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Trailer construction ideas, design

Old 10-29-20, 02:10 PM
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Trailer construction ideas, design

All,

After a 12 day trek with my Disk Trucker + panniers and dry sacks I am looking in to making a trailer. I met a fellow tourer on my travels that uses a trailer and spent 3 days with him on the trail. Between hauling gear the way I was and resupplying on the trip I think the trailer idea makes more sense. It is less load on the bike frame, lower center of gravity, and easier to balance on the bike. Weight is weight, I realize - especially going up hills. So no matter where the weight is it is something that has to be dealt with, however the extra wheels offer a big benefit to how the load is supported - more axles to distribute the weight over.

A few questions/topics -

1. I have seen a ton of creative ways of making hitches - from castor wheel frames to universal joints to simple eye bolts and pins. My first thought was to use a ball joint threaded rod end - the plain kind with a simple hole in the ball portion - and a pin sandwiched between two metal tabs. However, this might be too limited in the roll direction. The trailer the guy I rode with used a Burly hitch - the bar on the trailer up to the mounting bracket on the bike. That hitch uses a rubber part that flexes at the bike end of the hitch bar. I am not sure I like that style, but there might be some merit to the flexibility of the rubber - it would keep the vibration/shock transfer down from the trailer to the bike. I'd like to have something that won't rattle much and won't woller out with wear like a lawn tractor pin style hitch but also something that is quick to release with a pin as opposed to a bolt/nut.

2. Wheels. I am thinking 26" as it would roll easier over bumps. However, 20" is pretty common. BMX style wheels that are beefy and built for jumping ramps would probably be stronger than most other types of wheels. I remember in my BMX days about 15 years ago one of the big upgrades was Alex triple wall rims. The triple wall meaning 3 levels of structure in the direction of the spokes (and tall side walls where the brake pads would go). They were heavier, but guys that switched to them had a lot less rim problems. As to hubs - I am sure there is something out there that has a beefy axle/bearing set up. I am not sure what is more important - a beefy hub/bearing/axle assembly or a beefy rim. Both are important, I suppose. I would imagine there are some strong options in 26", but I doubt that category of rim would be as strong as the severe duty of the triple wall 20" BMX rims. My goal would be a wheel set that I don't have to worry about loading or hitting bumps with. I don't intend to be hauling 500lbs, but if I'm between 100-200 over a lot of miles I'd rather steer clear of the department store type kids 20" bike wheels/axles/hubs.

Another note on wheels is the trailer the guy had that I hung out with had an outside rail on each side with the wheel axles supported on both sides. This makes a whole lot of sense, as opposed to the axle only being held from the one side closest to the trailer frame. The rails on his design used all-thread rod so as where adjustable to different axle widths. I am not sure that I would want to plan on different axle widths, but the outside rail to support the axle from both sides, from a loading perspective (and.... damage control - the rails would act like a bumper/rub rail to protect the wheels and axles from damage) is a great idea.

3. Material. I know aluminum is lighter than steel, but it scares me a bit. I'd prefer to weld the frame together. Steel is way easier - and also easier to repair on-the-go if need-be. With regards to aluminum - is there an aluminum that is easier to stick weld? That is the only way I can weld aluminum - no mig or tig here, and it would be easy to stash a few aluminum rods for a fix on-the-go at a farm or service shop somewhere that had a DC stick machine. Otherwise, I think steel would be the least hassle. As to what grade - not sure. All the steel I've worked with has been A36 over the years, standard structural steel. I have a light flux core machine also, but with the stick I have a lot more flexibility (rod types/sizes, variable polarity, amperage, etc, etc). I suppose I could O/A a frame together also... but it would be a lot cheaper running stick as I'd have to get bigger bottles + the gas and maybe fitting adapters and that would be $300-500, vs maybe a box or two of a certain rod (have a bunch including Crown Alloys Royal 300's - 3/16" - for aluminum).

4. Size. Dealing with trails and people I don't think it is wise to go very wide. My bike with all the bags on it was too wide for my liking as it was. I'm thinking maybe of staying under 30", maybe 22-24" for the cargo box plus the wheels/framing outside of it? As far as length goes - I am going to set all my gear out and sort it to see what fits in that 22-24" width and see how long that gets. Figure that is a starting point for volume. Something that bothered me on my trek was resupplying and tossing all the bags on top without being able to get that stuff down inside the bags I had, for the most part. If I have more than enough space inside the trailer for all my gear then I have room for those resupply runs and getting that stuff inside the trailer. Yeah, adding weight isn't always a good thing - but by having the ability to resupply with a good amount of stuff that will open up how far I can go between resupply runs and ease up on stuff to get me by a period of sitting for a few days - water, food, fuel.
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Old 10-30-20, 11:51 AM
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I am working up a post-trip video on gear and the trip. So I laid out all my gear - I have not unpacked much at all from the trip. This is a good gauge to the space I want. Of course, with the bags there is a lot of dead space between that adds lot to the overall volume here - so the actual gear volume is a lot less. However, I'd rather have space and not need it than to not have space and end up tieing stuff on the outside.

