I am thinking of a 6.5hp rear drive.

[bike4life]

View attachment 86963
without getting into hairy geometry, a couple principles show up just seeing the angles. I found the longer the tongue, reduces the pivot angle. perfection in turns would be an infinitely long tongue, catastrophic failure is a certainty at pivot angle above 90 degrees. to scale, this is a 3 x 2 trailer with tongue 1/2 of trailer length. you can see the angle is ~75deg. already approaching a bad situation lol (15 deg steering input and you're in trouble at a moderate slow speed.)
juggling some vectors, I see best is actually no pivot from the top looking down! you don't want a trailer 8' behind you, you'd like it close as you can get, like 6" or less from your back tire. at any length of tongue this'd make a really big pivot angle, so we remove the pivot and the trailer can only steer you through your handlebars, which you have control, and this makes the lever arm of any torque from engine very long, and gentle for you to control, regardless if it's 1.5hp or 6.5 haha.
with 1 dimensional hitch (vertical movement only), the tongue length is from handlebar stem to the drive axle. comfortably long, simplest design. add a flexible hitch like a ball, and the force vectors multiply the uncomfy steering torque and possible jackknife situations are there @ any tongue length less than 1/2.

so the simplest connection to the bike is solid, but up/down movement is good and safe. 1 horizontal bolt to the trailer
1 drive wheel or 2 makes no difference in this model

ok so heres what i can do.... when i built the hitch, i designed it for 2 axis. My trailer length is 35". So what do u think i should do, add a stop block to the hitch so i cant exceed like 75 degrees or should i just weld the swing part shut as a solid entity. The question is would i actually be able to make turns without the hitch swing part. Like in trucks and stuff, i think they have a ball hitch? My trailer is 15" by 35" so if i have a tongue length of 1/2 or 17.5" that forms an acute triangle with sides 15" base w/ 17.5" height. Cut triangle in half to get right triangle. To find angle tan^-1(7.5/17.5) which is 23 degrees. 23*2=46 degree pivot angle because i cut it in half. Personally i am thinking of adding stop blocks to restrict the swing to 75 degrees. what do u think??

 

[JerboaJohn]

since you already have 2 axis, keep it bcs slow speed turning will b easier. just to be safe, limit swing to something like 60 deg. if the turning radius is too big (like u gotta swing around in tighter than it lets u), you probably can cut the limiter a little, or grind down? I say 75 limit bcs if you are going more than ~15mph, 15 deg steering is pretty abrupt. faster than that, we lean more than turn the bars. you can't get into trouble below 10mph turning the bars like 20-30 deg. you'd put your foot down.
bcs it's one wheel, yeah I think you need a pivot. 2 wheels with one that turns free would do same thing but cost more to fab

ppl don't talk much about homemade bike trailers (esp. powered ones!) much so there's not much to go on. your experiences and pics can set a example to go by and improve on! maybe you'll be immortalized lol

 

[JerboaJohn]

good math! tho I calculate stuff, when you see it enough times, you can have an idea of angles. 90-(23)=67 and ball park close to what I conservatively thought is a safe limit angle. you're good to go
don't wanna get into load weight and momentum equations on turns esp when more variables like braking, accelerating from speed x
now you know why vehicle designers are a team and they all make big bucks, taking 2-3 years from scratch to build any vehicle!

 

[bike4life]

good math! tho I calculate stuff, when you see it enough times, you can have an idea of angles. 90-(23)=67 and ball park close to what I conservatively thought is a safe limit angle. you're good to go
don't wanna get into load weight and momentum equations on turns esp when more variables like braking, accelerating from speed x
now you know why vehicle designers are a team and they all make big bucks, taking 2-3 years from scratch to build any vehicle!

lol. yeah back in the day when i was younger, lol i am only 16 y do i talk like that?, i used to be a math geek tried to learn calc back in 8th grade and figured out half of the stuff. in 8th grade i was kinda fascinated when i cut out a parabolic shape on paper just for kicks and figured out its center of mass with a calc formula and then balanced it on a pencil and it matched the data from the formula. tho i was always viewed negatively for this and i gave up interest more or less. still believe that if u know the math and physics u can hack life. I still do well with math and visualize all the math/physics that i get at skool. I have a terrible memory like barely can remeber ppls names and what i ate or did an hour ago so i was forced to invent the equations or intuition instead of remebering them for tests and stuff. Tho its bad b/c i go to a medical highschool and we have anatomy physiology(instead of engineering and math stuff, 0 stem ciriculum) and medical terms in latin and i do terrible on them as medicine is straight up rote learning... btw the intention of this was not to brag just in case

I would hope they make big bucks... b/c otherwise college would be a waste of time, just join the trades or entrepreneurship. yeah unfortunately today i got sick so couldnt work on the pusher... maybe tommorow. I could just run a tongue length of 1/2 or 17.5" height which forms the 23" sides in the drawing and call 46 degrees safe but with a tongue length of 23", my bike wont fit on the train. Since i never buy a train ticket and just let them kick me off, i can go at least 7mi for free if they kick me off at the next stop or if i hide from them, maybe 15mi-20mi and then pusher bike the rest. plus the trains are fascinating, just watching the loco come in with the big traction motors and the fact that it can move hundreds of tons at a decent speed is crazy... i should probably get a job at the coney island rail yard in nyc which services the mta trains when the break down, tho i wonder if they pay ok.

 

[bike4life]

yo. #necromancer is here. im baaaackkk from vaction so stay tuuuuuuuuuned ??!! muchos gracios....

 

[bike4life]

reincarnate.

 

[bike4life]

Here it is. Deisign change. The pillow blocks have been moved to the bottom so the frame is higher off the ground when I install the tire.
The welds are stick and look good!!! A little wavy but it’s an ashetical thing.

 

[FNTPuck]

Cut a cross section of one of those welds man. Put two same size plates of the same exact metal into an "L" and weld along the joint then cut it in half and check for penetration and root gap.

It seems like it is allll on the surface, looks like virtually zero penetration. That won't hold much strength!

 

[bike4life]

Cut a cross section of one of those welds man. Put two same size plates of the same exact metal into an "L" and weld along the joint then cut it in half and check for penetration and root gap.

It seems like it is allll on the surface, looks like virtually zero penetration. That won't hold much strength!

i actually grinded in a bevel, i think it has penetration it was 6011. It was STICK. I am gonna put this on the welder forums and have them be the judge. https://weldingweb.com/newthread.php?do=newthread&f=6

 

[bike4life]

It seems like it is allll on the surface, looks like virtually zero penetration. That won't hold much strength!

I got the green light from the welders forum!!!! So no FTPUCK, it will hold. The link is in the previous post.