jfouellette

I was looking for some additional carrying ability. The installation went well. I added some temporary metal extensions to the struts so they could reach the eyelets on the fork. Note the black silicone hand brake covers for the cold metal.

Ron Damon

It would appear that you and Pinigis belong to the same Utilitarian über Alles school of design and relish in a similar "aesthetic". Holy cow!

Duragrouch

First, silicone, not silicon. One is for chips, one is for... implants.

Second, your double-long-plus-extension front struts, may buckle under load, due to excessive "slenderness ratio" (real term) respective to the cross-section and unconstrained length. You may need to use circular or rectangular hollow section. If you want to calculate before buying material, that can be done. But it will be different for steel versus aluminum, as the latter has 1/3 the elastic stiffness, which is a critical factor for buckling columns.

Also, the following works dandy for small-wheel bikes, as it fits the same distance above the wheel as the 26" or 700c wheels it was designed for (because bolts to the v-brake studs, same distance with respect to rim) but is perfect in scale to the small wheels. Used to be called a "sixer", perfect size to hold a 6-pack. Used to be $10, now up to over $20:

https://www.amazon.com/Sunlite-Gold-...dp/B002MKHR6G/

Jipe

My experience based on several small wheels bikes (Brompton, Birdy, Moulton, Tern) is that its much better to attach the front bag or carrier to the head tube (so that it part of the main frame and independent from steering) than to the handlebar.

The best is to adapt a Brompton front block that accepts up to 10kg.

You cab do that with your own mounting adapter or buy some (strong but pretty expensive) adapter (if the diameter of your head tube is in the range): https://www.valeriasbikeaccessories....-tube-etc.html

jfouellette

I agree. I m a practical person. I m working on a good looking bike.

jfouellette

Good to know. The second option I already had. It didn ´t work for me. Thanks

They are working on silicon chip implants.😀

jfouellette

very true. I have this on my Brompton clone and it’s very stable.

Duragrouch

(above) Generally I agree that weight is best attached to the frame and not steered. However I don't like the cantilevered load of the front block racks (although, come to think of it, I did have a seatpost beam rack on my road racer for many years, but it held only a small trunk bag). That said, a small amount of mass that is steered, if ahead of the steering axis and mounted low, can improve stability on small-wheelers; a) adding a bit of mass and polar-moment damping, calming the steering, less "twitchy", and b) will tend to steer in the direction of falling, adding a bit of self correction, especially if the fork has a relatively smaller "trail".

Duragrouch

I'll have to remember that expression, from the little deutsche I know, I grasp the meaning. "I resemble that remark!"



By the way, those front panniers are hung off a "sixer" rack. I added a stick on each side between the forward top and fork dropout, to keep the panniers out of the spokes. The rack is rated for 40 lbs but I don't go anywhere near that for front loads, don't want to overstress the rack, nor effect steering that much.

Ron Damon

Deutsch, Grouch. No 'e' at the end when it's a noun, and capitalized as all nouns are in the language of Göthe, Mozart and Falco.


Germany in German (Deutschland) is very different from the English word for the country. Or in Spanish which is Alemania. Did you know that Koreans call their own country Hanguk? Or that in some languages Greece is Yunani and Egypt is Mesir?

Duragrouch

Thank you, my knowledge is very limited. I used to work with some Teutons (if that is correct), tried to learn some German, but one said, "Why? We're all learning English."

Long after that time, I heard of a big flap about a foreign choir, greeting visiting German dignitaries, sang the now-unused verse(s?) to great embarrassment.

Ron Damon

Learning German is "what eternity was made for."
- Mark Twain

The language is a royal bytch with its three genders and four cases. Be glad for English.

Duragrouch

I couldn't stand trying to memorize masculine and feminine nouns in French. I think my choice of college foreign language was best summed up by the title of the David Sedaris book regarding being an ex-pat living in France, "Me Talk Pretty One Day."

I have been told by foreign speakers that English is a good technical language, can better describe some things.

Jipe

The adapter of Valeria is very thick and strong but you are right, the load is more cantilevered than on the original implementation of Brompton.

But there are much worse designs, you will surely appreciate this one (and its not a joke or a photoshop modified image, its really sold like that):

Duragrouch

Yikes! My FEA eyeball does not like. It would have been so easy to have an upper clamp at the head tube as well, increasing the span by over 10X. What this tells me is, a) Zizzo did not do a careful design on this, so other original stuff of theirs may be suspect, and b) Their 20" aluminum folders are most probably reverse-engineered from similar aluminum folders by Dahon. NO, I take that back; Upon close examination, the Zizzo Liberte, for example, is missing some key corner gussets that Dahon added for their aluminum frames, that were not present on the original steel frame designs.

Fentuz

Aesthetic is one thing, mechanical integrity is another. I would be worried this thing break, it needs at least a top collar (like the bottom on on picture) to brace the lot to the head tube.

Duragrouch

Exactly. That's what I thought.

Jipe

There are many adapters like that with 2 collars, the first one was designed by Bikegang sold by H&H for the Birdy and as usual it was (badly) copied by Litepro but still with 2 collars!

