bike trailers for a lawn care business

[auraslip]

Thanks guys!

I went ahead today and got the wood placers in. It holds the mower nice. I use bungies and ratcheting tie downs for extra security.

I also added my 48v14ah SLA pack to run in parallel with the ping. They are in a tupperware box. It is dead center as far forward as possible.

The extra 40lbs really makes a difference in acceleration!

The bad news is that the wobble is now worse. Even scary bad if let it go on it's own. Enough to make the rear wheel slide around


It's a good Ideal to balance the load in the middle, but I'm thinking it's time to move the wheels back a few inches. My only worry is the hitch, the dropouts, and the rear wheel axle. How much weight can they take? My bike is already a heavy chromoly with a ping pack.

I'm confident that once I get enough weight on the rear wheel it will stop or significantly damper the sway.

BUT that doesn't solve the main problem; why doesn't the trailer track true? I believe the answer is that the tongue is not pulling the trailer from the center. It pulls the trailer to the left, the wheel try to over correct, and then it bounces back and forward! Maybe I can rig away so the trailer is puller from the center. That will be the idea final solution, but for now moving the wheels will hopefully be enough.

 

[auraslip]

Another length factor is the distance between the rear wheels of the tow vehicle and the hitch point. When this distance is shorter, the trailer can't "wag" the tow vehicle as much, nor do the "bumps" of the tow vehicle affect the trailer as much.

Great resource!

I'm gonna shorten the tongue first before I move the wheels around.

 

[donob08]

Thanks guys!

BUT that doesn't solve the main problem; why doesn't the trailer track true? I believe the answer is that the tongue is not pulling the trailer from the center. It pulls the trailer to the left, the wheel try to over correct, and then it bounces back and forward! Maybe I can rig away so the trailer is puller from the center. That will be the idea final solution, but for now moving the wheels will hopefully be enough.

auraslip

Think of the trailer hitch arm as if the whole space between it and the WHOLE front of the trailer were covered by a piece of plywood bolted down onto the arm and onto the whole front horizontal frame piece on the trailer. With that bolted in place you easily see that the hitch is pulling on the center of the trailer. As long as the tubing from that front left corner to the hitch is rigid, it's just like that. If the hitch were hooked to the front left corner by a rope, you'd have a problem. That's not the problem here.

If your attempts to extend the hitch arm made it less rigid that would be a problem.

Don

 

[donob08]

auraslip

It just occurred to me that the hitch arm MAY not be rigid enough as they designed it. I think Wike said the carrying capacity was 150# max. You are putting somewhere around 200# on it. Wike probably figured "bicycle speed" 7 -10 mph. You want to do 20 mph. So half again as much weight as they tested at twice the speed. The forces on that hitch tongue are a LOT bigger than Wike expected.

You could make the hitch arm sturdier by running a steel cable from the hitch point on the tongue to the right front corner of the trailer. If it's tongue flexing causing your problem, that should help. In general, maybe you need to adjust expectations and cut speed. How far afield do you need to go to mow?

Don

 

[John in CR]

Yeah, any flexing in that tow arm is going to cause exactly that. Also, how true are the trailer wheels? How does it handle with no weight in the trailer at all? A wheel problem would show itself regardless of weight, while flexing in the arm will increase with weight.

 

[auraslip]

Okay the tongue does flex. How do I know this? Because I moved the axle back six inches, and now lifting the tongue is probably about 40-50lbs. Enough to flex the tongue. Enough to move the hitch on the bike down. Enough to pull the orange rubber thing and stretch it out! Not good at all!

The good news is that it kills the wobble. I know it's still lurking back there, but I can cruise at 27 mph (relatively) safely and without any sway or wobble.

I also shortened the tongue by 4 inches. This is supposed to make the trailer more stable.

The wooden cutouts.

I packified my SLAs

Loaded.

 

[auraslip]

How does it handle with no weight in the trailer at all? A wheel problem would show itself regardless of weight, while flexing in the arm will increase with weight.

It handles great!

 

[donob08]

Okay the tongue does flex. How do I know this? Because I moved the axle back six inches, and now lifting the tongue is probably about 40-50lbs. Enough to flex the tongue. Enough to move the hitch on the bike down. Enough to pull the orange rubber thing and stretch it out! Not good at all!

