Engineering bicycle part by part

[Komarov]

Hi everybody!

My name is Ivan, I'm 25 (update: was 25yo) yo and live in Moscow, Russia.
I'm engineering and manufacturing the bicycle parts for a living Most of them end up being quite lightweight despite that the main goal is function and strength, but its just the property of well engineered composite

I'm slowly creating more and more different parts for a small bicycle brand that I co-founded and as outsource engineer for other clients. I hope to make my own frameset one day, so I figured that I'd share some of my work here to discuss because you cant get a proper oldschool holy war about bicycle stuff in places like instagramm and the truce is born in a dispute, so here I go.

I will try to tell something interesting about development and features of my recent work and because I'm an engineer I will bore everybody to hell with technical things. But good for me that every self-respecting cyclist already have a PhD at least in mechanical engineering, carbon fiber, metal alloys and theoretical physics so it will be a peace of cake for most of you.

To catch an attention I'll start with simple but very complex part as a bottlecage, here are the photos that I stole from our web-site:

We decided to make the cage open from the top to match all bottles because it turns out that they significantly vary in diameter.
But here came the problem: all carbon cages I've seen has thin and wide "wings" which hold the bottle in place (they are relatively easy to make because you can use elastic silicon mandrell).
It didn't seem to me as a proper decision because narrow but thick "wings" would be much stiffer due to the higher moment of inertia of a cross-section (ok, here we go with technicalities). But how tf should I mould them?

Firstly I've bought a manual rotational axis for the cnc-mill (cost around 300$ )

And somehow I succeded in making the metal mandrel-part of the mould which you can see in the middle on the photo below

Then I've tried to make a cage pressing prepreg against that mandrell by vacuum couple of times. All turned out with really bad surface quality but usable non the less.

Couldn't sell them like this so after couple of monthes of drinking vodka with borsch (national russian soup, you should really try that one) and fighting naked with bears in the snow I've came up with left and right metal parts on the photo above.

Here is when the quality started to become at least sufficient. the weight turned out to be 21 grams (I knew it from the CAD model)
I've made a tooling to make the rear cutout in the cage by cnc mill so the holes will be exactly the same and straight:

And then, when we finally managed to get a parts with the surface quality, compaction of fibers e t.c. that I'm quite proud of.Then we put 1 part in crazy russian nuclear-multiplying machine to make some more

(going to Indonesia in monday)


So here is the story how I've made a bottlecage (really proud of that one). Many people said that its the stiffest cage they ever tried (for an open one) so it seems that idea behind the design was the right one.Hopefully I'll be able to say more about other parts if I wont die during the winter in my russian hut.

It's to late, the log in the burner already burned out and I hear the wolves outside the window. Thanks everybody who somehow managed to read to the end, hope I'll be able tell about other things I made in the future.

Feel free to ask questions and I'm very eager to know how you guys imagine the best bottlecage or any other part!

P.S. I also have insta account:https://www.instagram.com/smokytrain/

[MrCurrieinahurry]

Hey man! Welcome to weight weenies looks like some awesome products on your INsta.... What's price of the cages?

[Komarov]

Thank you for the welcome! My main idea was to post something interesting about once a week - I have quite a lot to share with projects both finished and in development.
Didn't want to just advertise what I do, but since you asked - the price for the cage is 70$ and 60$ if you are buying 2 of them

[synchronicity]

Interesting projects! Although a name like björn does not sound very Russian.
Was that intentional?

[Komarov]

Interesting projects! Although a name like björn does not sound very Russian.
Was that intentional?

Yeah, we disguise ourselves from mr. Putin and KGB so we are not sent in the Gulag as western spies

I'll try to keep projects interesting, so much is going on right now.

[synchronicity]

Well what would you call it if you had to use a Russian name? I'm curious.
I'm learning Russian by the way, have been for 3 years.

[Komarov]

Well what would you call it if you had to use a Russian name? I'm curious.
I'm learning Russian by the way, have been for 3 years.

Very forward thinking of you to prepare for russian world invasion before it begins

Jokes aside: "Bjorn" is the translated from russian part of my fellow-partner-co-founder's family name so in russian it would be something like "медведь на велосипеде"

[Yoln]

Awesome man! Thanks for sharing.

Looking forward to you next post talking about this incredible saddle !!!

