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Mechanically connecting a trailer to a motorcycle

6K views 39 replies 15 participants last post by  meshego1 
#1 ·
This post will likely leave riders with more questions than answers. We have been really busy for a year in developing a new source for aerospace bodies for the Tailwind and this has resulted in my not having time to visit this really good board for several months.

For those of us accomplished in various fields, things seem obvious. However, how often do we think about a person that has never had a reason to be versed in our field and would not be expected to make correct decisions in that field. Like having problems with MS Excel and going to MS for help. Their answers always assume that you know almost as much as they do. So to get help in Excel it is best to go to a third party.

Pulling a trailer with a motorcycle is often assumed to be a non technical issue, like eating ice cream needs a spoon instead of a fork. Of course nothing could be farther from the truth. What brought this to mind was the thread about a broken Rivco receiver.

First off it was a broken ball plate. The receiver is what it plugs into.

I have been there and done that. I designed my first motorcycle pulled trailer and built it in 1957. I patterned it after a Wright auto camp trailer and just made it motorcycle size and out of aluminum instead of steel. Since that time I have had 40 years of aircraft structural, mechanical, and aerodynamic design experience and also several years in other fields. But the knowledge of baptism by fire in those early months in 1957 were deeply etched.

Making a trailer so it can be loaded nose light is like selling arrows with the feathers on the point end. (My first trailer was just that way.)

Riders that are not steeped in physics will almost universally think that a trailer on a bike should be loaded to have minimum down load on the hitch. This is as wrong as jumping off a building and flapping your arms to reduce the impact. Years ago when Hal Greenlee was kind of the owner/sponsor of this board, I read the post of a rider that had just crashed pulling his trailer with his wife as a co rider. He said he did not know why the rear tire of his bike failed because he had nearly zero tongue load. I cringe to see these kinds of stories over and over.

What happened was that he loaded his trailer near neutral and successfully pulled it in this highly unstable condition until he got a leak in his rear tire and as he tire started to be low, it reduced the lateral stiffness in the rear of his bike and the typical divergent oscillation happened and threw them off the bike. By the time he got out of the hospital and to his bike, the rear tire was all the way flat so he assumed it blew out.

I have posted information on this subject before but it has been years. When I see things like these ball plate failures and comments like the weight on the hitch was not very much, I realize that I need to bring this up again.

IT IS NOT THE WEIGHT ON THE HITCH THAT IS THE PROBLEM WITH BREAKING THINGS, IT IS THE INERTIA.

You can easily take a 2 wheel flat bed trailer and put 4,000 pounds of cement bags on it that are stacked in such a way to have exactly zero downward load on the hitch. You could sit there and hold this trailer level at the hitch with one hand. But, if someone paid you a thousand dollars to raise that hitch 3 inches and put it back down 3 inches 5 times in one second, you could not begin to do it because the dynamic force to do this would be in the thousands of pounds.

Postured another way, likely you can hold a 50 pound anvil in your hand. Also if you suspended this anvil with a bungee from your hand you could move your hand up and down very quickly while it was suspending this anvil, but if you had the anvil in your hand you could not move it up and down quickly because of its inertia. The Bungee would be relieving of the inertia.

Because of the dynamics of pulling a single axle trailer with a vehicle, the trailing vehicle must be nose heavy by at lest 10% and better if 15% to be stable. Dynamics are everywhere that things move. Airplane ailerons, elevators, rudders must be nose heavy or they will flutter and fly off the plane or take the surfaces they are attached to off the plane unless they are irreversible, meaning they can not be made to move as in transonic and supersonic aircraft.

People designing trailers and trailer hitches are not necessarily physicists, nor or the riders using them. Terms like notch sensitivity and stress risers are not in their vocabulary. Opinions will not make or prevent failures but there have always been lots of opinions.

If there is no inertial relief system in the mix, then the dynamic loads must be within the capability of the structure applying the loads including the fatigue spectrum.

Steel is typically more tolerant in fatigue than aluminum but steel airplanes would not be able to carry much. So the aviation industry has had to establish and live by certain parameters relative to fatigue. There are a lot of very old airplanes flying, like B-52s.

It is probably well known that certain trailers have had lots of failures in certain areas and that is because there was no effort to reduce stress at these failure points. A 3/4 inch diameter shaft has a fair amount of strength but if you want it to fail, make it an extension of a large shaft turned down to 3/4" in a single sharp step or to put any kind of a stress riser in the design. If the dynamic load is high the shaft will break exactly at the step in diameters or other stress riser. History convinced one of the manufactures of this when my words could not.