The good news is that it kills the wobble. I know it's still lurking back there, but I can cruise at 27 mph (relatively) safely and without any sway or wobble.

auraslip

.. If the tongue has 40# - 50# at 15% that would mean your load is 266# - 339#. I'm not sure it's that heavy. Total up the weight of everything on there. Take 15% of that. Use a scale and rearrange things to get just 15%.

..You show the tongue bending down. I was talking about the curve in the tongue bending to be closer to straight. That bending and snapping back would make a wobble.

..I would NOT put the gas cans in front 4 gals of gas weigh about 30# if those are 2 x 5 gal cans 10 gals that's 80#. Full to empty will change your weight distribution a lot. Put changeable things over the axle.

..Moving the axle back is just the same as positioning the weight further forward.

 

[donob08]

auraslip

..I just had a thought (somethin new), since relocating the axle on your yikes trailer is so easy, just take out the self tapping screws that locate the axle mounts on the side pieces. Put a scale (bathroom type, whatever) under the tongue (with the trailer level) and slide the axle back and forth until you get 15% of the weight on the tongue.
.. I know you don't have freedom to locate the stuff anywhere you want, but I would put the things that change weight appreciably during a day's mowing near the axle. The gas cans could go on a rack above the mower at the midpoint.

..I think that (and maybe stiffening the tongue against horizontal flexing) will be as good as it gets.

Don

 

[John in CR]

No need to do anything until you reinforce the arm going from the trailer to the bike. The problem isn't the weight distribution, it's that arm flexing, and it's not up and down that's the problem. It's the weight you are pulling, and when the angle of that bend changes with flex, it changes the direction of the rear wheels. That turns the trailer, making it flex the other way, and this progresses into the wobble. There's no way you should ride it pulling all that weight more than 5-10mph until you address this issue. All it would take is one good bump and the trailer could whip one way and then the other, and you're screwed at 20mph or more.

You should really redo the whole connecting method to end up pulling that trailer from the center with that amount of weight, but some significant reinforcement may get you by. No car or truck trailer in the world would ever be designed like that. It is really just for light loads and pedal speeds, and is dangerous in the manner you are using it. The wobble gave you ample warning, so go ahead and correct it.

 

[John in CR]

Also, take a look at your pick...a quick connect skewer holding that kind of weight??? It even looks like the thing is about to come out of the dropout on the trailer hitch side. Please don't turn into a statistic that causes your mother to make it her mission to outlaw e-bikes.

 

[auraslip]

Also, take a look at your pick...a quick connect skewer holding that kind of weight??? It even looks like the thing is about to come out of the dropout on the trailer hitch side. Please don't turn into a statistic that causes your mother to make it her mission to outlaw e-bikes.

I agree completely. I took the pic as I was putting the trailer up. I was surprised, but glad I caught it before I did anything besides a test run.

You should really redo the whole connecting method to end up pulling that trailer from the center with that amount of weight, but some significant reinforcement may get you by.

Are you saying I should mount the arm that connects to the bike from the center of the trailer? Do you think that'd make a difference? or do you mean pull the trailer from a center point on the bike?


I can't really blame wike for this. They didn't have an ebike in mind when they built this kit. All they had was a 150lbs weight limit.
Perhaps I should get a lighter weight push mower and ditch the SLAs.....

Put a scale (bathroom type, whatever) under the tongue (with the trailer level) and slide the axle back and forth until you get 15% of the weight on the tongue.

I will try to find a scale! Do you know if it should be %15 of load weight, or is it %15 of trailer weight + load weight?

I think that (and maybe stiffening the tongue against horizontal flexing) will be as good as it gets.

Any ideas on how to stiffen it?

 

[REdiculous]

Any ideas on how to stiffen it?

Earlier in the thread someone posted a pic...instead of one tube running up to the bike, make it two.

If you're talking about that rubber-deal, I dunno.

wait...SLAs and gas on the front?

 

[John in CR]

"Are you saying I should mount the arm that connects to the bike from the center of the trailer? Do you think that'd make a difference? or do you mean pull the trailer from a center point on the bike?"

