Bike Rack Mechanical Design Paranoia

[EEVblog]

Is Dave's paranoia about the mechanical design of this Yakima car bike rack justified?

[Muttley Snickers]

In my opinion the whole thing looks a bit wonky. A good mate of mine is both a very keen club cyclist and a metal worker/ welder so I will ask him and see what he reckons. With all the turbulence just at the rear of the vehicle I would have thought that metal fatigue would be of concern, particularly if long distances were involved.

A safety chain is mandatory when towing a trailer and I think they shoud make it compulsory that a separate safety chain or strap be attached between the tow hitch and the bike rack, that way if it broke or worked loose whilst travelling at speed the bikes would be dragged rather than bouncing through the windscreen of the vehicle behind.

[wilfred]

Are you certain it is tightened up properly. That  lockable knob should tighten the friction fit wedge so that it doesn't wobble that much unladen. What you were showing looked loose.

Also getting a family of 4 bikes onto that rack means an average of about 13kg per bike. Pretty sweet lightweight bikes.  I also noticed a warning about max speed over speed bumps etc. From which I infer the strength of the top rack is a concern. Not that anyone would routinely go fast over bumps.


Edit. OK I asked a cyclist friend and he thinks the rack shouldn't wobble. He also laughed when I said I thought a 13kg bike was light.

[2N3055]

https://yakimasupport.zendesk.com/hc/en-us/articles/229150287-My-hitch-rack-wiggles-or-has-some-play-after-installation-What-can-I-do-to-eliminate-this-

But I agree, it looks wobbly..It might be designed to withstand all the loads (and it probably is) but it doesn't instill confidence..

[EEVblog]

In my opinion the whole thing looks a bit wonky. A good mate of mine is both a very keen club cyclist and a metal worker/ welder so I will ask him and see what he reckons. With all the turbulence just at the rear of the vehicle I would have thought that metal fatigue would be of concern, particularly if long distances were involved.

That's the thing, we want to use it for 1000km+ trips.

[Muttley Snickers]

I had a chat with my mate and he said a slight wobble is common particularly with folding type frames, he also said some of the spacers which are used to step down from the standard two inch receptacle to the smaller one and a quarter inch can cause problems as well.

Anyway, it could be worse I suppose.   

[EEVblog]

I had a chat with my mate and he said a slight wobble is common particularly with folding type frames, he also said some of the spacers which are used to step down from the standard two inch receptacle to the smaller one and a quarter inch can cause problems as well.

Thanks.
According to linked above the shim is the recommended solution 

[ChunkyPastaSauce]

While tightening the large knob, make sure to jiggle the rack at the same time and press into the receiver lightly (with pin in). Otherwise it will seem tight at knob but wont actually be tight in receiver.

Also the 45 degree screw on the receiver, should be tightened last. The rack needs to be retained with the main knob. If you tighten the 45 degree screw first, the rack hitch wont sit flush in the receiver when you tighten the rack knob (you also wont be able to fully jiggle when tightening knob). Most receivers don't have the screw and it is meant for anti rattle with traditional loose fitting hitch I think, not meant to retain the hitch or as a safety.

[Spark-Doctor]

You have several problems going on with this design. From what i can see in the attached pictures, the big plastic screw draws back on the ali wedge which in turn acts on the rubber block, clamping the unit. The trouble is, that rubber block has 2 slots in it and i susspect that is where the weeble wooble is comming from. As you are traveling down the road, the whole frame is going to move due to wind, road conditions, bad driving  ect and the whole frame will start to resonate at a frequency. This is going to cause stress in the welded joints and if it gets to a certain point, fractures may occure.

To analize the design better, i would need to know the dimentions of the rack as well as the bikes, materials and weights.

Ian

[nctnico]

I suppose it has been certified? In the Netherlands this type of bycicle rack from 'twinny load' is pretty much the standard:


It clamps onto the tow bar and is pretty much rock solid.