Similarly, if you have a beam, say a foot long, and you apply a load of 100 pounds, the bending load at the root end will be 100 foot pounds and so its connection to resisting structure must be good for 100 foot pounds. If the beam is extended to 5 feet, then the bending load at the root is 500 foot pounds and so the joint receiving the load now must be 5 times as strong as it would be for a 1 foot beam. All of these of course must be good for the load applied when applied 1,000,000 times or however many cycles the life time of the joint needs to be. Armed with this kind of inquisition, it is obvious that many trailers are not prepared for long term use.

In similar thought, Honda did not do us any favors when they needlessly extended the plastic by almost half a foot aft. The most stable place to attach a trailer to the bike is where the rear tire touches the pavement. Obviously that is not in the cards. However, every inch aft and up from that point is going away from stability. Also, because the frame of the Wing was not changed, the hitch manufacturers kept their core mount structure and just made the ball plate longer. Remember the increase in bending moment on lengthening beams. Our Tailwind users have come up with a way of carving an arch in the rear fender so that the pre 2012 hitch ball location still works. This is low risk because there are so many center fender panels left from trike conversions.

Bushtec recognized that their rod end type hitch had limited travel when the bike was nose up compared to the trailer and recommended hitting steep drives at an angle. I do not know if some trailer/hitch combinations using a ball might run into a similar nose up limiting angle. The fact that some of these failures are at the ball end of the ball plate on Rivcos makes me wonder if that could be the case. Then too, when bending metal, when the plastic limit si reached granular separation starts. That gets into bend radius, hardness at bending temperature, etc..

My failure to convince those I wanted to buy trailers from on some of these issues, caused me to re enter the manufacture of trailers with the Tailwind in 2003. It has been very enjoyable with countless friends that I might not otherwise have, but I will admit that Aviation was more lucrative.

It is said that a person's wealth is measured by what he has that money can not buy. I would not think of trading anything for the friends I have in these motorcycle touring associations and particularly the Tailwind family. My longest lasting and best friends have mostly come from motorcycling. My friend Hilmer Merz and I have been riding together since 1959 and we each have great grand kids whose grand parents were our kids in diapers when Hilmer and I met.

Glen Kenny's enormously popular RTE is proof that Motorcycling families are naturally great friends.
 
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#3 ·
:thumbup:So if i read this rite on newer 2012 n up with longer rear fender tallwind guys cut notch in fender ???? To accommodate new length of fender ? Any chace on a pic what they did. Old hitch works fine but issue as stated with length of bar.good rite up !!
.
 
#4 · (Edited)
Have not posted a pix in a long time so here is trying. This is a photo of Len Ellis' bike and also shows where the six pin round socket was placed, since the 2012 and later bikes have a frail three piece bottom fairing of the trunk and will not support the six pin socket there.

This trim accommodates the screws in the bottom corners that attach to the saddle bags. The Rivco hitch ball plate is the ORIGINAL 6 inch drop ball plate, that is for 2001-2010 Goldwing models. Not the new stretched out ball plate.

Although we have not tried it yet, I believe the ORIGINAL short flat ball plate for the Bushtec Hitch will also work here. It is all but impossible to get someone at Bushtec to find and ship the original short Flat ball plate. Nevertheless, some of our customers have been successful in getting them to do it.
 

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#5 ·
Have not posted a pix in a long time so here is trying. This is a photo of Len Ellis' bike and also shows where the six pin round socket was placed, since the 2012 and later bikes have a frail three piece bottom fairing of the trunk and will not support the six pin socket there.

This trim accommodates the screws in the bottom corners that attach to the saddle bags. The Rivco hitch ball plate is the ORIGINAL 6 inch drop ball plate, that is for 2001-2010 Goldwing models. Not the new stretched out ball plate.

Although we have not tried it yet, I believe the ORIGINAL short flat ball plate for the Bushtec Hitch will also work here. It is all but impossible to get someone at Bushtec to find and ship the original short Flat ball plate. Nevertheless, some of our customers have been successful in getting them to do it.
It was a simple phone call for me to get the flat ball plate.
When I called, I was told that it would be a week or two because it took time to get them back from the chrome shop. I told him I did not want it chromed and got it in two days.
 
