike a normal lay out, your load is concentrated on one point of the triangle, instead of centered over two points of it.

Yes and no. You are contradicting yourself here. My design does use the rear wheels of the car as two points of support, I can agree with that, but it does not concentrate all my load on one point. Let's just say the weight distribution on the trailer is even (it's not). Then half the load would exit out the back single wheel and half would be loaded out through the rear of the TV. If all the load was on the trailer rear wheel, then when I detached from the TV, the hitch would float magically in the air.

And I don't believe the u joint is the weak link but I could be wrong. I'll know once my weights start coming in. I will be surprised if that is the case.

Thx for your ideas. Andy

[mezmo]

Hi WeirdDogGuy/Andy,

I got to thinking some more on your described hitching set-up and
decided to Google Image "single-wheel motorcycle trailers" to see if I
could see anything...

I ran into some interesting results that I thought that all those who are
wondering how it will work may be interested in seeing, and maybe there
may even be some 'new-to-you' info for your use.

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INFO FROM:

Here are some links for a 2axis U-joint [action] hitch examples:
http://www.advrider.com/forums/showthre ... 827&page=2 [The link
worked initially, but didn't on a recheck, maybe it will work later.] See the
vortexau 02-03-12 08:51PM Post.

There is a U.S. Company that makes single-wheel motor cycle trailers and the 2axis
U-Joint action hitch and receiver:
http://www.uni-go.com
http://www.uni-go.com/categories.php
Example of their Drawbar/Hitch:
http://www.uni-go.com/proddetail.php?prod=T3260
Example of their receiver:
http://www.uni-go.com/proddetail.php?prod=T3280
The coupling inner liner:
http://www.uni-go.com/proddetail.php?prod=T3290
A youtube video "UniGo Trailer Demo": [It takes a while to see a
couple examples of hitching and unhitching though.]
http://www.youtube.com/watch?v=9GDypdAg_2g
This web page has 3 better pics of one hitched up with
a hitch pin lock on it:
http://www.roadrunner.travel/2013/09/10 ... o-trailer/

A Uni-Go Dealer website: In TX
http://www.uni-go-trailers.com/
Their page with specs on the Uni-Go:
http://www.uni-go-trailers.com/TrailerUni-go.html#specs
Their FAQs on the specs page says the needle bearings are replaced
with nylon bushings to eliminate slop that would create isability at speed.
Would this be a concern for your design ?

A good pic illustrating the Uni-Go:
[Click on pic for larger view]


Another motorcycle single-wheel trailer make with their own take on it:
http://www.thirdwheeltrailers.com/
Go almost to bottom o the page and look at "Cruiser Version of latching System":
http://www.thirdwheeltrailers.com/index ... lers_specs
A pdf brochure, not alot of specific info though:
http://www.uni-go-trailers.com/Files/Th ... ureTTP.pdf


-----------------------------------------------------------------------------------------------------------------
INFO FROM:

TheElectric Vehicle Technology Forum
http://endless-sphere.com/forums/viewto ... 4&start=25
There is some discussion on the 2axis set-up here.

From there, here's a link to another maker that has its own version of a 2 axis
hitch, not necessarily like a specific U-Joint form but the same action: I wonder
if this is more a more robust design?
http://n-line.com/
http://n-line.com/products/single-wheel ... e-trailer/
Look under "Pricing and Options" at "tongue Stand" and "Chrome
Grab Handle" for a better look at the trailer portion of the 2 axis hitch:
http://n-line.com/pricing/
This may be the tow-vee receiver adapter to hitch to the trailer:
http://n-line.com/wp-content/uploads/20 ... daptor.png
There are some pics showing how they are hitched up in the showcase:
http://n-line.com/category/photos/showcase/

Here's a posted pic showing a home made 2axis hitch descibed:
"And here's a Harley hitch. It will swing left/right, and up/down, but it won't rotate, so the one-wheel trailer leans with the motorcycle. Its home-made from a cars driveshaft U-joint because they are cheap and strong..."

This may make people get a better understanding of your proposal:
[Click on pic for larger view]



And here's a link to a forum that a poster recommended for Motorcycle trailer Towing that
supposedly has some good discussion on the topic as well as single wheel vs double wheels:
Main Page: [The link worked initially but not on a recheck, maybe it'll work later]
http://forums.delphiforums.com/n/main.a ... 2132626784

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It seems there has also been some discussion here on TnTTT on the topic [RE: for a motorcycle] in the Foamie section's biggest thread "Thrifty Alternatives ... Building Foam TDs"
p284- 285, by forum member theWolfTamer, et. al., with a pic of another homemade 2axis
hitch on his 05-06-12 12:17am post, viewtopic.php?f=55&t=39373&start=4260 [pg285].

