Bouncy utility trailer for carrying bycicles.

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Bouncy utility trailer for carrying bycicles.

Postby MacTrac » Sat Aug 01, 2009 7:44 pm

Hi, I am new here with a problem that I can't figure out.

I use a small utility trailer for carrying bicycles. I estimate that bikes, spare tire, plywood deck are less than 200lb (may be 150lb??)

Here is a link for the trailer kit I use:
http://www.harborfreight.com/cpi/ctaf/D ... mber=90153

It uses slipper springs, originally 3 leafs. I removed 2 smaller leafs on each side and inflated tires to 9 PSI to reduce trailer's bouncing.

It still bounces like crazy and cars behind me keep a distance afraid of a bike felling down. On smooth roads it rides like a dream.

Is there a solution?

Thank you!
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Postby kennyrayandersen » Sun Aug 02, 2009 4:15 am

Sure, there is always a solution, but first you have to define the problem!

You problem is that you basically have zero payload, but springs set up for several hundred. Unless you are hauling a couple of commie pigs-to-market bikes, you are haling maybe 50-100 pounds. The trailer was originally rated for 1000 lb, but you removed a couple of springs, so maybe now 400 lb?


Your second problem is that the leaf spring-type suspension setups have little damping. Andrew says 10%, which doesn't seem unreasonable.


So, you have to likely solve both these problem to get satisfactory results. If you can find a weaker spring, that would probably help with the first. Mind you, you would be able to use the trailer for hauling much more than bikes... but that appears to be at least a big reason why you got it. Second, you'll need to find some dampers (shocks), but the problem there is finding something light duty enough -- maybe something off an old moped might work?
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Postby MacTrac » Sun Aug 02, 2009 10:12 am

I got the trailer to haul 4 bikes with our family car. However, there were few more options but the utility trailer seemed the best one (now I am not totally sure about my choice):

- get a roof rack
- get a SUV with a large capacity hitch bicycle rack
- get a $2500 specialty trailer
- get a utility trailer

I was looking for weaker springs but no success, I will keep looking. Finding dampers and implement them is not going to be easy either.

I was also thinking about grinding the middle of the original spring out. The spring is 2" wide and 20.5" long (from the eye to the "eye" (the slipper section)). I am afraid that heat generated would change material's property.
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Postby MacTrac » Sun Aug 02, 2009 5:29 pm

I think most importantly the spring is too stiff. When I said bouncing, I should say, the suspension is too stiff instead.


Still looking no luck... :( I doubt there are spring's rated for my purpose. Right/wrong? I was also thinking to drill bunch of holes into them but is that going to help? How hard is it going to be to drill bunch of holes? I think too hard...


What about this product? Is it rated for my purpose? Would it solve the issue?

http://www.northerntool.com/webapp/wcs/ ... _200335740
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Postby kennyrayandersen » Sun Aug 02, 2009 6:44 pm

MacTrac wrote:I think most importantly the spring is too stiff. When I said bouncing, I should say, the suspension is too stiff instead.


Still looking no luck... :( I doubt there are spring's rated for my purpose. Right/wrong? I was also thinking to drill bunch of holes into them but is that going to help? How hard is it going to be to drill bunch of holes? I think too hard...


What about this product? Is it rated for my purpose? Would it solve the issue?

http://www.northerntool.com/webapp/wcs/ ... _200335740


I think even those might be too stiff; though, you might be able to get a trailer joint to de-rate them (or ones that they carry -- those don't look like they can be opened up to modify) a bit for your application. I think the 425-500 lb torsion axles are for jet skis and what not -- you have even less weight than that! Four bikes are going to weigh no more than 120 lb unless you are a maniac down-hiller. Even if you throw a gear box on there you are up to what, 200? I makes me wonder whether you need to do your own suspension with some motorcycle coil-overs.

Then again, if you put a gear box on there, include the frame in the weight and always carry all the bikes, it might work (but I've seen them down to 425 lb, which I would look for).

I can't remember where I saw the 425 lb torsion axle, a quick look through the data I gathered listed:

Dexter: 600lb
Flexride: 550 lb
Al-Ko: 500 lb

Hopefully someone else will chime in with a lighter torsion axle source.

This guy built one using Northern Tool parts that was pretty light -- you could probably get some ideas from his build although yours will obviously be a bit different:
http://www1.cedar-rapids.net/tdkmotor/s ... ailer.html
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Postby Steve_Cox » Sun Aug 02, 2009 7:00 pm

How about a couple hundred pounds of lead bolted onto the frame? That would smooth the ride out.
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Postby MacTrac » Sun Aug 02, 2009 7:19 pm

Thanks for all the help!