#7 ·
So came across this and wanted to share as Tom's original post to this thread touched on this issue.
And in my recent trip I noticed quite a number of trailers (mostly attached to cars and trucks) that were suffering from lack of understanding...
I think this makes it VERY clear why a forward bias in weight distribution is highly desired
 
#10 ·
I know this is reviving an old post but hope Mr Finch sees it. I take everything he says about trailers as gospel. I used his directions to have the bearing spacers on my Bushtec trailer custom made to fit the individual wheels to prevent possible bearing failure. Just as he predicted, the ones from the factory were a few thousands too short and resulted in the bearings seating improperly. Also had a spare wheel done to be safe. One day I hope to have a yellow Tailwind in my garage.
Tom, I saw you at Glen's RTE this year but unfortunately I received a call from my wife about a family emergency and had to leave soon after I arrived and didn't get a chance to shake your hand which was one of my main reasons for finally making the trip. One day I hope to meet you and take delivery of a new trailer in Spring Branch.
 
#11 ·
Johnny, That story makes me feel bad. I hope the emergency got sorted out quickly. The Tailwind thing has allowed me to meet so very many great people. The Tailwind owners and their friends have become a great big and wonderful family. That extends to all who pull trailers and from there all who tour on motorcycles. At the age of 80 I am 4 years out of warranty and next month I click of another one.

Several original Bushtec owners now have a Tailwind so take heart! Rick Straub rode with us on our TTTs for some years pulling his Bushtec and finally got his Tailwind some years back. In a remote way, Rick is responsible for the rain at Glen's RTE. He has a friend that often rides with him who's nickname is Splash. When every splash is along, it rains which is how he got his name. Of course Splash was there at Glen's.

Of all the rains I have ever led a group of riders in, the 2011 TTT side trip one afternoon from Blanding to the Mexican Hat and Monument Valley was by far the worst frog strangler ever. Splash was along. However it was my fault for taking the route through Monument Valley because my radar showed no rain there. I found out later that there was no Radar there. The most vicious lightening, the most trucks hauling uranium ore, the highest wind, just one of those rides that no one has ever forgotten.

Johnny I hope we get to see each other again soon.
Tom
 

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#13 ·
That Installation looks good! Be nice if you could get one of Zachybilly's hitch balls.

This compromise may require a bit more care when backing with the trailer coming around, but the improved stability is worth the effort. Next time you have the ball plate out, please take pictures and dimension the distance from the post to the ball center.

Your mud flap closure looks good but I can not tell how far from the pavement the bottom is. The lower it is without actually dragging, the better.

Thank you for posting.

Tom
 
#14 ·
It is the short straight Bushtec. It doesn't have any bend. I know some don't like swivels, both my Hannigan and Rollahome have swivels.
Trying to show the difference in lengths of the 2012 bar and the pre-2012 bar.
 

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#15 ·
Thank you. I did not realize it was the original length. So you answered a question I have had since the 2012 came out and hat is that the original length Bushtec Ball Plate does work if the fender panel is modified.
 
#16 ·
What happened was that he loaded his trailer near neutral and successfully pulled it in this highly unstable condition until he got a leak in his rear tire and as he tire started to be low, it reduced the lateral stiffness in the rear of his bike and the typical divergent oscillation happened and threw them off the bike.
That point about the lateral stiffness in a motorcycle tire is scary. Shortly after leaving Missoula, Montana in Sept. 2009 my rear tire started to go flat and I vividly remember how unstable the bike's rear was at 75 mph on the expressway. By the time I got off the expressway and parked, the tire was almost entirely flat.

That is why I have used a run flat car tire ever since.

I also believe that anyone that pulls a trailer should also have a run flat tire.

Thanks for the thorough discussion in post #1.

gramps

.
 
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#19 ·
I'll recheck next time I hook up to trailer, but the hitch swivel almost always falls over to the left. Very seldom flat or falls to the right. I think it was over on its left when we checked how sharp I could turn. I I know I was making left hand turns and it seems the hitch was over all the way on its side. I know what ever one says are the negatives of a swivel hitch, but for me and my opinion, the positives out way the negatives.
 
#20 ·
If you can lay the bike on the guards with a narrow necked ball and standard hitch coupler, would like to understand the swivel thing especially with Dave's trailer which is quite stable. I always like to learn what is everyone's mind relative to pulling trailers with bikes.

