bicycle trailer question

[Lunchbox7985]

so while im not even done with my chuck wagon yet, ive started another small project (by the way, that sentence pretty much describes me). So im building this little 4x2 trailer for my bike. my main purpose if to use it to tow the 30" storage trunk i keep my telescope in, but i may eventually use it to get groceries, as the store is only about 2.5 miles away.

now i realize that anything i do to this little thing is going to have about 1/10 the effect of stuff you guys do to your travel trailers, but i figure i may as well ask this. I'm thinking about getting these little 10 inch tires from harbor freight, the kind you would put on a wheel barrow, or a dolly. and just mounting the axle straight to the frame (A) . vs building something that raises the frame off the axle a bit like a suspension system would (B)

a.jpg (29.08 KiB) Viewed 1489 times

now for such a light duty trailer i think any sort of suspension (while cool) would be major overkill, so this would just be a little extension to change the center of gravity. but im not sure exactly what this would achieve. obviously a higher center of gravity would increase the chance of rollover, but thats not a concern here. im just having a hard time thinking about what all this would affect. besides ground clearance, and approach and departure angle, but for a bicycle, i dont think either of these are issues.

are there any other factors that i might consider that im not thinking of?


thanks as always
Brandon

[Lunchbox7985]

also disregard the horizontal axle placment on that pic, i realize i will want the axle offset toward the back a little. the pic was just a quick mock to show what i was trying to get across. again, i doubt i will load the thing up with enough to really have to worry about front to back distribution.

[Glenn Butcher]

We lived for a couple of years on Kwajalein island, where bicycle transportation is the thing. Out there, you needed a bike trailer of some sort to get through the day's errands; most folk bought a Burley (spelling?), but some built their own for various reasons. Most of the home-builts used bicycle wheels, and my thinking there vs the HF wheels would be that the rolling resistance would be greater with the wider and smaller-diameter wheels. This is just blind intuition, someone with actual experience should pipe in here.

Probably your biggest challenge will be a decent coupling mechanism. On the island, some folks just tied their creation via whatever tongue they fabricated to some part of the bike with twine or rope, but I'm guessing you will want a less rube-Goldberg solution. The best way IMHO for a heavy trailer to be attached to a bicycle would be through a tongue that curved up to just behind the seat, mounted to a pivot point supported by either the seat post or a bike rack mounted to the seat post. Just like with a car-pulled trailer, you need to worry not only getting the thing going, but stopping it as well.

[fotooutdoors]

Personally, I would stick with bike wheels, and go larger diameter. Larger wheels are less effected by bumps and cracks; if you think of a pothole, a small wheel can actually fall into it, but a larger wheel will only partially fall into it.

I would certainly not elevate the body unless you are using suspension; some child trailers have suspension, so it isn't crazy to consider, though it adds considerable complexity to what is a fairly simple project. I have made a couple trailers, but none with suspension.

If you want to see a number of home made trailers, check out the utility board on bikeforums.net and the cargo bike board on forums.mtbr.com

[Lunchbox7985]

those are good points, I wanted bike wheels, but the HF ones are cheap and available. I may just have to be patient and try to find a cheap/free bike on craigslist.

I really want to go with hooking it to the rear axle of the bike, as Ive read that makes it more stable, I can see how a seat post mount would increase maneuverability, but I think on the cheap, I can make something stronger going this way.

and as far as the hitch, I found some absolute genius whos idea im stealing.



air coupler bolted to a caster.

[Lunchbox7985]

thanks for the other sites, guess I should have looked there first. I really have to stop thinking my ideas are so original .

guess a lot of people have pretty low sitting trailers, with the axle only an inch or so offset from the flat part. must work pretty well for them.

im gonna stop by harbor freight after work and look at those wheels, for what im doing they may be good enough, if not, ill start combing craigslist for a cheap kids bike.

[KCStudly]

Northern Tool has some lighter weight, larger spoked wheel/tire combos: http://www.northerntool.com/shop/tools/category_tires-wheels+spoked-wheels+flat-free-spoked-wheels

I wonder how that air chuck hitch does in a right hand turn. What keeps the tongue from contacting the tire?

[fotooutdoors]

I am a fan of the hitch at the rear dropout...much better stability if you are carrying a heavy load.

