when a grabrail becomes a rack

[outlaw]

As i was not useing the panniers over winter i took the frame off looks nice naked, but still wanted a rack/topbox to use so i made one i used a spare grabrail that i bought see below.

[McF]

Good job!

But, I would be very careful about how much weight you put on there.

All the weight on the rack plate will rotate around the grab handle because there are no members in compression to restrain the twisting on the handle.

In your garage, the static load probably looks fine to start with, but think about when you're on the road - every bump and pothole will create a lot of dynamic load and that baby will start bouncing around.

I'd suggest no box and only lightweight stuff, like waterproofs sandwiches etc.

[outlaw]

Thanks for that, i may run some tubes down to the frame like the givi rack to support it ,
outlaw

[outlaw]

Hi, mcf,
i have posted a second photo for you to look at would you think the green line,s braced would be enough or follow the yellow lines down to the frame as a givi rack,(looking at the rentec rack it is bolted where the grabrail goes and for the strenth has a down tube( green line) welded to the loop on the front of the bar, any advice is welcome
regards john

[McF]

Hi Outlaw
I'm no expert, but have lots of experience of failure and as we say in T'republic o' Yorkshire "the man who never made a mistake, never made owt!"

If you can make some supports that follow the green lines it will be better than present. The Renntec rack is only rated for 2-5Kg and I think that is likely to be related to the lack of vertical components.

If you can make some supports that follow the yellow line it will be a lot more resilient for you.

I'd also suggest, if you go on to make MkII, that you replace the flat bar used under the plate with something that has a deeper section (like angle, channel, or box), the deeper the section (Second moment of area), the stronger it is.
Take a plastic ruler, lay it flat side down with half across the edge of a desk, then press on the unsupported end, it will flex
Now rotate the ruler through 90 degrees, so that the flat side is vertical, but still with 50% unsupported. Now press down on the free end and the ruler will not flex.
That is depth of section

You could always put the wing rack less panniers back on?

[outlaw]

I have built my own rack for my bike and tested it i put a topbox on and filled it with a car battreys and with tools not sure of the weight, but the rack held, it was a bit unstable going round the bend with that much weight in the box it was like having some one very large on the back, photos to follow,
outlaw

[rj2para (Bisto)]

Bricks may have been safer than batteries .

Looking forward to more pictures.

R.

[outlaw]

here are the photo,ssupprised me how strong it was what you can not see is the bracing under the panal out of sight,

[McF]

Now that looks like a proper job - good engineering
and looks good too
Well done

[rj2para (Bisto)]

I agree with McF very.. tidy lines.

Nice project Outlaw.

R.