Trailer power

[billvon]

Sorry if this has been asked before -

I have been considering converting an Ibex trailer to a powered trailer by adding an X5305 Crystalyte hub motor. (Alternatively a 400-series motor if I can't talk my mech-E friend into designing an adapter plate for the small rim.) That way the bike itself is an off the shelf bike with whatever gearing/brake/wheels you like, and the motor/battery is contained within the trailer.

I am thinking that this may lead to odd handling, since the trailer can potentially get out of line and start pushing you laterally, but I don't think the dynamics are much different than trying to stop on a downhill with a trailer (which after all wants to keep going.)

On the plus side, the trailer is removable, the suspension on the Ibex leads to less vibe/shock on the batteries, the larger area is a great place to mount a solar panel/sunshade and it would be great for touring (which is probably the only way to get enough weight in the trailer to give you decent traction!)

Anyone have any experience with such things?

 

[Rassy]

Hi billvon. See my latest project at:

http://endless-sphere.com/forums/viewtopic.php?t=2360&sid=c99cdb68aa475f5e2c422c04d694d3ae

About a year ago, after trying first a 24V scooter motor and then a 36V hub motor on a MB, I needed more power to climb the 15% to 20% hill between town and my house. So I built a two wheel trailer with two hub motors on it. I was also worried that the trailer might tend to push the bike around on corners, but I was happy to experience no noticable ill effects. Eventually I put a third hub motor on the front wheel and about 75# of SLA in the trailer. Then I swapped out the MB for the trike:

http://endless-sphere.com/forums/viewtopic.php?t=703&highlight=recumbent+trike&sid=5df566e9d26c0cef60b15e0c998be4f9

On my current project I used an older Bob trailer with the hard side tote. I replaced the 16" fork for an old 26" MB fork and installed a 20" wheel/hub motor. There was no room in the 16" forks for any kind of motor. Do the newer Bob's (Ibex) have a different fork set up? My Bob trailer has no suspension. I have only made a few short test runs so far, but am happy with the results. Will probable boost it to 48V soon.

 

[vanilla ice]

No trailer experience, but hopefully that will change in a couple months.

I was thinking the lazy way to do a powered trailer would be to buy one of those razor dirt bikes made for kids. Trash the body work and forks. Fit some diy hitch up system. Extend the throttle cable, and you're set. Bats, motor, drivetrain, and suspension is all figured out already. I may try this instead of fitting a motor on a kids schwinn pedal trailer like I'd planned. Kind of the same "no work" mentality as in the dc to dc converter thread. Why build it if you don't have to? These bikes go for pennies on the dollar in the classifieds. Weight is a downside but the frames are beefy and you could swap out for lighter bats, or upgrade things one by one if you wanted.

 

[gwsaltspring]

Hi B;

Is this the kind of thing you had in mind?

http://www.e-ride.ca/Electric_Bikes/Electric_conversion_trailer.htm

 

[Rassy]

Hi gwsaltspring. wow! I found that site interesting. Glad to know there is still a professional conversion of a BOB trailer available. I had read somewhere that the "BOB" folks used to sell a hub motor version, but had discontinued it.

I have a small reservation about the BOB hitch pins handling the motors uplift at the hitch point, but the models shown seem to use the original BOB hitch system.

In the meantime, I am happy with my DIY version of a BOB conversion.

 

[gwsaltspring]

Hi Rassy

I don't wish to hijack B's thread, but I am interested in your trailer build project and asked a Q about the motor in your thread in the Photos & Vids section.

Perhaps we could carry on this dialogue over there :wink:

 

[billvon]

Is this the kind of thing you had in mind?

Funny, there's one that looks just like that that's taking shape in my garage right now!

 

[gwsaltspring]

Hi Bill;

Which motor did you end up deciding to use?

 

[billvon]

Hi Bill;

Which motor did you end up deciding to use?

I am vacillating between a 408 that I have on a 16" rim or an older X5303 without a rim. The 5303 fits in the dropouts (with a little bending) but it will need an adapter plate to work with the 16" rim since there's no room for spokes. (A 20" rim fits without tire, but there's not enough clearance for any reasonable tire.)

 

[fechter]

You might be able to adapt the 5303 by using multiple pieces of U-channel or angle rather than one solid adapter plate. They'd look like really short, fat spokes. They could be bolted onto the rim and the motor.

 

[billvon]

Update!

I put it all together and it seems to work OK. I used a 408 motor, a 40 amp 72 volt controller and two test batteries - a 36 volt nimh and a 72 volt lead acid. Motor is a 408.

Picture is below. Lead acid battery is yellow, nimh is silver, controller is black and not visible is the shunt for a Cycle Analyst. Some results:

36 volt batt 13.5mph 39 volts 250 watts (peak about 450)
72 volt batt 23.5mph 70 volts 700 watts (peak about 1500)

The 72 volt system seems "geared" correctly; my goal is 20-25 mph. Questions:

Do I stick with the 72 volt system or go to a 36 volt system with a motor like a 404? Overall I prefer 36 volt systems due to ease of charging and aux power generation. And with the 40A controller I don't think I will have a problem with available power.

