Reached the limit of my brompton..

[cwah]

With that round shape you don't need a plate, but you also don't need that clamp @ that price !!


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Or can I use this one?
60mm 2.4" 2 3/8 Inch U-Bolt Clamp Universal Heavy Duty Custom Car Kit Exhaust | eBay

I would buy 3 of them, and drill holes inside this 3 mm steel plate:
stainless steel sheet 100 x 100 x 3mm 304 | eBay

Should be enough to manage 14kg?

Ideally it should be able to carry 20kg as sometime I use my brompton for carry my groceries lol

 

[Old_Dave]

There are several ways of skinning a cat, lol .. and as long as you achieve the result then just pick whichever method of attaching the block or creating a new one that you fancy


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[neptune]

@cwah. I would say that the clamp you linked to would be OK provided you match its size to the frame size. I would say 2 clamps, space 2 inches apart vertically would be OK. I would think that would easily carry 20kg.

 

[cwah]

Thanks guys. Just purchased 3 of them (even if I only use 2) on Ebay. They are quite cheap so it's ok.

Hopefully it's going to work!!

 

[jerrysimon]

Yes this looks good, should work and will carry additional weight. I was trying to suggest keeping the existing mounting and one bolt.

You may have to cut the Brompton luggage block to make it sit flush against the new mounting plate.

Regards

Jerry

 

[cwah]

My second brompton has its bolt that snapped inside

Must be the cold outside. At 0C the metal is probably less flexible and easier to break...

DAMN!! I can't travel anymore now!!

 

[neptune]

@cwah. Jolly bad luck old chap. This time, get a professional to drill it out for you. If you get it done, I would recommend you fit new bolts once a year, as I think metal fatigue is the problem.

 

[cwah]

Not sure if it's metal fatigue as the failire happened on both bike at almost the same time...
Lesson learnt is that these bolts are not strong enough to handle 14kg bag. The custom attachment seems to be the way to go.

Still waiting for the U bolts to arrive!

 

[Scimitar]

It's not a dead weight of 14kg - it's levering the hell out of them as it bounces up and down. Even if Brompton actually say the limit is 10kg, I'd be very cautious about that figure, too. You will find the exhaust clamps will never snap even with your 14kg on them - just don't overtighten them and bend the steering tube.

 

[cwah]

Guys, I finally received the exhaust clamp today.

I started a prototype on a cardboard:

- I've put the 2 exhaust clamp on the top of the frame because on the bottom it may slide with the weight and wouldn't clamp that well.
- I added 4 layer of small cardboard to prevent the steering tube to touch the battery box. I'm planning to replace them with wood as it's quite lightweight.
- The last and longer layer represent the battery box. I'm planning to directly fit a box of 8mm polycarbonate sheet on it.


A view of how the back side of the battery box would be clamped:

I'm still wondering if 8mm polycarbonate sheet bolted in 4 area would be strong enough to handle 20kg bag with vibration and jump...

I'm thinking about adding a steel plate on top of that... or maybe use a 3rd exhaust clamp to have 6 fixation point?

What's nice about that is that I won't need to be worried on my battery being stolen after that as it would be strongly clamped to the bike.



What do you think guys? 8 mm polycarbonate with 4 fixations point should be enough? All goods, can I go into production?

 

[Hugh]

I'm no expert on this kind of thing, but I would certainly not trust a fixing that was only through polycarbonate - it'll rip out with the weight in no time. I'd say your drilled steel plate, or at the very least, some very wide washers, would be essential.

Good luck!

 

[NRG]

To get strength you will need to space the mounting points out as far as possible, you don't have much room as the stem is short but try to get them as far apart as possible...also don't over tighten those clamps they can exert considerable force!

 

[Deleted member 4366]

I'm with NRG: You'd be better putting one clamp above the main frame tube, and one below. Don't over-tighten them or you could distort your steering-head bearings.

 

[cwah]

Thanks guys, I updated it:

On the bottom I'll use 2 angle bracket to support the weight. And potentially an additional steel sheet to support the polycarbonate box... Not sure if I use the steel sheet or if I can just add a third clamp

Looks like this now:

Not very confident on the clamp below. Looks like it's floating, all the weight will be distributed on the top clamp.... hmm...

Do you think it's ok for a 20Kg target?

 

[cwah]

Finally decided to keep the brompton holder. As it allow quick release and it's much more lightweight than what I have.

Here's the set up:

The little metal holder support the torque from the clamp:

It actually replace the broken bolt... in a better way.

Seems much stronger than what I had initially. Thinking about keeping it like this for now, doesn't seen to need the additional clamp.

I'm proud of me lol.


ps: I'm still thinking of updating with a customized holder... but for now this solution appears to be the simplest and lightest.

 

[Old_Dave]

Well done you

There are many ways to skin a cat, each one has its own pros and cons..

The pro being that you sorted it.. and you sorted it your self

 

[Deleted member 4366]

There's always a simple solution. You just found it.

 

[cwah]

Hehe, this idea just came to my mind like... today!! lol

I'm sure you some of you told me to do it that way but it didn't come to my mind.

What I'm still not sure is if the top part of the plastic that support the clamp may erode over time with vibration and torque. I probably need to add an additional metal sheet to support this part.

Other than that, that's too bad I didn't add that clamp initially when it only had 2 m5 bolt supporting 14kg. Would have saved me a lot of hassle!

 

[Old_Dave]

What I'm still not sure is if the top part of the plastic that support the clamp may erode over time with vibration and torque. I probably need to add an additional metal sheet to support this part.

Correct

But the wear should stop when the U bolt touches against the steel plate wot acts as the original washer for the old bolts (which is why the stainless jubilee clips could of been yet an another option..lol)

 

[cwah]

yeah, for the vibration on the left to right it should be fine with the original steel plate. But I'm wondering about the vibration from top to bottom. Probably need something.. But too lazy for now to do anything.

Will play with my bike as is lol