Is there a Mechanical Engineer in the house? - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
General V-Strom Discussion Talk about all things V-Strom not limited to just one of the above models

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post #1 of 36 Old 08-03-2012, 05:24 PM Thread Starter
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Is there a Mechanical Engineer in the house?

Can anyone tell me why this trailer tail whips and wobbles? I have tried pulluing it empty and with about 40lbs on it. The tire is a worn out dirt bike tire I haven't purchased the new one yet because I want to make sure the thing is going to work. There is a link to more detailed pictures under the image.


Motorcycle Trailer pictures by surveywaters - Photobucket
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post #2 of 36 Old 08-03-2012, 05:34 PM
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I'm not an engineer but I can tell you one thing, the attachment to the bike is way too high. It should be about axle level.

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post #3 of 36 Old 08-03-2012, 05:56 PM
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Greywolf is right have a look at this
moto-mule a cargo trailer to pull behind your dual sport motorcycle - ADVrider
and this
Trailer hitch on a GSA? - ADVrider
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Learnt to ride on - Suzuki 80 -1969
[B]Bikes I have owned[/B] * CZ 175 * Yamaha DT250a * Honda CB450 * Kawa KL250 * Honda CB750F2 * Honda CR250m2 * Suzuki DR250 * Yamaha TX650a * Honda SL350 And Kawa KE175 * Honda CX500ec (Had it 16 Yrs, Wrecked by car turning in front of me) * BMW K100rs 1991
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post #4 of 36 Old 08-03-2012, 06:09 PM Thread Starter
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Those are great although having a hitch unsprung like the one going through the axle is a terrible idea.

Now have a look at this. It wasn't my idea, I'm just to cheap to buy the tested one.
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post #5 of 36 Old 08-03-2012, 06:14 PM
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Are those shocks loaded enough, and are they damping at all?

Static sag should be about 1/4-1/3 travel, or you're gonna have a bad time since the tire is only going to spend a small portion of the time on the ground.

Also, the rear section (the ladder-like bits) need some bracing to the, um... downtube(?) or it's just going to pivot around the swingarm.

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post #6 of 36 Old 08-03-2012, 06:34 PM
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Quote:
Originally Posted by greywolf View Post
I'm not an engineer but I can tell you one thing, the attachment to the bike is way too high. It should be about axle level.
I am a mechanical engineer and GW is spot on. Lower your pull point. Good luck!

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post #7 of 36 Old 08-03-2012, 06:35 PM Thread Starter
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Now we're getting somewhere. The tire is not leaving the ground, the shocks are pretty supple and adjustable via multiple holes for the upper mount. Would you expand on the pivot action that is mentioned? That is what's going on and I can't place where it's coming from. The section above the tire starts swaying and then the tail starts to whip violently as this swaying accelerates.
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post #8 of 36 Old 08-03-2012, 07:09 PM
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The reason everyone is right that says the attachment point for the trailer is to high is because the left and right movement is twice as more then if it was attached at the rear tire axel height. The movement is steering the trailer wheel causing it to sway. The sway is causing the bike to lean left and right. The trailer is counter weighting the bike so it will still track staight. The trailer will never be controllable mounted that high.
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post #9 of 36 Old 08-03-2012, 07:10 PM
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I'm and ME as well. I agree with the connection point to the bike being too high. Another consideration is if the entire structure is square. With a high hitch point, any out-of-square welds or a slightly out-of-true axel will amplify lateral stability issues.

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post #10 of 36 Old 08-03-2012, 07:11 PM Thread Starter
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Quote:
Originally Posted by bassbronco_74 View Post
I am a mechanical engineer and GW is spot on. Lower your pull point. Good luck!
If this is the problem then Eaglemate is selling a product that does not function as described...not only that but dangerous. I have not read any reports of this though. I understand the trepidations around a high hitch point, mainly the torque values on the upper portion of the bike either pulling you over, making it difficult to upright, or pulling the bike sideways in a turn. I do not see any of these causing the trailer to sway though.

If when you say the hitch point is to high you are basing this off of some reverse rake/trail or something related to the length and angle of the trailer, I would be open to hearing that explanation.
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