Keep up the good work

[Komarov]

Hello there!General Kenobi

Since I've posted previous week I roamed weightweenies for a little and found a huge amount of questions about "what type of carbon fiber should the proper bike be made of". So I will try to explain the topic(since I didn't really like the answers I found) on example of the mtb handlebar I've designed (It can be the road one, it doesn't matter).

First of all a little spoiler and answer to the question: it doesn't really matter that much is it t700 or t800 or even t300:)

Warning!!! Everything below will bore you to hell if you are not crazy about carbon and stuff
part1:
To illustrate that genious thought of mine I'll show the photo below:

The strory behind the photo is simple. We were developing our own bar and wanted to break and cut some bars from another brands to know how much they can take. On the bottom is the early prototype which I moulded myself. It's not perfect, even has a little void, but in general it sustained the load around 400 kgs on 1 side what was very impessive to me. I didn't expect that kind of strength)
On the top is the bar from the brand which considered a good and reliable one among mtb riders (I'm not coming near their carbon components ever in my life). And that part isn't even the worst. Unsurprizingly the "bad" bar sutained the same load (but creaked when loaded so I doubt that it was able to sustain a cycle of loads - the cracks will prolong as it loaded until it breaks) because... It weighed 260grams vs 160grams of my bar

The point of the story - Doesn't matter if you use the best fibers in the world if you cant mould them properly. And it seems to me that its not an easy job for an asian production.

part2:
There are several ways the part can break (It can also break from the tensile load, but it seems thats not the case for concrete bridge pillars )

The concrete and steel is a composite very much like the carbon fiber and epoxy, so my picture is relatively relevant.

Almost the whole bicycle is basically tubes of different shape which are subjected to different loads. The frame of course isn't so simple as mtb handlebar, but the logic is the same.
Imagine that the circle on the left on the picture below is the cross section of the mtb handlebar somewhere in between the stem and the grips and some force bends it down applied to the end of the bar . And when the tube is bended it experiences the tension on the top of the tube and compression on the bottom (Also shear because the top of the tube is tensioned and the bottom is compressed).

I'm a microsoft paint God, I know, I know.

But carbon fibers have very impressive tensile strength so its very hard to break them on the top of the tube subjecting to tensile stress.
However its much easier to bend the tube so far that fibers on the bottom will buckle inside the cross section of the tube and the hole handlebar will break. (The bar will buckle on the bottom before breaking from compression because the wall of the bar is relatively thin and the moment of inertia of cross section is relatively low)

So in general: bars break from buckling not compression, shear or tension.
And when it comes to buckling - it doesn't matter so much how strong the fiber is when tensioned. Even more - so much advertised high modulus fibers may buckle even faster then cheap t300 because they typically 5 microns in diameter (single fiber) and t300 is 7 microns which gives them high inertia moment. Also High modulus fibers are crazy expensive, so the whole bike will cost like a fighter jet.

You may increase the stiffness of the bar by placing the high modulus fibers on the top of the tube so it will bend less and buckle under higher load, but shouldn't make all the bar from high modulus fibers. Also almost nothing will be gained by placing T1000 instead of T800 fibers on top of the tube since they have the same stiffness.
You can shave some grams by placing the right fibers in the right places, but it will not save so much comparing to the part just properly made from T700. My bars are made from T700, I admit - no bullshit marketing, just pure strength.

Alas with this engineering stuff, the point is - dont trust marketing stuff about high modulus T9000 fighter jet-super-duper-aerospace fibers, they only work in right places, save very little weight and god forbid someone who makes entire bike from high mod fibers.

And when we are back to the handlebars:

Thats how it should look like. No paint to mask the bad quality, just raw carbon straight from the mould. The same goes with the frames - look who isn't afraid to show unpainted parts.

To generalize my flow of thoughts: Look who and how made the part(everybody posting cuts of carbon components, right?), thats more important than some fibers grade they telling that they used. Bike made from T700 could be among the lightest in the world and cheaper than shitty frame made intirely from T1000 that will break as soon as you ride over small pothole.

I really hope someone will enjoy it! (Its doubtfull, but hope is still there my friends).
Sorry for my possibly bad english where you can hear russian accent just by reading the post.

[MrCurrieinahurry]

I love this!!!!

[Komarov]

I love this!!!!

Thank you!

[Maddie]

Me too, really like these insights!

[Daveke]

This is awesome!