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There's also a couple examples of other vintage 2axis hitches on here:
http://www.singlewheel.com/Scoots/UnidentifiedFR.htm
Check the third line down 1st two pics and the fourth line.

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Finally, here are a couple Ausralian multiaxis trailer hitches/couplings that use the
U-Joint - or the principle of it - in their designs:

The McHitch Uniglide Trailer Coupling
http://mchitch.com.au/

This is a multiaxis hitch based on using the same U-Joint that is used in Toyota Landcruisers:

"The most important feature of our couplings is the use of a universal joint to handle all of the horizontal/vertical movements, well past 90 degrees horizontally AND vertically (nothing else on the market comes close) with the twisting being handled in the rear body by shock absorbing urethane bushes. The universal joint itself is the same found in all 4wd Landcruisers (industry part no RUJ-2041 made by Toyo Japan). The joint itself is held in place by registers and opposite threaded plugs/end caps which removes any end play. The universal and the rear body are both fully greaseable."
It has 2 to 6 "tonne" ratings and has been tested and certified per AU regulations.
[Not to be confused with http://www.mchitch.com which is a US company that makes regular
style hitches for motorcycles.]

The OZ Hitch:

Here is another, perhaps a simpler more straightforward design, using the U-Joint princple:
http://ozhitch.com/
It has 2 to 3.5 "tonne" ratings and has been tested and certified per AU regulations.

If you eliminated the horizontal rotating axis in these, you'd end up with a very robust 2axis
hitch.

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'Found another pic of a homemade 2axis motorcyle hitch:
[Click on pic for larger view]


Here's a youtube video on a homemade single-wheel with 2axis hitch:
http://www.youtube.com/watch?v=8kcWEjpOF6Q

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I'm not wanting to clutter up your thread with all of this, but I thought that perhaps this
info could help show others the gist of your hitch and the build.

I now think that your proposal may work very well. For some unknown reason, I had
envisioned the small diameter arms of the U-Joint being subjected to the rotational
forces/torque of the whole trailer along their lengths, whereas both are actually operating
90 degrees off of that, and the way they are positioned is the way that they were designed to be
used. I'd be surprised if the torque imposed by the body of the trailer, as it rolls side-to-side,
is more than what has been imparted to the U-Joints in their more usual operation. But that
should be ultimately determined/proven by the engineers utilizing their mathematical formulas to
analyze it all. But just from the pics that I've seen so far - and as linked to - those U-Joint based
hitches, at least for motorcycles, appear to be at the least, robust enough to handle their job.
["Robust" is the word of the day...]

I do have a question though. Since the wheel is essentially at the far end of the trailer, away
from the tow-vee, there is obviously a much heavier "hitch/tongue weight" involved here. I'd
guess at least half of the trailer weight is tongue weight, and the tongue weight may even be
more depending on how it is packed for travel. [I've never taken physics - just using common
sense here.] So, that tongue weight is a 'carrying load' you are imposing on/off the rear/rear
axle of your tow-vee. Will the Subaru be able to handle that much extra load ? I'm guessing
you have one of the smaller body sized ones, based on you mentioning '1600cc s'. Do they
even make helper springs - or air shocks - or assist air bags for your model ? And will the rear
tires still be within their load capacity ? 'Just trying to help cover all the bases here...

Cheers,
Norm/mezmo

[KCStudly]

Norm has really out done himself on the research this time! Good job.

All of that said, remember that a motorcycle has drastically different handling characteristics from a car. The rider uses steering input to shift the CG to make the bike lean into a turn. (Believe it or not, this is intuitively done by first turning slightly in the "wrong" direction and as the bike tips in the way you actually intended to go, gets corrected for... true!). Because the CG is constantly being managed in check with the lines of force, it seems to me that the relative torsional loads through the hitch in a motorcycle application would be less than in a car application.

In other words, the torque vector in a motorcycle is minimized by leaning into a turn, whereas in a car would be magnified.

[WeirdDogGuy]

Holy Cow Norm. You must have been up half the night putting that together so thanks. Don't worry about cluttering up the thread, it's good to have all the info in one spot and I suppose this thread is as good a spot as any. I haven't had time to go thru it all but I will in the future. There is something that I wanted to stress. I know some are concerned about the size of my u joint. Size is important fweep fweep but my main consideration was angulation. Here is a pix of some u joints out of my scrap pile:

avll12(1).jpg (227.93 KiB) Viewed 1597 times

The u joint that I'm using for my build is the one on the far right. All the u joints in this pix are bottomed out. Their yolks are touching and they can't bend anymore. My joint goes past 90 degrees. Now look at the joint next to it. It can only swing what, say, 30 degrees either way. So my total swing is 100+100 or about 200 degrees (right and left combined). The other will give somewhere around 30+30 or 60 degrees total. *VERY IMPORTANT* What happens when the yolks bottom out because they have reached their limit of swing???????

