Thursday, February 11, 2021


Brompton Accessories #25 - EZ Hinge Clamp Spring

 You are at - Jotaro's Blog / AhPek Biker / Bikes & Accessories / Brompton Accessories #25 - EZ Hinge Clamp Spring
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EZ Hinge Clamp Spring

Many don't realize it, but for the Brompton bicycle the hinge clamps is one of the most important part of the bicycle. It's that part that screws in and clamps the hinged part of the bicycle together - one at the main horizontal post and the other at the handle bar vertical post. Without these two clamps to lock the hinged parts together, it is impossible to ride the bike. I once had a nasty fall just because I failed to to tighten one of the clamps adequately!
Some, having lost their clamps, had tried to lash the hinged parts together - but often these are futile efforts that may last only for a short while. The thing about these clamps is that when loosened they tend to run out from their required vertical or horizontal positions, and also have a tendency to rotate while tightening, thus slows down the screwing process.

Some third-party suppliers have come out with ingenious accessories that solves this problems and keep the clamps always at the required position. One such accessory is the Titanium Hinge Clamps from Brompfication. It's a beautiful piece of engineering with spring loaded screws, and clamps that has one side shorter - the spring maintain the clamp at the required parallel alignment with the hinge, with the long side lock into position to keep it vertical, while the shorter clamp is just away from the bike stem to allow folding. and keeps the clamp at just the right position so that minimum screwing in is required (about 5 to 7 turns) to tighten the clamp. For more details see this blog.
The thing about these titanium clamps is that they need some effort to bolt them in at the correct position using a nut on the inner side of the tube. I often keep my spare tube in the main horizontal post and this bolt interferes with inserting and withdrawing of the tube. Also I often travel by air with my Brompton, and before packing the Brompton for air travel,it is always wiser to dismantle the hinge clamps so that they are not damaged by poor baggage handling. And the effort and time to dismantle and re-assemble these titanium clamps in place correctly is often frustrating, especially if some friends are waiting to set off. With my frequent air travel, it came to a point that, I just forgot about using them and went back to the Brompton stock clamps!

So I had resolved myself to happily (in ignorance bliss, that is) fiddling with, and adjusting the clamps as I screwed them in and out at a speed that will not win any records for sure!
Then of late, these little gizmos kept on being posted on the net. These tiny things, having the profile shape like the Green Lantern's lantern, are 3-D printed polyurethane widgets that will help maintain the clamp in the correct position. It's a light (1 gram) widget, with two thick stub ends connected by two arms. Made with thermoplastic polyurethane (PU), it's durable and surprisingly can take hard knocks (as can be seen in the videos from the supplier at the bottom of this blog).
It's such a simple and very affordable item, one would have thought why it had not been made much earlier. These PU hinge clamp spring were designed and made by Steve Woods, who goes by the name of Gyrobot. As he puts it, he is "a full time Design Engineer, with many years of design experience in the following industries, Automotive, Aerospace, Nuclear Fusion and is now currently designing Bionic Arms for Open Bionics. By night, he is a maker, breaker, fixer and tinkerer of all things going by the alias Gyrobot. I am passionate about Engineering. I am the director of Gyrobot Ltd."
He is a generous chap, allowing people to 3D print this for themselves, or for others for free (non-commercial). And have designed and gifted this CAD model freely for this purpose only. It will be good to support him by getting it direct from him at his Buy Page; after all each of this clamp only cost £3.95, way much cheaper that many other designs in the market.

These EZ Hinge Clamp Springs comes in three colors - black white and red - and are super-easy to install and take out: just what I need for my air-travel with my bike. I got the red-colour ones as they are conspicuous to notice when taken out and won't get misplaced easily.

They are so easy to install when compared to other designs, just slot them in over the clamp screws before screwing back the clamps. Simple isn't it, even a techno-nerd (like the missus) won't get it wrong 😅. As can be seen above, the two stubs (with one at the hinge side and the other at the a clamp plate channel) keep the clamp in the required position. The two legs, which can take a fair amount of torsion keeps the two stubs parallel.

After that, just screw the clamps in until they are just in a "ready position" for folding and unfolding of the hinges. Photo above shows top view.

An isometric view of the same "ready position" shows the legs of the hinge spring in a semi-compressed state. From this position, it just takes another 5-7 turns to lock the hinge plates together.

Another photo shows the hinge spring in a fully compressed state, with the clamp fully screwed in.
Note: the above photos which only shows one hinge plate is for illustration purpose.

This photo shows the hinge plate clamped together, the PU hinge spring is inside and is not noticeable and does not hamper the clamping process.

Another photo of the EZ spring in the "Ready" position. These PU springs are surprisingly strong, super resilient and takes torsion well as can be seen in the following videos further below.

Another view of the fully compressed PU EZ clamp spring.
For more details & to purchase click on the following link:

Video showing the flexibility of the PU clamp spring and how well it takes torsion.

Video showing the strength of the PU clamp spring and how well it can take "hard knocks" even when whacked with a hammer!

Video showing the compressiblity of the PU clamp spring and how fast it elastically reverts back into its original shape.
Even if over time, the widget does get twisted/compressed out of shape, the can be "refreshed" by just dunking them into boiling water!
All these tests are good; but how will the PU plastic withstand degradation under the hot tropical weather here. We will see and I will get back on this after using it, several months down the road.

Related Blogs :

Brompton Accessories #12 : Titanium Hinge Clamps
An efficient and beautiful looking clamp.

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Brompton Accessories #14 : Mini-O Bag Packing Light & Tight

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