Senior Design: Design and Build a Trailer to be Pulled Behind a FZ6

[RJ2112]

My 2 cents, How would 150lbs pushing on the rear of the bike affect braking? I know it is a concern with pulling car trailers but smaller boat trailers have no adtional breaking system.

150lbs is @1/4 of the bike weight. I'd worry about jackknifing. May be way off but wanted to throw that out there JIC.

If the rider weighs 150 and has a 150 lb passenger, and 40 lbs of luggage on board, it's not so bad... I'm betting the braking system as installed is designed around at least that much of a combined vehicle weight.

My guess would be that it's very important how the tongue of the trailer is going to 'push' the chassis.... if it pushes the rear 'up' as you decellerate, could it unload the rear tire? If it pushed down, what would that do to chassis attitude?

I would personally want the force to pass as nearly as possible through the center of mass....

 

[FZ1inNH]

Yea i have been thinking about that. Not sure what do with it yet.... the way it is looking I might have to ditch the cooler completely. I hope not though.

Please don't! Here's a tip/disclaimer you can add. Whenever I travel with a cooler, I pack ice in QT ziplock bags. It keeps everything cold but also contains the water. In the event the cooler topples in the cage, there's no water spill, just pick up the bags and throw it all back in. This would also significantly reduce the motion by containing the water to smaller areas. OR, use the gel-pack freezer blocks.

 

[bmccrary]

Ok so I am going to try answer all these question in one post. Lets see how this goes, lol.

Hitch:
I am going to have the UJoint inline with the CG or below it, hopefully below it so that there is minimal effect when braking/accelerating. From there the trailer chassis will drop to like a minimal 8 inches off the ground. The lower the CG of the trailer the better. Right now I am fighting a frequency oscillation that would occur if I go into an evasive leaning maneuver. I think I have found a solution to this, but not 100% on that. I think I will have the two main chassis rails converge to one just before the ujoint instead of having one long bar going to the floor of the trailer. (if that makes since)

Braking issues:
Rule of thumb is that your braking distance doubles when you are pulling a trailer. You plan for it... you think you have to look far ahead now when riding a motorcycle now, try doubling it. Gotta be on your toes. That and you have to have the trailer inline with the motorcycle before you can brake.

BTW great tip on the ice in zip lock bags!

The floor of the trailer will be flat and the rear wheel will be at the end of the trailer. Nothing will be over the rear tire really, i mean the body will sorta cover it, but thats it.

As far as the rear wheel is concerned. I am going to use a 12" scooter wheel because most tire manufactures make their popular tires in those sizes. This will allow me to have matching tires! The dynamic side of the project will be tackled next week. I am going to start working on the motion ratios of the rear of the motorcycle in a bit. And compare that to the what the trailer should be.

Also I have to look into the "Decaster Effect" (spelling) essentially the trailer is a caster wheel... so with some detailed work (or so i have heard) I should be able to determine the max speed of the trailer.

-bryan

 

[RJ2112]

Thanks for sharing, Bryan.... it's fun to excercise the mind a bit with this...... especially as you're doing all the heavy lifting.

 

[bmccrary]

Thanks for sharing, Bryan.... it's fun to excercise the mind a bit with this...... especially as you're doing all the heavy lifting.

Indeed! Just have so much to do and calculate in minimal time. Does anyone know about bending square tubing? Is it doable, most machine shops capable of this? Looks as though I might be going to round tubing.

-bryan

 

[RJ2112]

Square tubing should bend as readily as round.... but not in as many directions. A 90° bend will have similar minimum radius, on the 'flats'; but it won't bend on the corners well at all.

 

[04fizzer]

Bryan, any chance you could post up a rough schematic of what you're doing (when you have time)? I'm having a difficult time visualizing what you're doing, and pictures work best for me in explaining (hey, I'm an engineer, it's what I work with all day).

 

[madmanmaigret]

This sounds pretty cool but way over my head! I did think that the freezer gel packs would be the way to go to keep water from sloshing but Eric beat me to it..... I will just crawl back in my cave now. :scared:

 

[bmccrary]

Bryan, any chance you could post up a rough schematic of what you're doing (when you have time)? I'm having a difficult time visualizing what you're doing, and pictures work best for me in explaining (hey, I'm an engineer, it's what I work with all day).

As soon as I get some models completed Ill post a few screen shots.

-bryan

 

[04fizzer]

As soon as I get some models completed Ill post a few screen shots.

-bryan

Good deal. I know you're busy (I've been in the same boat with school, so I know what you're going through), so don't worry until you've got time.

 

[bmccrary]

Ok so for Thanksgiving break, guess what I have been doing? Homework, homework and more homework and crap ton of senior design. Its been amazing! (sarcasm)

So any who, update.

I have ditched the idea about making my own body and all that. Instead, I am going to save time and money and buy a mobile toolbox from Lowes Home Improvement. In fact it is this one:
Stanley at Lowe's: Fat Max Portable Truck Box

I had to go to a smaller cooler to make this work, and I will have to strap the chairs and tent (all in storage bags) to the top of the box via a few well place eyelets. I had to redo several calculations, but thankfully I had converted all my mathCAD files into one large file so after a changing a few dimensions and noting the placement of the items everything this is hunky dory again. (sorta, im still pulling my hair out)

I then spent alot of time and I am still trying to figure out what wheel to run in the rear. Currently I am sold on a Kymco scooter front wheel, 3.00X12 as I can get various motorcycle tires for it and I might actually be able to use that scooters front axle as well...? (still working on that)

So then I spent some time working on the solid model and I just did a quick assembly to give you guys an idea of what I am doing. Note there will be a single shock mounted on that cross brace in the swing arm with the top mounting to the trailer where that major node is in the upright (or mid way up the handle of the dog sled, it seriously looks like a dog sled with a swing arm, doesn't it?)