Another thought is organization. With space available compartmentalizing is a reality. I can put my food and water in the middle over the axle, for example, and section off the front and back for other gear. That way the heavy stuff (water and canned foods) are closest to the axle and all together, unless I need to move weight for balancing then moving water bottles fore/aft is easy ballast.

From the split in the concrete to the rake handle is 4 feet. If I make the box inside dimensions 24" x 24" x 48" that will fit what you see here with room to spare. That is the stuff in the bags to boot, not split out of the bags. So volume-wise the dimensions here may have my gear taking up about 75% of it. If I add another foot and stretch the box to 5 feet/60" that would give me a ton more space. I am not sure that I want that much, but I will mull it over. At 4 feet looking at the layout of the gear I am sure that would give me plenty to work with, but the builder and packer in me says go bigger.

Maybe a design that allows me to stretch the trailer and add more space if needed is on order. That sounds like a better plan - in the summer time Id probably have less gear so it wouldnt make sense to only fill the trailer 1/4 full. Or at that point I could forego the trailer all together and go panniers only. Lotsa options.


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Old 10-30-20, 12:17 PM
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I'm interested to see what you end up with. Is it worth looking at some of the proven existing trailer styles/designs as a template? You know, not reinvent the wheel (pun intended)?
Here's the BOB; https://www.bobgear.com/yak-bike-trailer
At 17" wide and 64" long, it seems to hit your size needs.
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Old 10-30-20, 03:58 PM
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Originally Posted by bOsscO View Post
Is it worth looking at some of the proven existing trailer styles/designs as a template? You know, not reinvent the wheel (pun intended)?
Here's the BOB; https://www.bobgear.com/yak-bike-trailer
At 17" wide and 64" long, it seems to hit your size needs.
Thanks for the thought.

I have looked at a lot of bike trailers. What the commercial options tend to cater to is what is more normal/what the market will more largely accept. The BOB is quite popular as you note. However, it is a single wheel design and I want to try a dual wheel design. I also want a dry box design and not an open frame where dry bags (like I am using now) are set and strapped in. I'd like to be able to open the lid and access my stuff.

To that point - that is where compartmentalizing would really be nice. That and the idea of plenty of space inside so as to never need to strap things (generally speaking) to the outside of the trailer box. If the lid on top is what opens and I need to strap stuff to the top of it then to access the stuff inside the trailer it requires unstrapping and removing the stuff on top to open the trailer lid. I don't want that fiasco.

There will always be some gear on the bike - namely the handlebar bag. I never ride without the handlebar bag as that is where I put tools also. On shorter rides I pack everything in to it - spare tube, tools, first aid, snacks, etc. On longer rides/trips I spread the tools out between the hanldebar bag and panniers. With a trailer I would keep only routine stuff in the handlebar bag (allen wrench set, for example) then other tools/supplies in the trailer. If I had a flat, for example, I would want to be able to easily open the trailer lid to access the rest of the tools, pump, and tube. I think it might even be handy to mount some of that stuff in a box on the lid perhaps.

Maybe having multiple lids would be good. Maybe 3 sections - fore, mid, and aft - with their own lids.

I think no matter what I do I will make the trailer somewhat sectional so I can add to it. I am not sure how to do it just yet. I want the axle more in the middle and if I only add on to the front or rear then the axle position gets skewed. Adding to the front would make the most sense of the two, however the extra long portion ahead of the axle means as weight is added to the trailer the tongue will get heavier. That is the idea of the axle more in the middle - it is easier to get the balance right and keep the weight centered on the trailer.

I am sure some experimentation is on order for tongue weight vs tracking stability and ride stability on the bike, but with regards to bumper pull trailers on cars and pickups the rule of thumb is 10-15% gross trailer weight on the tongue. So if you have a 10,000lb trailer then 1000-1500lbs is your tongue weight. Gooseneck and 5th wheel trailers that % goes up to 25%. So for a 14,000lb 5th wheel, for example, 3500lbs is the pin weight. Of the two examples - bumper pull is the closest that equates to a bike trailer pulled with a hitch at the axle I would think. A hitch up by the seat post might equate more to a gooseneck/5th wheel set up, however being a 2 wheel cycle that leans in turns I am not sure how the weight distribution would actually work. And that is why my design would be an axle hitch design - not a seat post hitch. The pushing and pulling the trailer would do to the bike should be less at the axle than the seat post = better ride and easier to balance I'd say.
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Old 10-31-20, 10:33 PM
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Originally Posted by KC8QVO View Post
1. I have seen a ton of creative ways of making hitches - from castor wheel frames to universal joints to simple eye bolts and pins. My first thought was to use a ball joint threaded rod end - the plain kind with a simple hole in the ball portion - and a pin sandwiched between two metal tabs. However, this might be too limited in the roll direction. The trailer the guy I rode with used a Burly hitch - the bar on the trailer up to the mounting bracket on the bike. That hitch uses a rubber part that flexes at the bike end of the hitch bar. I am not sure I like that style, but there might be some merit to the flexibility of the rubber - it would keep the vibration/shock transfer down from the trailer to the bike. I'd like to have something that won't rattle much and won't woller out with wear like a lawn tractor pin style hitch but also something that is quick to release with a pin as opposed to a bolt/nut.
The Bikes At Work side mount/axle hitch looks pretty promising. This one uses the same plain rod end ball joint I was referring to. From the pictures on the site it appears to use a lock nut and is mounted in a round tube. My assumption is if the trailer rolled beyond a certain angle the ball joint frame (the threaded part and lollipop head) would rotate inside the tube. That would certainly overcome the roll issue with the give in how the ball joint is attached.