I'm using the "new" 72V 40A controller from ebikes.ca, and it seems to work OK. However, when coasting at 10-15mph, the wheel almost locks up (i.e. jumps and jitters and slows me down greatly) when I am at very low throttle settings. Zero throttle it coasts fine, and higher throttle levels it works as expected. Anyone else experience this?

 

[fechter]

I'm using the "new" 72V 40A controller from ebikes.ca, and it seems to work OK. However, when coasting at 10-15mph, the wheel almost locks up (i.e. jumps and jitters and slows me down greatly) when I am at very low throttle settings. Zero throttle it coasts fine, and higher throttle levels it works as expected. Anyone else experience this?

That's strange ???

I wonder if it's going into regen? If you get the CA hooked up, it will be interesting to see if there is negative current when it does that.

 

[billvon]

it will be interesting to see if there is negative current when it does that.

There is a transient regen current but it goes away quickly. I'll have to find a hill and see if it's sustained if speed is kept up.

 

[Ypedal]

Quote "Do I stick with the 72 volt system or go to a 36 volt system with a motor like a 404? "

I personally prefer the high voltage high-wind count vs lower voltage high-rpm motors.. but that's a preference thing i guess. More gusto from a dead stop is always a bonus !

 

[Rassy]

billvon, looks good. glad to see you got it going. Does sound like its going into a regen mode, and with the suspension on the trailer and relatively light weight (compared to a bike with rider) I would expect some bounce during heavy acceleration or regen braking. Is the suspension on the IBEX adjustable?

Looks like your nimh battery pack and controller could be slung under the trailer like the Canadian one gwsaltspring referred to.

Have you posted a full picture of the bike and trailer someplace?

BTW if you don't already have a good kickstand on the recumbent, this one made for the BOB trailers is very light and works great:

http://biketrailershop.com/catalog/product_info.php?products_id=113&osCsid=56e5765c79f216fd9e179b07e3d6ded1

 

[billvon]

Another update -

I swapped the 408 for a 404 motor and am now getting 23.5 mph max from a 36 volt pack, which is just about right for this application (trailer for medium to heavy loads.) Pulling about 500 watts cruising on the flats at 22mph; current has gone as high as 30 amps during acceleration.

I also went to a different ebikes.ca controller (an IRFB4110 40A 72V one) and the stuttering problem went away.

Overall I am happier with 36 volts since it makes charger and DC/DC converter design a bit easier.

Also, a note - due to the way these controllers are designed (PWM is commanded directly by throttle) the throttle tends to set speed instead of torque. This is often annoying, but for the trailer application quite useful; when the tire breaks loose due to not having enough weight on the wheel it quickly grabs again since the wheel's speed is limited by the throttle.

 

[billvon]

I've been taking the trailer/recumbent to and from work the past few days and have noticed that:

-speed and power is good. I'm maintaining 18-20mph up moderate hills (600-800 watts) 12-15mph up steep hills (pulling about 1200 watts) and about 25mph on flats (300 watts or so.)

-There's an annoying chittering problem when I use a lot of power on bumpy roads. The tire comes unglued for a second, screeches, then grabs again when it settles back down. I know I'm losing a significant amount of power on some of the bumpier stretches, but I can't really think of a good solution (beyond more weight of course!)

-The Crystalyte connectors are not quite up to the junction between trailer and bike. I should really replace them with a more rugged connector.

 

[Toorbough ULL-Zeveigh]

So what speed/watts do you get with the 404 on 72V?

 

[Rassy]

Billvon wrote:

-There's an annoying chittering problem when I use a lot of power on bumpy roads. The tire comes unglued for a second, screeches, then grabs again when it settles back down. I know I'm losing a significant amount of power on some of the bumpier stretches, but I can't really think of a good solution (beyond more weight of course!)

I've experienced a little of this effect, particularly when accelerating while turning and going uphill. Basically, I like my BOB trailer setup and don't plan to change it. However, if starting from scratch, I would move the wheel forward with the cargo areas split on both sides of the wheel. Then the entire load would be balanced on the wheel, effectively increasing the weight on the drive wheel for the same size load.

EDIT: A second thought is the air pressure in the trailer tire. I am only using about 35 PSI, since the weight is so low compared to the rear tire of a LWB recumbent.

 

[Ypedal]

So what speed/watts do you get with the 404 on 72V?

You seriously don't want to run 72v into a 404... the top speed would be un-usable..

 

[Rassy]

Billvon, when you opened this post last year you mentioned putting some solar panels on the trailer. Have you done any experimenting with solar panels yet? I am currently considering adding some solar panels to increase my long distance travel between recharges.