[Komarov]

Hi everybody!
I wanted to write earlier, but I was busy with all new year celebration stuff and had lots of work on new moulds for bottlecages and TT bar extensions.

So guess it is time to finally tell a bit about the design of our saddles. I know that everybody are interested in padded ones from Carbon 3d,

but I am to be an asshole and will start with engineering behind both padded and just carbon ones since they share the same philosophy and there is a lot more than just 3d printed padding.
And a disclaimer for starters because following information might sound too opinionated like I’m a bit of a smart-ass:
I won’t claim myself as engineering guru, who knows better than every engineer designing the saddles. Not at all. I’ve had my “Oh shit, that’s not working as it should” moments, but it looks like I’m not completely dumb and hopefully gained some valuable experience and it seems that in the end I figured a thing or two about the saddles.

Now lets start.
Carbon fiber saddle with or without padding consists of rail and shell, both of them produced in separate moulds and have to be somehow joined together.
The strength of the core and the rail seem to be managed pretty well by majority of manufacturers, however I’ve seen a lot of saddles, especially carbon ones, where those 2 parts joined together became separated again
I did my part experimenting with joining the rail and a saddle and found out that conventional bonding is not as reliable as it should be. So I’ve come up with a know-how I’ve illustrated below (Please thank me that its not depicted in Microsoft Paint as usual – I’m developing new serious skills)

So here is traditional bonding between the core and the rail shown in cross-section:

Looks quite simple, but in real life when the core starts to flex (because everything flex) the bond starts to work not as it intended to.
Imagine attaching the stripe of Scotch (not the whiskey, the duct tape one - for those who are not over new year holidays) on the table. When you pull the duct tape in the direction parallel to the surface of the table(top left on image below) - you more likely to break the tape rather than to peel it of the table's surface. But if you pull it up - than it peels of really easily because you loading veeeery small surface area of the glue connection.
On picture below it would be the bottom left

Без названия.jpg (3.95 KiB) Viewed 4861 times

So when the shell of the saddle flexes - it loads the bond between the shell and the rail like in bottom variants on the picture above. And you dont have to be too much of a smart-ass to figure that its not the best way to go around this issue.

And now behold the monstrosity I've come up with

Actually the plies are very thin so it looks quite elegant in real life.

The point is that you have to lay additional carbon plies around the shell and the rail creating the hollow socket in wich rail will be inserted. Basically those plies are wraped around the whole structure while beeing moulded simultaneously with the core. After the rail is inserted the space left in that socket is filled with glue under pressure - pushing out the air bubbles and almost welding the parts together. I really tried to destroy that bond and couldnot detach the rail from the core even with help of diamond dremel disc. I ended up completely destroing the structure while almost cutting my fingers off due to my arms inconveniantly growing from the ass, but could not tear the rail from the shell.

The other feature I introduced in the cores of the saddles is reinforcing them with longerons.Thats the simplest thing you've tought the first when studying the strenth of materials in uni and I'm sure other manufacturers do it also placing more ud material in the shell in different places, but it adds relatively minor improvement due to the small height of those reinforcements. I guess Specialized did something like that with their Power saddles, but i'm not sure it was not mostly cosmetic and then they got rid of that feature.
So here the example of what you have to imagine as the cut of 2 different saddle shell's.

The amount of the meterial is equal in both of them. However, when you measure the inertia moment wich greatly defines the stifness and the strength - you will see more than 2 times difference.

Here is the photo of saddle from below:

You can see the reinforcement in the rear which not only greatly contributes to the cores strength but also creates sockets for the rail in the rear part of the saddle.
To do that you have to make moulds far more complicated and I think it doesn't work for everybody because of the additional labour cost and complexity of production.

Summarizing all information above and combining with proper moulds for the rails and a shell wich allow to apply the pressure around 80bars comparing to only 1 bar in vacuum infusion technology that is widely used for saddle shells - it seems that I'm a bit of a smarts-ass after all and created something quite technologically advanced here))
But all this is minor when we'are speaking about tech that Carbon 3d use to print the padding (you can look on there web-site https://www.carbon3d.com/ since I'm tired typing on my typewriter that someone can call a notebook).
Hope that I wont be too lazy and finish the talk about the saddles next week) Thanks everybody and have a good weekend!

[MrCurrieinahurry]

What's the weight?