Yes, center of trailer, which will require attachment to the centerline of the bike...Probably a tongue for the trailer that arches over the rear wheel to the seatpost.


To stiffen in the meantime, probably the stiffest without getting too heavy with strong metal would bet to use some plywood that attaches to the trailer itself and the trailer tongue all the way up to the big, so the tongue can't flex left and right. Something like this in the hot pink as the added plywood, but make it 1 piece right on top of the arm attached with bolts at at least a couple of points on the trailer and 5 or 6 on the arm.

 

[donob08]

auraslip

..I think you can see you have everyone's attention. We are concerned about your safety. As far as the 15% number, you can just use the weight of your stuff. Your mower spec sheet tells its weight. The trailers weight is only about 30# and it is balanced about the axle, at least when the axle was centered.

..When you shortened the tongue, that put more weight on the hitch. Since the front extra 15# (from that old diagram) are moved closer to the hitch, while the distance to the axle stays the same, more weight is put on the hitch. Then, in addition, you moved the axle back, more weight, so you gave it a double whammy of putting weight on the hitch.

..Using the scale and finding the right place for the axle should let you recover.
..I think forgetting about the SLA's would be a good thing. And think about things that would mess up the good balance through the day, like the amount of gasoline.

..John's idea of plywood sounds good. But the main thing is get the tongue weight right. If that orange connector gives out, nothing else will matter.

BE CAREFUL

Don

 

[John in CR]

Don,

I'm not sure more weight on the axle of the bike's rear wheel is much of an issue. I think the main issue is the flex in the lateral direction of that single arm support. As that thing flexes like an elbow, the trailer wheels no longer point straight ahead. The trailer tracks that direction, making the arm go all the way past neutral and flex the other way, so the trailer tracks back the other direction. Think of that arm as a spring where stretching it points the trailer wheels to the right, and contraction points them left. That elastomer at the hitch might even be part of the problem, but I think the changing angle of that bent bar is the real problem, because with that weight the trailer will begin to whip back and forth.

I hope no one is putting their kids in trailers with that kind of bike attachment. I can see someone quickly getting out of control going down a hill.

John

 

[evblazer]

The trailers I have at home have springs which are going to cause the same issue most likely. I honestly like the bob mount my wife has of course you can't use a single wheel trailer for what you are doing I can't see why they can't make a trailer somehow that mounts to both sides of the axle and then pivots back at the trailer attachment on a ball joint or something.

 

[auraslip]

Hello Shelby,



Here are a few suggestions:

The trailer does not need to be further back than 4” from the rear wheel of the bike, the extended tube that has the tow bar attached should not extend further than 8’ from the frame of the trailer. The tow bar should be snug on the extended tube. If there is a bit of play on the extended tube remove the tow bar and wrap the extended tube with tape and put the tow bar back on. Hope these suggestions help.



Anna Shaftoe

Wike Bicycle Trailers

hrmmm the tow bar that came with the kit has play on the riveted end.....I'm gonna drill the rivets out and bolt it on.

 

[donob08]

Don,

I'm not sure more weight on the axle of the bike's rear wheel is much of an issue. I think the main issue is the flex in the lateral direction of that single arm support. As that thing flexes like an elbow, the trailer wheels no longer point straight ahead. The trailer tracks that direction, making the arm go all the way past neutral and flex the other way, so the trailer tracks back the other direction. Think of that arm as a spring where stretching it points the trailer wheels to the right, and contraction points them left. That elastomer at the hitch might even be part of the problem, but I think the changing angle of that bent bar is the real problem, because with that weight the trailer will begin to whip back and forth.

I hope no one is putting their kids in trailers with that kind of bike attachment. I can see someone quickly getting out of control going down a hill.

John

John

..The reason I think getting the weight correct is that, right now, there is so much weight on the coupler that it might fail.

..That makes everything else secondary. REDUCE THE WEIGHT!.

Don

 

[donob08]

Hey all

..You know I think exchanging ideas on the web is great because you get exposed to so many people's ideas. Unfortunately, the communication efficiency isn't nearly as good if we were all able to stand in auraslip's garage and could exchange ideas directly.