I placed a scale under each wheel and the tongue of the loaded trailer. Here are the 3 measurements:

120lb, 125lb, 35lb = 280 lb.

That is for the trailer with wheels, 4 bikes (with front wheels removed), deck made of a plywood and a spare. It is way less than I thought.

They state the shipping weight as 157 lbs so 280 lb is reasonable.


"How about a couple hundred pounds of lead bolted onto the frame? That would smooth the ride out." I am sure of that but is not good for the environment (increased MPG). :)
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Postby MacTrac » Sun Aug 02, 2009 7:38 pm

kennyrayandersen wrote:This guy built one using Northern Tool parts that was pretty light -- you could probably get some ideas from his build although yours will obviously be a bit different:
http://www1.cedar-rapids.net/tdkmotor/s ... ailer.html


Actually, he is using a Torsion Axle sold by Northern Tool:

http://www.northerntool.com/webapp/wcs/ ... _200335740

He says: "Torsion box part# 224222"

Also he states: "All the other gear is in the trailer with a final weight of approx. #340lbs." Which is not too far from 280 lb I have.

I think this setup should work???
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Postby kennyrayandersen » Sun Aug 02, 2009 11:25 pm

MacTrac wrote:
kennyrayandersen wrote:This guy built one using Northern Tool parts that was pretty light -- you could probably get some ideas from his build although yours will obviously be a bit different:
http://www1.cedar-rapids.net/tdkmotor/s ... ailer.html


Actually, he is using a Torsion Axle sold by Northern Tool:

http://www.northerntool.com/webapp/wcs/ ... _200335740

He says: "Torsion box part# 224222"

Also he states: "All the other gear is in the trailer with a final weight of approx. #340lbs." Which is not too far from 280 lb I have.

I think this setup should work???



It's not that far off. Your frame is really heavier than you need for doing what you are doing, but since you have it there is no need to chuck it. It think you are seeing though, that in the end, it's just better to build what you need from scratch.

Northern Tool doesn't actually make anything, so someone is making their axles for them and it does match the load rating on the Al-Ko, but I don't know for sure if they are the ones making it. It would probably work better than what you got, but it might be worth stopping buy or calling a local trailer manufacturer (every decent sized city has one) and ask about getting the axles de-rated (they remove a bit of the rubber out of the axle so that it carries less load. as 280 is just a bit more than half the axle rating. Some guys have suggested over rating them by 20-30% which would be about 350 -- not NO much under 500 lb, but a fair amount. If you could find the 425 lb axles it might be even better, but I sorry that I can't seem to find where I saw them (it may be that some article I was reading where they had been de-rated to that).
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Postby MacTrac » Mon Aug 03, 2009 12:02 am

Great info! I will call local guys tomorrow...

I googled it and this is what I found:

http://www.southwestwheel.com/store/p-3 ... axles.aspx

http://www.amazon.com/Capacity-Adjustab ... B001P95QFY

Is this the product you meant?
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Postby kennyrayandersen » Mon Aug 03, 2009 1:03 am

MacTrac wrote:Great info! I will call local guys tomorrow...

I googled it and this is what I found:

http://www.southwestwheel.com/store/p-3 ... axles.aspx

http://www.amazon.com/Capacity-Adjustab ... B001P95QFY

Is this the product you meant?


YEAH! that's it -- SW Wheel is in Arlington, which is right next to Ft. Worth (I'm a bit west of Ft. Worth) -- I'm sure I looked at there site and that's where I saw it. Maybe not a big deal, but closer to what you are looking for -- should ride nice! :thumbsup:
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Postby MacTrac » Mon Aug 03, 2009 10:07 pm

Here is a link for a picture showing how it looks from the bottom (click on the magnifying glass, top right corner, for more detailed view).

http://picasaweb.google.com/macmedo/Tra ... 4349141026

The white strip there indicates where the axle was originally.

If I mount the body of the axle on the middle beam, the axle should be not too far from the original axle position. Would that be OK or there is a better place for the axle?

Here is a detail (in scale as much as possible :) ):

http://picasaweb.google.com/macmedo/Tra ... 8923064130

It shows the axle mounted on a piece of a sheet metal. Is this a good implementation?
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Postby kennyrayandersen » Tue Aug 04, 2009 6:53 pm

Since your trailer is so light, I wouldn’t suspect that the axle location was too critical – obviously you don’t want it so far forward that the coupler pulls up! If it was balanced before the way you wanted it, then the new axle should go in the same location as the old one. Note I didn’t say the fitting, but the axle – that where the load balances (not at the fitting). My guess is the fitting should be pretty close [when it’s all said and done] to that cross member (which is a good thing). The cross member will help react the moment caused from the tires being outboard of the fitting mount.
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