Home-building a uni-trailer

Art Franz

Art Franz

Joined
Jan 6, 2010
Messages
347
Location
Lacombe, AB Canada
Bike
05 ST1300
I'm in the process of building a single-wheeled trailer to pull behind my ST1300. I'm wondering how long I should make the tow-hitch; is there a formula that will says what the distance should be between the wheel and the point at where it swivels at the hitch? (In this case a u-joint.)
I know that if it's too short, it will contribute considerably to the trailer wobbling/weaving back and forth, but at the same time, I don't want it any longer than it needs to be.
Any and all input would be much appreciated.
 
I know what the guide line would be on a 2 wheeler, but I do not know of one for a single. If you are building it like many of us have with the wheel at the rear,then I do not think you can go too short. If you are going with the trailer wheel at mid load then that could be another question all together. If I were to build a mid wheel trailer I would put the wheel with adout 1/3 if the load behind the wheel, and see what happens.
 
Art, HERE'S my writeup of my one-wheeled trailer "I-Lean". I don't have the exact dimension (from pivot to axle) but I'm guessing it's about 60". George's trailer was built by Kreis (H2Orider) who has built several one-wheelers.

Gus1300 said:
Personally, I would think a single wheeled trailer would be VERY unstable...:think1:
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There are many of us with various one-wheel trailers that would beg to differ. With proper loading (critical with ANY trailer) and suspension setup my trailer pulls like it's barely there, from walking speed to triple digits.
 
I too am in the planning stage for a single wheel trailer. With all the ideas and info available here it should make for a smooth build.:rd13ug:
 
That's easy to figure out. Estimate the total weight of the trailer and its center of gravity. Estimate the distance from the center of gravity to the center of the trailer wheel. The ratio between the CG to wheel distance and the total length of the trailer will determine the tongue weight. in the example below, say we have an estimated trailer weight of 100 pounds, plus a cargo weight of 80 pounds, with the CG 20 inches in front of the trailer wheel. If the distance from the hitch to the center of the trailer wheel is 60 inches, the tongue weight will be :

20 in = 60 pounds
60 in = 180 pounds

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The longer the tow hitch is, the lighter the tongue weight.

In this example, the center of gravity is way in front of the trailer wheel, so it has to be stable. If the wheel is centered on the trailer platform, the same formula can be used to find out the tongue weight. Too small a tongue weight means that the center of gravity is real close the the trailer wheel, and that leads to instability. I think that the tongue weight should be at least 30-40 pounds. Not enough to matter on the real wheel of the motorcycle, but enough to ensure that the center of gravity is always well in front of the trailer wheel.
 
Ah, wasn't thinking outside the container enough...am only familiar, and not even that much so, with ball joints...hence my misconception of roll instability. Thanks for the link to pictures, using a u-joint to stabilize roll axis while maintaining U/D and L/R swivel illustrated the concept very nicely.
 
I am also currently building a uni-tire trailer. I have gotten so far as a test drive with the chasis. I mounted a camera in back and when I got back to the house I checked it out. Found some interesting things that I had not considered. The u-joint was not turning enough to make sharp turns without dragging the tire around (fixed that), the tire was a tight fit in its assembly and at speeds over 70mph, the tire expands in diameter and rubbed the frame (fixed), I also found that the front of the chasis needed more bracing. It was taking up some of the bounce away from the shock and that could damage the pod once it is installed on the chasis. Last thing I saw was some instability on left anf right wobble. This was due to the hitch not fitting tightly on the bike's tow bar. It is not rock solid. I hope to do another chasis road test this week. I will post the chasis as it is in my albums in the event someone wants to give me better ideas.
 

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As Pat mentioned, Kreis Weigel built my trailer. He's built several with good success. The universal joint "hitch" provides all the stability ya need. Mine pulls almost like it's not there. No appreciable effect on gas mileage either. My tongue weight is probably 25/30 lbs when fully loaded. I place the heaviest stuff at the back, of course, but the box fills up sometimes. :D
 
DakotaJoe said:
I am also currently building a uni-tire trailer. I have gotten so far as a test drive with the chasis. I mounted a camera in back and when I got back to the house I checked it out. Found some interesting things that I had not considered. The u-joint was not turning enough to make sharp turns without dragging the tire around (fixed that), the tire was a tight fit in its assembly and at speeds over 70mph, the tire expands in diameter and rubbed the frame (fixed), I also found that the front of the chasis needed more bracing. It was taking up some of the bounce away from the shock and that could damage the pod once it is installed on the chasis. Last thing I saw was some instability on left anf right wobble. This was due to the hitch not fitting tightly on the bike's tow bar. It is not rock solid. I hope to do another chasis road test this week. I will post the chasis as it is in my albums in the event someone wants to give me better ideas.
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Just was wondering what you are using for the tire and rim and for the shock.
 
DakotaJoe said:
Last thing I saw was some instability on left anf right wobble. This was due to the hitch not fitting tightly on the bike's tow bar. It is not rock solid. I hope to do another chasis road test this week. I will post the chasis as it is in my albums in the event someone wants to give me better ideas.
Click to expand...

There is a bit of "slop" in mine, where the hitch goes in the receiver. I don't think it's an issue. You can feel it, from time to time, but once rolling it's barely noticeable. I think this bit of slop prevents the trailer from inducing sway/wobble in the rear of the bike.

Are you planning on making a metal box or some other type of container??

EDIT: I checked out the pics, forgot you had the Unigo box. Looks GOOD!

Toaksy said:
Just was wondering what you are using for the tire and rim and for the shock.
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Looks like a scooter wheel/tire and a bicycle shock to me, but correct me if I'm wrong.
 
Yes, the tire came from a scooter. I wanted to go larger than what Uni-go used. The shock came from a mountain bike, rated at 750 lbs. The lbs only applies when it is on that particular mountain bike. The way I built my trailer, I can stand on the chasis and it drops down about 4 inches. That is more weight than I will put in it of course. I have one more weld to do tonight and it will be time for another road test with the chasis. Fingers crossed.
Toaksy said:
Just was wondering what you are using for the tire and rim and for the shock.
Click to expand...
 
I am using a 1 1/4" tube reciever for mounting the trailer. I retooled the hitch pin hole and now I have a very solid connection. NO Wobble. I think this will help. I really felt the wiggle from the first test ride.
sirepair said:
There is a bit of "slop" in mine, where the hitch goes in the receiver. I don't think it's an issue. You can feel it, from time to time, but once rolling it's barely noticeable. I think this bit of slop prevents the trailer from inducing sway/wobble in the rear of the bike.

Are you planning on making a metal box or some other type of container??

EDIT: I checked out the pics, forgot you had the Unigo box. Looks GOOD!



Looks like a scooter wheel/tire and a bicycle shock to me, but correct me if I'm wrong.
Click to expand...
 
I have taken my home built uni-tire trailer out for a test drive. I video taped it and it is on You Tube under the title of, "Uni tire trailer test run". I will try to attach it's link. My alterations I made have fixed all my issues. I will try and finish making it pretty this week and getting it painted. Next thing will be making a rear fender to accomadate the larger tire and wiring the pod and painting the pod. Mount and lighting. I posted a lot of pictures with descriptions in my albums. I will add to as I continue the build. Ideas and questions are always welcome.

[video=youtube;QBV_u7KHAXo]http://www.youtube.com/watch?v=QBV_u7KHAXo&feature=youtube_gdata[/video]
 
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