Nothing keeps you from hitting the tongue with the tire if you take more than a roughly 45° turn. That said, I challenge you to go take that tight of a turn while pulling a load. It just doesn't happen. Backing the trailer and bike combo out of a tight space? Yep, then it will, but you can just lift the bike to reposition.

I have hundreds, if not thousands, of miles and hundreds of trips pulling a cart behind my bike. Because light weight is so important (you can pick up a bike trailer), simplicity is one of the most important design parameters.

[Glenn Butcher]

Northern Tool has some lighter weight, larger spoked wheel/tire combos: http://www.northerntool.com/shop/tools/category_tires-wheels+spoked-wheels+flat-free-spoked-wheels

I wonder how that air chuck hitch does in a right hand turn. What keeps the tongue from contacting the tire?

Google "burley trailer", the tongue extends forward from the left-hand side of the trailer, then angles in to the coupler.

The air hose coupler is interesting, but I'd worry about stresses sufficient to pop it apart... Consider turning the caster 90 degrees so the holes line up vertically, then use a 'drop pin'' on the tongue, probably with a clevis pin to keep it from pulling out.

[fotooutdoors]

One other option is a ball end joint. They run about $5 on Amazon. Then you just need some c channel or even better, an f profile, to attach to your rear axle. Check out how a Burley attaches; this is the same concept, but using a metal connection instead of a flex rubber.

[Lunchbox7985]

thhought you guys might want to see it.







that closeup of the hitch was just after a ride, and i snapped the pic really quick but didnt notice that it had started to come loose, once i tightened it the air coupler sits more or less level, and parallel to the bike. i have also added more reinforcment to the tounge.

i decided to just mount the axle straight to the trailer for simplicity. and while the hitch is lower than the axle of the bike, since its even horizontally with the axel, even if the bike is going up a hill or something the hitch doesnt dip as it would in a car.

i just bought the parts to put together the walls of it, i plan on doing it tomorow so hopefully ill get some pics then or the next day or so.

[Lunchbox7985]

Glenn, im thinking you thought the first pic i posted was how it sat, hopefully the pic of mine clears it up. that first pic, it was hanging since nothing was hooked to it, but you see with mine, how it sits like i think you were suggesting (other than the fact that one screw is loose and it sagging in the pic).

i wanted to use the coupler instead of just a clevis pin to add a third axis of movement, the caster allows side to side and up and down, but the air coupler allows it to twist as well. probably not needed, but if i really lean into a turn it may come in handy

and as fotooutdoors said, you have to really turn hard to get the tire to rub the tounge, i can do it, but i have to be going so slow to turn that sharp that its not a big deal. leave a little black mark on the tounge, but im not going fast enough for it to really hur anything.

[Lunchbox7985]

here we go.







no the snow sled is not a permanent solution. i just sold my jeep, my wife has the car at work, and i really wanted to go somewhere, so ingenuity happened .

Plus the other bike thats in better shape, and that i put road tires on (OMG what a difference)

also a picture of the hitch with the screw tightened, it did come loose again after about 2 miles and i left my son about 5 feet behind me on the sidewalk. no harm done, it just skidded to a stop on the tounge. it came loost as the trailer wheels hit the little 1 inch of a curb on the ramp for the sidewalk, so i was barely moving. i need to go get a lock washer for that particular screw.

anyway, thats it for now on the trailer, my riser handlebars got delivered while i was out, so im gonna rest and go swap those out.

[KCStudly]

The problem with the screw looks to be that it is self loosening when you turn. You could either run a longer bolt with jam nuts top and bottom of the tongue (so that the shank part of the bolt has a little play for the air chuck, but the bolt stays tight), or you could add another tab off of your tongue stiffener and put the bolt in double shear.

[Lunchbox7985]

honestly i was thinking a little lower tech of lock washer and then covering the end of the tounge in some epoxy like jb weld.

ya, it needs a little attention, i want that part of the coupler to be rigid so that the turning is handled by the other side. and as you can see ive got a double nut going on so the bolt stays tightn but the coupler can turn freely.

but like you said, when i turn, the male side of the coupler wants to be at the same angle as the tongue, where i want it to be parallel to the bike (even though it probably doesnt matter) either way it does need to be rigid, but i think i could just fil the area around the chuck up to the tongue stifiner with jb weld and it would be fine, it doesnt seem to have a lot of pressure on it with how freely the other end swivels, so it wouldnt take much.