It depends. One of 2 things will happen. Because you are busy driving the car and you don't realise that your u joint is at its limit, you continue your turn and then you will either fold your trailer in half or the tires will slide slideways on the pavement. Can you see that? It's *VERY* important to understand this if you are designing with u joints. Use the one with the most flexibility that you can find. Of course, strength is important too.....

Thx again for putting that summary together. Andy

[WeirdDogGuy]

I do have a question though. Since the wheel is essentially at the far end of the trailer, away
from the tow-vee, there is obviously a much heavier "hitch/tongue weight" involved here. I'd
guess at least half of the trailer weight is tongue weight, and the tongue weight may even be
more depending on how it is packed for travel. [I've never taken physics - just using common
sense here.] So, that tongue weight is a 'carrying load' you are imposing on/off the rear/rear
axle of your tow-vee. Will the Subaru be able to handle that much extra load ? I'm guessing
you have one of the smaller body sized ones, based on you mentioning '1600cc s'. Do they
even make helper springs - or air shocks - or assist air bags for your model ? And will the rear
tires still be within their load capacity ? 'Just trying to help cover all the bases here...

Cheers,
Norm/mezmo

The rear suspension of early model Soobs is a torsion bar set-up similar to a VW bug. I can jump a spline on the torsion bar and that would get me more lift but I just don't think I'll need it. I am building light and one of the benefits of doing so is that I can leave the Soob stock.

[mezmo]

Your Welcome Andy,

I just had a thought, after reading your explaination on the angle limits of the U-joint
and how that will affect the turning on the proposed hitch set-up.

Would a CV-U-Joint give you a larger movement range or a smoother movement over
a 'standard' U-Joint ? Or would that just give too much 'flexability' ?

I thought that that may be a possibiity since it seems a CV-U-Joint must have tremenously
more forces to deal with than a 'standard' U-Joint and needs to have a smooth movement
or reaction in its turning and movements up-to-down and side-to-side. Plus,from a very
cursory looksie at this Google Image search on the " cv u-joint " [I'll click on am image that
looks interesting and check out the corresponding website:
https://www.google.com/search?q=cv+u-jo ... 2#imgdii=_
Some designs appear to be almost a couple of u-joints back-to-back and that could extend
the angular limits a bit eh ? Or is that not a CV-U-Joint, but just a kind of compound U-Joint?
Or is that a type of CV-U-Joint ?

I haven't had time to look into these links, but they may be a place to start, perhaps.
I just wanted to include them here for future reference.

http://www.fourwheeler.com/search/?q=cv ... 0u%20joint

http://www.fourwheeler.com/how-to/1006o ... ng-torgue/

Cheers,
Norm/mezmo

[KCStudly]

I think that under braking a double U-joint CV would be like "pushing a rope". Ball and groove CV's (not sure what the proper name is for these), like in most FWD cars generally have less articulation than an equivalent std. u-joint.

[WeirdDogGuy]

I agree with KC. I think multiple cv joints would have too much flexibility. It would act like a short length of chain.

I welded my torque tube spine last week. I also clamped my floor irons to the spine and I was about to weld them when I realized that they would be much easier to paint if they weren't welded on. They are small steel box beams (sq tubing) and since they will rust from the inside out as well as outside in, I painted the insides. I stood them up in a gallon of enamel, then I hooked a piece of foam to a length of coat hanger wire. I could then swab the interior of the tube with my diy foam brush. I didn't paint the end that I'm going to weld to the spine. They are dry now and ready to weld onto the spine.

avll15.jpg (78.94 KiB) Viewed 1519 times

[KCStudly]

Totally by coincidence, today I learned something about the double cardan style joint that I did not know when I wrote the "push the rope" comment. They have a ball and socket hidden in the center link that maintains alignment.

Ask me how I learned this. My coworker buddy Larry had this ball/socket joint fail on the front drive shaft of his '04 Rubicon. At highway speed, within seconds the vibration was sufficient to shatter the front drive portion of the transfer case housing, leaving the output chain hub and drive shaft flopping in the breeze between belly pan and frame and the drive chain dangle down. Nicked the high pressure fuel line and took out the wiring harness. Amazingly, after removing the drive shaft, he was able to limp in the rest of the way to work (about a mile or so) where he brought the carnage in for us all to see.

Here is a link to a cross section of a double cardan u-joint. I still don't think the complication is necessary in Weird's application, but it is interesting to know.