A trailer with a propensity for rolling over I would understand. I certainly appreciate your comments and photos. Thanks much.
 
#24 ·
If I am understanding your description, that of a trailer with axles on both ends with the front one steering, that is called a wagon type trailer which I have pulled with a car. I even backed it. it takes a mind understanding second order effects to back such a trailer. Not reasonable to pull without brakes.

Another variant is a dolly like that used to piggy back trailers wth semis. I have see that lash up with bike trailer before. Not meant for backing up.
 
#23 ·
Welcome back Tom,
I have always enjoyed your explanations. You are one engineer that makes sense to me, that does not happen often...

Thanks for sharing what you have been given.

Mike
 
#25 ·
Mike, Thank you for the comment. To me an engineer is a guy that operates steam locomotives which I never got to do but would have loved as a life.

Starting when I was 10 years old, I spent many a Saturday morning walking around he MP roundhouse in San Antonio whenever the supervisor was not there. The guys changing boiler tubes or making rod bearings got used to this kid being everywhere around and they would warn me before the super showed up. I learned about metal fatigue when I was 11 years old and made a suspension for the trailer I had made for my bicycle that I carried my baby brother in. The platform that carried the axle was attached along the front edge with a row of nails and there were bed springs on the back edge. The nails fatigued so I switched to barn door hinges and that worked out well. I built a large crossbow from scratch when I was 12, finding out soon that lemon wood that was said to be good for a bow was unreliable so my second choice was a piece of spring steel from St. Louis Spring Company on Avenue E. I selected 1/4" by 2" by 60" and did my grinding and drilling and took it back to them to temper. The trigger mechanism was rough and had to be refined, and several iterations took me to 1/8" aircraft control cable before there was a bow string strong enough. The first time I fired it knocked my skinny body several feet backward and I hit on my back and head. It would shoot very very hard but not very accurate.

I guess I never stopped designing and making things because it was too much fun. Because I was designing bass horns I met another audiophile who was Ed Swearingen. At the time he was helping Bil Lear design the L2 Auto pilot but he decided to start an airplane company and build a business twin called the Merlin, making a new body to fly on Beech Twin Bonanza Wings and horizontal tail. His next step was a whole new airplane so he had a group of engineers designing a P-51 airfoil wing. I walked buy them one day on my way to where the pipe organs we built were happening and saw these engineers designing the wing flaps with Ed telling them how he wanted it done with four-bar links. Knowing unsolicited advice was seldom appreciated, I told Ed that his links would be subjected to twisting because the wing was tapered and therefore the motion lines would fan out and back. Ed said that wouldn't hurt because the links would just wind up. I said bad design and for the first time in our some years friendship he got mad at me and said "if you are so f****ing smart go design the son of a B***ch your self" So I did. Then the ailerons. Then the landing gear. Gust lock, Flap interconnect, and on and on and soon was the head of R&D of Swearingen Aircraft.

Fortunately, over time I had some chances to do things and got to be with some very neat people. Bill and Moya Lear, Sam Williams, Clay Lacy, Sir Ralph Robbns, Norm Wilson and many others called me Tom or Tommy. One night there was a kick off Diner when the company I worked for, DHC, won the contract to build the flying command post for Saudi under King Fahad. Jim Austin, top engineering manager at that time for Boeing addressed me directly from the podium at the dinner and said we (DHC) would never be able to certify the massive job with the FAA. Probably 75 very high level people at that dinner in Seattle. We did certify it and Boeing Ops management said that I knew more about the 747 than any man alive. That just simply was what needed to happen because we had done what Boeing said was the larges modification of an aircraft in the world. Boeing had people that knew a lot more about landing gear than me and others that know a lot more about control rigging than me but no one in Boeing needed to know the whole airplane. The 747 was designed by several companies like Northrop, and others who each had a part of the plane to do.

I still liked steam locomotives and motorcycles. I did airplanes because they needed to be done.

Guess I got runaway fingers again.
 

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#26 ·
Hi Tom,
Thanks for sharing your life.
What a great story! Sounds like a life well lived.

Looking back, what would you have done differently?
What kept you going when things got tough?

Appreciate your thoughts.

Best,

Mike
 
#32 ·
Mike, what kept me going was having so many friends. I feel lucky to have been born and lived in an era when most people were honest and responsible. Was normal in those days to leave your keys in the car and no one knew where the key to lock their house was. As a kid, there were so many things to see and with no TV we took time to look around. On weekends and in the summer, I rode my bicycle where ever I wanted to go from the time I was 10 years old. My parents did not worry that something bad would happen.