https://www.bikesatwork.com/store/pr...-trailer-hitch
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Old 11-02-20, 02:44 PM
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Originally Posted by KC8QVO View Post
The Bikes At Work side mount/axle hitch looks pretty promising. This one uses the same plain rod end ball joint I was referring to. From the pictures on the site it appears to use a lock nut and is mounted in a round tube. My assumption is if the trailer rolled beyond a certain angle the ball joint frame (the threaded part and lollipop head) would rotate inside the tube. That would certainly overcome the roll issue with the give in how the ball joint is attached.

https://www.bikesatwork.com/store/pr...-trailer-hitch
This is a hitch I made years ago. It's a bit crude but works OK, never had any problems. The part that goes on the bike was modified after the first ride to keep it aligned.




I used wheelchair hubs, 12mm axles and ball bearings are enough up to 50-60 kilos IMO.
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Old 11-02-20, 02:55 PM
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Old 11-02-20, 04:20 PM
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Originally Posted by Reynolds View Post
This is a hitch I made years ago. It's a bit crude but works OK, never had any problems.
Thanks for the pictures.

It looks like the part I am looking for is called a "heim joint". Below is a link to an example. I will dig around and see if I can find less expensive option. I suppose at the start it doesn't necessarily need to be that, but I think it is a good solution. Stainless so the joint doesnt seize with rust (plus keep it lubricated).

https://www.speedwaymotors.com/FK-Ro...int,81626.html

I like the Bikes At Work framing with the aluminum C channel construction. The trailer in the following link is similar in design - C channel - and welded. I think that is what I want to do for the base. I like the front and rear C channel members, as opposed to the rectangular tubing of the Bikes At Work designs.

https://www.flickr.com/photos/monkey...7617446793100/

The electrodes I have, and can get pretty easy, for aluminum are Crown Alloys Royal 300. I contacted Crown to find what grades the rods work best with and they are confident in them with any "weldable" aluminum (that is a weird term because aluminum is a weird metal - there are some aluminums that just plain cant be welded with any conventional process). That having been said - there is a place around here a buddy of mine gets alloys from. I will come up with a rough design then check with them and see what I can source and pricing. I know my buddy gets small quantities of bars, billets, and sheet/plate of various aluminums so I would think more structural stuff would be pretty easy to get. I'm thinking 6061-T6, but that will depend on pricing and if there is an adequate C channel extrusion in that grade. 6061-T6 is plenty weldable.

The other option is chromoly steel, though that would boost the weight a bit I think.

As for the cargo box - I am not real sure how to do that. I had the thought of using Coroplast. However, it would need angle alum or steel on the edges for strength and protection. At that rate it might work out to use sheet alum if I can get it for a decent price. With the flat C channel frame having a base for the box would be pretty easy. Bolting the box to the frame would make it easy to remove the box and turn it in to a deck/flatbed cargo trailer also.
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Old 11-04-20, 05:27 PM
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As far as aluminum goes - it looks like 6063 is going to be easier to source from the "architectural metals" category, as opposed to "structural".

I really like the frame construction technique - just the outside rectangle with the C channel - of this build:
https://www.flickr.com/photos/monkey...7617446793100/

However, I think the frame might actually be too beefy for what I am thinking.

If you think about the whole assembly - the box on frame - the frame is adding rigidity to the floor of the box. So both the frame and the box work together to distribute the load. The flat flanges of the C channel make for a convenient way of attaching the box to the frame, as well as the other structural members that take more concentrated loads - such as where the wheels (axles) attach and the hitch bar. Therefore, the thickness and, ultimately, weight of the frame material can be less. Sorta like a unibody car that doesn't have a body-on-frame like a truck or SUV.

The overall idea is to have a lighter weight trailer than would be achievable with a steel frame that is still durable enough to pack the miles. I am hoping the completed rolling weight of the trailer + gear is at most 200lbs. Figure 150lbs gear and a 50lb allowance for the complete trailer, just for rough numbers.

The Bikes At Work 64A comes in at about 38lbs. Size-wise that is similar. So I am hoping that the 50lb allowance for the trailer is realistic - adding a box and maybe thinning down the material around the frame/cross bars by having the box there.
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