There will be some sort of reducer that will take the square tube to round so I can bolt in my universal joint, there at the front. The weight is still unknown, sorta. I need to work on figuring out what material/size I can use. Currently the box beam is like 2in by 2in and is .25 thick. If that is aluminum I think I am around 65 lbs. Steel...much heavier....

So yea in a nut shell there is the start. I should have had this part done a while ago, but oh well. Many sleepless nights to come!

Ill try to keep you guys posted as I progress....

-bryan

 

[RJ2112]

Bryan,

That seems like a lot of cross bracing on the main deck for such a light load.... As triangulated as the back third is, do you need the cross member in the deck?

 

[bmccrary]

Bryan,

That seems like a lot of cross bracing on the main deck for such a light load.... As triangulated as the back third is, do you need the cross member in the deck?

Rather have too much than too little. I am unsure about how the aluminum will hold up so I just tried to put as many triangles in as possible, lol. Once I get some a bit more nailed down I will put it in Cosmos and see what it tells me. I know the area around that upper shock mount needs the bracing, not 100% on the floor though like you said. The box is 30 lbs and there will be another 60 in the box. So call it 100lbs on the floor...

Also, on the swing arm, Im not 100% on. Just looks weak, but not sure what I can do about it. Once the rear wheel is tied in and the front end is connected to the frame, it should be secure. Afterall there isnt a huge load on it?

Going to draw up tabs tomorrow for the shock mount and the insert for the universal joint and some various other pieces for the swing arm. (spacers and such)

Thanks for the input!

-bryan

 

[RJ2112]

When you need another thing to look at in your copious free time..... see if you can go to simpler forms for the metal in the structure. I would think an L shape would be stiff enough, and at half the metal should be nearly half the weight. Should also be less expensive, and easier to maintain.

At least on the bracing members.....

 

[SeekGod1st]

Just a suggestion, remove some of the cross members (or use lighter weight material for the cross members) and use a grating on any flat spots.

It seems like your losing some cargo space with the back fin protrusion. Why not go completely flat to the beginning of the wheel assembly then straight up, then flat over the wheel giving you more useable space in front of the wheel and on top of the wheel, but make sure you angle brace it.

If you do this you acheive more usable area and may be able to shorten your trailer to save weight if needed.

Again, just a suggestion, I'm no engineer, if it helps use it if not sorry to bug.

 

[RJ2112]

"Also, on the swing arm, Im not 100% on. Just looks weak, but not sure what I can do about it. "

You could add a swingarm brace, just because it would look cool.....

 

[bmccrary]

Just a suggestion, remove some of the cross members (or use lighter weight material for the cross members) and use a grating on any flat spots.

It seems like your losing some cargo space with the back fin protrusion. Why not go completely flat to the beginning of the wheel assembly then straight up, then flat over the wheel giving you more useable space in front of the wheel and on top of the wheel, but make sure you angle brace it.

If you do this you acheive more usable area and may be able to shorten your trailer to save weight if needed.

Again, just a suggestion, I'm no engineer, if it helps use it if not sorry to bug.

In order to make it easier I might do that. The only reason for the angles is to get the upper shock placement where I would like it. As for the cargo room, I wont be making my own box now, I will be purchasing a premade box, so as long as the floor is big enough for that box to rest I am ok. No worries on usable room with this route. Thanks for the suggestion though. Making it vertical will reduce the number of odd angles.

-bryan

 

[SANGER_A2]

"Also, on the swing arm, Im not 100% on. Just looks weak, but not sure what I can do about it. "

You could add a swingarm brace, just because it would look cool.....

Yeah I thought that. The rest of the design looks so solid compared to the swingarm. I was assuming you were planning to use steel or something instead as there is a LOT of pressure on that part of the design.

 

[bmccrary]

Alright so yesterday was the poster presentation and design expo for Senior Design 1. I talked to several people about my design and from the sounds of it I am on track to start building once a couple more calculations are completed to verify a few things. These can easily be completled over break and materials will be ordered once I return from break and my student loan $$ clears.

I have upped the wall thickness to 1/4 inch over the 3/16 inch of the main chaissis and added some support for the tongue of the trailer and reduced the bracing in the center of the chassis. Total chassis weight is approximatly 80 lbs. I did all the stress calculations on the swingarm design as it is and at this point I cannot see any reason for failure.

So far so good. Planning on ordering several of the bike upgrades in the next week or so. Ohlins rear shock with 150 N/mm spring, Ohlins fork springs, racetech emulators, accuman voltmeter and I have sent my stator off for a rewind (More info on that in another thread).

Look for pictures of the updates soon!

-bryan

 

[DefyInertia]

Sounds like you're progressing along nicely. :thumbup:

Keep in mind that Ohlins will sell you individual fork springs so that you can better dial in your spring rate. For example, if they tell you that .925kg/mm is the best measurement for you but they only offer a .90 and a .95, you can by one of each to achieve .925....

Let us know how you like the new suspension upgrades!