The San Antonio City Water Board had a facility down town that had two 3 cylinder steam engines pumping water. One was put in in 1908 and the other in 1911 and they were hauled in by mule team. They had twin 18 foot diameter flywheels and turned 30 RPM. The newer one had never been overhauled and pumped 400 gallons of water per stroke. The service man jumped on the connecting rode and rode it around while putting oil in the oil cups. Had beautiful polished brass valve rods and staged cylinders 4, 5,and 6 feet in diameter.

At Scobey's cold storage were two large diesel engines that turned alternators direct drive. These alternators were about 5 feet in diameter. One engine had 5 cylinders and external valve rocker arms and was fascinating to watch also. Large electric motors that pumped ammonia to make ice and chill the storage vaults were scattered around the facility, powered by those diesel generators.

While I was in grade school at St. Ann's a new church was built next to the old school and church building. The foundation piers were excavated for by mule powered drills. I was fascinated to watch these work. I was not an academician but was the student that kept things working like fans and other appliances while in grade school.

Anything technical was where I spent my time growing up. Kinematics was a fascinating subject. My mother had three brothers and my favorite one was a mechanic at a Pontiac and Case Tractor dealer up in the Panhandle where I was born. No one could tell me how a differential worked so I looked forward to him coming down for a visit. Unfortunately he could not tell me how they worked either I was 8 years old and guys needed to know these things. So I went to the library and learned how they worked. Well into my working career I saw a clever device used in aviation that showed the pilot of a twin engine airplane when the engines were in sync so there would not be the heterodyning drone of out of sync props that drove the passengers nuts when the pilot could not sync the engines buy ear. The engine speed indicators actually had synchronous motors driving them from three phase signals from little alternators on the engines. So this clever individual had put two motors driving opposing shafts into a differential and what would be the drive shaft in a car was a pointer on the instrument that would stand still if both motors were running at the same speed. I reasoned that if you had infinitely strong equipment and reached in and turned that pointer with a big pair of pliers that you could force one engine to run faster and the other slower. Taking this concept to practice I developed a steering transmission that had two planetary drives, one for each wheel and made it so the ring gears could be counter rotated by a different motor. We patented this and developed the OmegaTrack front wheel drive power wheelchairs. Was also used in Dreadnaught battlebot.

Things I regret. Being caught out in New Mexico on a Saturday Night with no place to stay and having the drunk kill my youngest and paralyze the next youngest. I did not know the drunken state there.

I am glad my 6 kids came early. All six in grade school at the same time. I was the biggest kid of them all. We camped a lot. Traveled in unorthodox ways sometimes. My daughter that passed away this Christmas said it was the very best childhood anyone could have had. We will spread her ashes in the Rocky Mountains of Colorado next Saturday where she wanted. She loved being there camping as a kid along with the rest. Those of you with kids, never miss the chance to hug them.
 
#28 ·
When I was growing up we had 4 wheel wagon type trailers. We had hitches on the front bumpers of the pull vehicles that were used for backing the wagons. I would not want to pull this type trailer with a motorcycle, especially at speed.
 
#30 ·
Don't remember seeing any motorcycles pulling 4 wheel wagons at highway speed. Has been long ago but the wagons I remember had more of a tendency to wag/weave when pulled at speed especially if there were problems like low tire pressure, too much free play in front axle or incorrect wheel alignment. I am sure one built with modern components will pull better. Trailers like the tailwind can be safely pulled fully loaded at speed and with very little change in fuel mileage.
 
#31 ·
Since I didn't have a chance to show you( Tom) what I did on my hitch when we were in Jasper a few weeks back I thought I would attached some pictures. After this post I may consider modify mine a little and move the ball a little closer to the fender. Do to the way the side pieces are attached there should never be any twisting of the main hitch frame that I built. It is all made of 304 stainless steel. The side straps go up to bolts on the back of the frame and the horizontal straps go to an existing bolt hole on the side of the tire just in front of the center point of the tire. I attached pictures of the back view without the fender on. I had to bolt together the lower parts so if I ever had to remove it, it wouldn't be a PITA by having to go to the upper strap connection points to remove.
Any design improvements are welcome.
 

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#40 ·
Thanks Tom for sharing. Great explanations with example videos. Mark in Tucson

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