..I think we have demonstrated that "shortening the tongue makes trailers more stable" and "moving the axle back helps" don't work. Those vague pharses don't say "how far" or "until...." There needs to be a plan, a specification, how ever you would like to describe it.

..Arranging things so that 10% - 15% of the total weight of the trailer weight is on the hitch is a measurable goal for a plan. If rearranging stuff on the trailer accomplishes that goal, we can test to see if our plan was a good one. If we can't rearrange stuff and instead decided to move the axle back in order to get 10% -15% of the weight on the hitch we can do it and test how effective the plan was. Same for shortening the tongue which increases the weight on the hitch. If we know we have accomplished 10% -!5% and things don't work then we need a new goal.

..So far we have changed things by some amount with no goal, the results were bad as far as performance (because the coupler is in trouble, even though we did eliminate the bad tracking), but we don't have anything we can measure to quantify what our changes did. I suspect we have WAY MORE than 15% of the weight on the tongue, but we don't know.

..I'd say if the connector looks ready to break, the change was bad. But that doesn't quantify anything measurable about the change. Now, if we measure the weight on the hitch, knowing the weight of the stuff on the trailer and the number is between 10% and 15% and the coupler is looking sad, then we know FOR SURE, there is TOO MUCH weight on the trailer. 15% of trailer weight on the hitch is a maximum spec. If the tongue can't take it. Remove the SLA's or whatever it takes to get 15% of the trailer weight friendly to the tongue.

..After we get that right, and have facts about the condition we have generated then we can worry about changing the design of the tongue, plywood gussets, central tongue to seat post .... First we need FACTS describing the situation that we have.

Don

 

[auraslip]

donob08 - First step was to reduce the weight on the hitch. I did this by putting the mower to the front of the trailer. Moving the axle forward a bit. I also moved the tupperware container and SLAs to the back.The way the slas fit in the box is movable, so if I have balance issues i can correct it . I've arranged the gas cans so they are directly over the axle. The orange hitch piece seems well now. I don't have a scale but I imagine it's probably 20lbs on the hitch.

Step two was to take Wikes advice and shorten the tow bar so only 4 inches is between the trailer and rear tire. I also drilled out the rivets in the tow bar that had play in them, put two bolts through it, put an extra bolt on the other side of the tow bar connector, and wrapped both ends of tubing that go in the connector with tape. There is still a tiny bit of play in the tow bar BUT

Now with only the mower and SLAs there is no sway at ~23mph. I don't know how fast I was going because it is dark outside and my computer isn't back lit. I will find out tomorrow how this works with the weed eater and mostly full gas cans.

I believe the bulk of the problem was weight distribution AND a big problem with the design of the kit in the tow arm which flexes tooooooo much. If the sway is not fixed, I am going to reinforce the tow arm with wood or metal.

 

[John in CR]

Great, it sounds like you're well on your way to nailing it down. I think some of us were picturing a really young guy taking off with a heavy trailer and get yourself badly hurt. I'm glad you're not just blowing and going. Once you get it all straightened out, just watch your braking distances.

Have fun with it.

John

 

[donob08]

auraslip

..Sounds ALL GOOD. I'm glad you worked things out. You certainly have applied a lot of energy to getting this fixed. I hope soon you'll have enough lawns so that they will take up all of that energy.

..Good luck with the business.

Don

 

[EVan]

Sounds like fun!

In the EV world, there was a guy called Steve Clunn in Florida who had a full lawn service company running from his converted electric pickup truck, towed a ride-on electric mower behind it and plugged in at a few customers yards to do the full round.

You could do the same on a smaller scale, with a really good Li-Ion push mower, market yourself as eco / green lawncare.
Let the bike charge while you are mowing, then let the bike and the mower charge while you use a corded weed-eater or edger or whatever.

Gas mowers are really badly polluting, more so than any modern truck or car.. as a cyclist that affects you more than most..

 

[EVan]

By the way you might want to electrify the trailer rather than the bike, let that carry some cheap SLA batteries as well as the other weight, put two cheap hubs on it with small wheels for plenty of torque. Cheaper and more stable IMHO,.