Cargo box?

EVBob · Aug 21, 2017

Greetings All,

I see there is an aftermarket hitch that one can add to the i3 - assuming for the intention of transporting bicycles: https://torkliftcentral.com/2014-2017-bmw-i3-ecohitch-reg

It looks like the limit is 200 lbs. Do you think the i3's frame could take this weight in the rear for a longer trip with out long term damage to the non flexible CFRP frame? It would be nice if one could put a light weight rack (or cargo container) on the hitch and carry additional light bulky items. something like this would be nice, but have the feeling the setup probably weighs over 100 lbs by itself: https://www.stowaway2.com/standard-cargo-carrier-black

Maybe something like this (preferably something that could swing or fold away so you could open the rear hatch) with a waterproof bag strapped to it would be more efficient: https://www.sportsmansguide.com/product/index/guide-gear-aluminum-atv-cargo-carrier?a=1935503&pm2d=CSE-SPG-15-PLA&utm_medium=PLA&utm_source=Google&utm_campaign=CI&gclid=EAIaIQobChMIyejNmM_o1QIV2YSzCh2SAgVREAQYASABEgJRhPD_BwE

jadnashuanh · Aug 21, 2017

The actual stress applied to the frame is partly dependent on how deep the thing is...i.e., how far out it projects. The further, the bigger the lever, the bigger the force. Since BMW does not offer a hitch for this vehicle, anything you add on is a guess. On my ICE, I have a hitch and I use a basket purchased from Harbor Freight made of aluminum. The basket itself doesn't weigh much, but it is deeper than the one you liked to. I use mine to carry a folding recumbent tricycle. That basket is rated for a load of u to 500#, which is more than my hitch is designed for, and certainly more than the i3's hitch can handle as well.

If the hitch is designed well, spreading the point loads out, it should not damage the CFRP, but you have to take the company's word for it...that may or may not be well qualified.

ChristopherEmmanuel · Aug 22, 2017

Hi, I thought the chassis was aluminium and the CRFP life cell was sitting on the chassis? If this were the case then it would be solely dependent on the rear suspension springs exceeding the limit. Just a thought :idea:

alohart · Aug 22, 2017

ChristopherEmmanuel said:
Hi, I thought the chassis was aluminium and the CRFP life cell was sitting on the chassis? If this were the case then it would be solely dependent on the rear suspension springs exceeding the limit.

You would be correct. Attaching a trailer hitch to CFRP would be verboten.

EVBob · Aug 22, 2017

ChristopherEmmanuel said:
Hi, I thought the chassis was aluminium and the CRFP life cell was sitting on the chassis? If this were the case then it would be solely dependent on the rear suspension springs exceeding the limit. Just a thought :idea:

alohart said:
You would be correct. Attaching a trailer hitch to CFRP would be verboten.

Thanks for chiming in!

Looking at the installation video again - it looks like the hitch installs to the aluminum frame -- https://youtu.be/tc4jgJuXbIM

So should be alright - aluminum being a bit more forgiving than CFRP when it comes to odd stresses/loads?

alohart · Aug 23, 2017

EVBob said:
Looking at the installation video again - it looks like the hitch installs to the aluminum frame

The mounting points were on the rear bumper impact bar which is likely steel. It's painted black whereas the aluminum frame parts that I have seen are unpainted.

When I wanted to lift both rear wheels with a floor jack, I was unable to find a location in the rear that looked like a strong frame member. So it might not be possible to mount a trailer hitch rated at a higher load than the 200 lb. of this trailer hitch.

EVBob · Aug 23, 2017

alohart said:
EVBob said:

Looking at the installation video again - it looks like the hitch installs to the aluminum frame

Click to expand...

The mounting points were on the rear bumper impact bar which is likely steel. It's painted black whereas the aluminum frame parts that I have seen are unpainted.

When I wanted to lift both rear wheels with a floor jack, I was unable to find a location in the rear that looked like a strong frame member. So it might not be possible to mount a trailer hitch rated at a higher load than the 200 lb. of this trailer hitch.

200 lbs would be just enough (though more would be better ;-)) - I just wanted to make sure it really could take 200 lbs on the hitch with the dynamic pressures of hitting bumps and potholes.

Thanks,

Bob

brastic · Aug 24, 2017

I have the hitch and yes is does bolt to the metal bumper mounts like in the video. I cannot say how much force it can take. That would be for TorkLift to supply. I can say that they built a good product, it is thick metal and someone heavy duty. I am also happy how easy it was to install. What you see in the video is what you do.

EVBob · Aug 24, 2017

Thanks for chiming in!

Did you install it yourself or have it done at a shop?

If you did it yourself, how long did it take you? What would you say was the harder parts of the install? It look like removing the bumper and unplugging the parking sensors may be the hard part, requiring two people?

If you had a shop do it, can I ask what the charge was?

brastic said:
I have the hitch and yes is does bolt to the metal bumper mounts like in the video. I cannot say how much force it can take. That would be for TorkLift to supply. I can say that they built a good product, it is thick metal and someone heavy duty. I am also happy how easy it was to install. What you see in the video is what you do.

jadnashuanh · Aug 24, 2017

The hitch may attach to metal, but that metal piece attaches to the CFRP frame at some point, as does everything else that is load carrying.

alohart · Aug 25, 2017

jadnashuanh said:
The hitch may attach to metal, but that metal piece attaches to the CFRP frame at some point, as does everything else that is load carrying.

I don't think that's the correct description of the i3 chassis. The aluminum frame is the load-bearing component of the structure with the CFRP passenger cell bonded to the aluminum frame and providing collision protection to passengers. The aluminum frame, suspension, bumpers, and thus trailer hitch could be a single connected unit without the CFRP passenger cell being attached as shown in the photo below.

brastic · Aug 25, 2017

EVBob said:
Thanks for chiming in!

Did you install it yourself or have it done at a shop?

If you did it yourself, how long did it take you? What would you say was the harder parts of the install? It look like removing the bumper and unplugging the parking sensors may be the hard part, requiring two people?

If you had a shop do it, can I ask what the charge was?

brastic said:

I have the hitch and yes is does bolt to the metal bumper mounts like in the video. I cannot say how much force it can take. That would be for TorkLift to supply. I can say that they built a good product, it is thick metal and someone heavy duty. I am also happy how easy it was to install. What you see in the video is what you do.

Click to expand...

I did the install myself. It took a bit under two hours as I was working by myself most of the time. I would need a second hand when removing the and attaching the bumper panel. As you can see in the video, it is not a hard job. Just take your time. I can say that watching the video twice was better than the written instructions. The big thing here is using a torque wrench. Some of the bolts go into aluminium. When it states 17 ft-lbs, they mean it.

brastic · Aug 31, 2017

jadnashuanh said:
The hitch may attach to metal, but that metal piece attaches to the CFRP frame at some point, as does everything else that is load carrying.

The hitch is attached to the metal part. You could fully remove the CFRP part of the car and the hitch would still function.

Cargo box?

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