Which Rack Design do you prefer?

[steve mercier]

You are far more likely to get you eggs home from the grocery store if your rack is suspended. Your kid riding on a bike seat will be safer and more comfortable as wellView attachment 51632

Oh certainly more comfortable for that child you have apparently kidnapped. I cannot find any weight capacity ratings for either type of the R+M racks. Which one would you say is rated for heavier loads?

 

[Ravi Kempaiah]

I cannot find any weight capacity ratings for either rack.

Old Man mountain racks are approved for 70lbs. But if you are on a bumpy terrain, even 50lbs load on rear rack like OMM will change the ride characteristics.
On normal roads, this may no matter much unless you are going over bumps. If you have suspended rack, the rear suspension will be much more sensitive as it will not be bogged down additional 50lbs moving up and down.

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The Old Man Mountain Classic Rack is our signature bike rack. Durable, strong, versatile cargo racks, Backed by a Lifetime Warranty.

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[Ravi Kempaiah]

Nice job, Ravi!

This appears to be a cantilever design, right? A stronger design would be one supported by the axle itself, a la Old Man Mountain. I have an Old Man Mountain rack on my full suspension Haibike e-mountain bike, and it is VERY sturdy. I carry delicate photo equipment in my well-padded panniers, including long telephoto lenses. Did you consider an axle-supported rack? (As a retired architect I am interested in structural design decisions.)

Thanks. I did consider OMM style rack. That is pretty easy to do.
It works well for <25lbs load and on gravel trails but you will notice the difference jumping off 8" curbs or going over big bumps.
With a fully suspended rack, suspension works much better. I put over 2000 miles on my Riese and Muller Delite and it was a truly versatile bike. So, with that experience, I decided to go with the cantilever design.
You get the full benefit of rear suspension.

 

[Johnny]

Hey Folks,

I am needing a few extra pairs of keen eyes to get some feedback on the design.
We just designed the suspended rear racks and they are made strong with heavy duty tubing to withstand 55lbs of cargo. I am hoping to make it compatible with Racktime accessories.
But aesthetically, which design do you prefer. Any suggestions or feedback?

Option 1: Trapezoid design

View attachment 51572

Option 2: Angular Design

Note* suspension travel is fully compressed and that is why the wheels are closer to the rack but it's fine.

View attachment 51573

Ravi, I also voted for option 2 but it is mostly for visual appeal.

I suspect that you may need extra reinforcement between the two connecting rods to the seat tube, they are too close and somewhat parallel moreover the horizontal distance of your load is quite a bit far from the points of connection. That may put a lot of perpendicular force on them which may cause trouble.

 

[Ravi Kempaiah]

Ravi, I also voted for option 2 but it is mostly for visual appeal.

I suspect that you may need extra reinforcement between the two connecting rods to the seat tube, they are too close and somewhat parallel moreover the horizontal distance of your load is quite a bit far from the points of connection. That may put a lot of perpendicular force on them which may cause trouble.

Thanks John.
The rack will be tested (stress and fatigue) for over 400 hours at 100lbs loading (operating limit of the rear rack will be 55 lbs or 25kgs) in dynamic conditions.
Once all tests are done, only then frames will go into production.

 

[mikegs430]

I voted for option 2 I like your cantilever design and the shape compliments the Haibike very well. I believe for all the reasons you state that a cantilever design will work best on a full suspension Bike. clearly there is more stress but that can be overcome with good materials and design. I wish this was available before I bought my OMM.

 

[webcurl]

Your original Option 2 looked like if it were at the high end of the load limit it would be able to flex a bit over almost all of the rack frame material adding a small amount of extra suspension, adding struts for lower panniers limits this.
Pivoting joints at certain places could improve this?

 

[Ravi Kempaiah]

Pivoting joints at certain places could improve this?

Thanks for this very interesting suggestion. I will try to implement this once we have the frames ready. The most important thing is to design and test the frame that could withstand 100 lbs load at the seat tube joints.
This will need extensive FEA modeling and actual frame testing using physical loads.

 

[webcurl]

When i was thinking about this stuff i was going to replace my R&M Supercharger1 (hard tail) rear rack with a custom Chrome Molly rack with top swivel connection and these on the bottom struts of the rack:

or even a lighter version of: