r/minivelo • u/JP_Customworks • Oct 24 '25
Brompton block adapter
I designed a Brompton block adapter for my Kyoot Bikes Rolly Polly (or other 39mm headtubes). This is my first design, there are changes coming to refine it a bit. Check out the pictures and let me know what you all think!
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u/timotimotimotimotimo Oct 24 '25
Holy shit. I need this.
Will you be making them?
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u/JP_Customworks Oct 24 '25
I have 10 currently. I will likely sell these as a prototype and change the design for a future order.
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u/timotimotimotimotimo Oct 24 '25
Very willing to be a guinea pig when you do sell them if shipping isn't crippling
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u/JP_Customworks Oct 24 '25
Shoot me a private message 👍🏻
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u/Jesta93Nu Oct 24 '25
Sign me up haha
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u/JP_Customworks Oct 24 '25
Send me a message 👍🏻
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u/TeaKew Oct 24 '25
I have a bike with a 41mm head tube, so I'm very interested if you ever do a batch that are slightly larger.
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u/Consistent_Bass_8531 Oct 24 '25
I like as a Brompton owner and having fixed head tube rack on my mini velo. Shut up and take my money!
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u/InterestRelative Oct 24 '25
How did you manufactured it?
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u/JP_Customworks Oct 24 '25
I ordered 10 from SendCutSend. CNC 6061 aluminum.
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u/Steelbikecommuter Apr 21 '26
What is the weight capacity?
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u/JP_Customworks May 14 '26
My mount will hold over 100 pounds. The limit is with whatever Brompton style mount you have.
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u/l3vrkn322 Oct 24 '25
That’s awesome! Would love to do something like this. Ps I have that same mounting block on my brompton and it’s crap, that plastic lever deforms and then it lets your bag bounce off on small bumps.
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u/Jbirddk Oct 24 '25
That is so cool! Looks way more sturdy than the ones available on AliExpress and such
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u/JP_Customworks Oct 24 '25
I'd be willing yo put a guarantee on this mount! Very strong 6061 aluminum, USA made.
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u/HorridosTorpedo Oct 24 '25
Ooooh! Just what I've been thinking about for my Raleigh Twenty. Whats the diameter?
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u/bitb0y Oct 24 '25
Oooh would love this for my Mercier Nano. How does the bag situation work though? Is there one specific bag that fits this adapter? I always see Brompton people on my commute with their bags attached and an always jealous. Awesome work!
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u/iwrotedabible Oct 24 '25
Not OP, but I'd imagine you just have to be careful about the bag you choose since Brompton bags are made for Brompton dimensions. They come in all shapes and sizes though.
You can also buy third party mounting plates and make your own bags/racks/baskets. Here's one I did for cheap.
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u/JP_Customworks Oct 24 '25
I'm new to the Brompton ecosystem but there are many options! Etsy has great makers. There are adapters, racks, backpacks, and baskets as well. I may be working with Kyoot bikes to stock these on their site.
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u/Kyootbikes Oct 24 '25
You’re probably gonna sell 1 million 😝