Schwinnsta

Grouch, are you saying something here? What is a small amount of mass? For that matter, is a polar-moment different from an Eskimo-moment. I really can't tell if you are talking about loads on the carried by the steering or loads carried by the frame. I can tell you from first-hand experience that loads carried on a Brompton block handle different from rack mounted on the front wheel or fork, and you can carry more on the frame mount.

Schwinnsta

I don't like how they cantilevered the block, either. They did lower the limit to 15 pounds. There can be problems with both the add-ons and the ones that mount direct to the tube, and that is both with the location and the angle of the mount. The bag is too close to the handle bars.

Taking the bag off will be problematic. Also, not shown, and likely for a reason, is that the mount is too low to have a front light mounted to fork. Indeed, some bags may have problems clearing the fender. The picture is of the Forte that comes with the integral mount. Brompton has had a generation or three to get this right.

Duragrouch

This all varies for the bike. I'll try to explain.

Polar moment: Lets say you have a 10 lb sphere of steel. You can hold it in your hand and rotate it left-right without much effort. Now let's split up that weight to (2) 5 lb balls, each on the end of a 2' long pole, and assume the pole has no weight itself. So like a barbell. Now grasp the pole in the center, and try to rotate the bar (like a baton-twirler, not just twisting the pole along it's axis), harder to rotate, right? That's because, for the same weight, you have greater polar moment in the second example. (Porsche did this intentionally with the 928 design, putting the engine at the front, and the transaxle at the rear, to specifically increase polar moment, to make it a more user-friendly sports car, slow things down if the rear end starts to step out in a skid, even at the expense of performance, as sportier cars try to minimize polar moment.) Now, if you try to twist the barbell around the bar axis, the polar moment will be much closer to that single ball, in fact, it will be *lower*, easier to rotate, because you have put the weight closer to the center of rotation than with the single 10 lb ball.

Now let's apply this to our small wheel bike steering: My front panniers, hung from a "sixer" rack, actually are about 1/3 behind the steering axis and 2/3 in front of it. A concentrated load, like a water bottle at the bottom of each, will be near the steering axis. 10 lbs of weight there will calm the steering significantly, make it less twitchy. However, if I put the weight on the top, extreme forward on the rack, I may need only 5 lbs to get the same effect, because the weight is further from the steering axis, so greater polar moment for a given weight. Also, the weight further forward will have more effect on the bike steering in the direction of falling (some consider this improving stability), than the weight that is closer to the steering axis.

How much the weight affects the steering, has a lot to do with how much "trail" (aka caster) the fork has; More trail gives more self-correcting function, but with too much trail, you get too much "wheel flop" when stopped. This is a problem with motorcycle "choppers" with very slack (laid back) head tube angles, for style, but this gives terrible steering dynamics.

I don't have a fixture to measure it, but I think the fork trail on my Dahon Speed 20" is small, I'd like more, and other folders like a Bike Friday I think do.

But some studies have said that even weight that is not steered (fixed to frame), but forward of the steering axis, helps stability (not in terms of damping the steering motions, but steering in the direction of falling):

https://www.scientificamerican.com/a...f-stable-bike/

And... call me Dura.

EDIT: In terms of stability, I agree, you can carry more on a frame mount than steered on a front rack. However, in terms of structural design to support loads, usually front racks supported by struts near the dropout, are much more able to support heavier loads, than the cantilevered from block. I think the earliest Moulton "shopper" bikes (not the space frame), had integral cantilevered rear and front racks attached to the frame, strong and stable.

Schwinnsta

Here is a picture of my Moulton, it's a 64 f-frame standard, and you can zoom in and see how the front rack is supported. Below that is a pic of a butcher bike I downloaded off the net. I would bet that the butcher bike can hold a lot of load. I would also bet that would be a ***** to pedal. But here's the thing. The moment arm on a Brompton block is small and until the block breaks or snaps off the ride will be the same. In terms of stability, loads on the Brompton block will act the same as loads held by stronger set-ups. They are all supported off the frame. They will all ride similarly. The block is just as stable, till it breaks or the tension screw at the tops pulls out



or it snaps. The block works because the moment arm is small. The shoppers will have larger moment arms on the frames.

​​​​​​​Moulton space frame racks are supported similarly as the f frame.

Duragrouch

(above) I agree with all of the above. Thanks for the detailed pics. The bottom front frame attachment on the silver Moulton is *exactly* how I would have engineered it, the lateral bolt is in the middle of the beam and the neutral axis in bending, very sound, doesn't weaken the beam. That first Moulton showed a lot of thought in improved utility, that was a great bike, and I've read, very widely used (at least in the UK, I'd never seen one until recent years online). I've also read that after the design was acquired by a larger company and cheapened by eliminating the rubber suspension, the frames cracked, as they didn't realize how much shock (peak) loading it absorbed.

jfouellette

Update: The steering is more controlled when there is weight in the front basket. I bought two bottles of red wine and placed them in the rack. The difference was noticeable.

Duragrouch

Mimics my experience as noted in post #8; clip-on aero bar with a water bottle on it, low rack with panniers.