My carbon Milan 4.2 build

[Arend-Jan]

Hello @Arend-Jan what Type of Milling Machine do you use?

It's a Makera Carvera Air

I'm looking forward to receiving my new machine, that's a Nestworks C500 as with that one I can also cut stainless steel (the Carvera can't do that).

 

[Arend-Jan]

I´ve got thin stainless steel wire from those honeycomb frames.
Some of them are even a little bit jagged.
Perhaps you try these?
I can send you some if you don´t find some yourself.

That's really sweet of you to offer! But I'm leaving them in. See above pictures, I simply cut off where I don't like it and will laminate.

 

[Arend-Jan]

 

[Arend-Jan]

Turned out quite nice, I think. I only made 50 grams of epoxy, and didn't even use all of it, maybe used 35.
I'm sure I actually removed more, and the gaps are gone so I'm happy now
Laminated strips along both front sides of the front wheel wells, along the front of the bridge, and along the sides and around the front the rear wheel well

 

[Arend-Jan]

Now, I'll show the swingarm bearings and adjusters.
The outer M8 washer is in a pocket, so that even if the nut wouldn't be fastened enough, the axle cannot slide out of the plates.

 

[Arend-Jan]

Earlier, I shared a picture about how I thought I could add structural support from the aluminium plates to the sides of the 4.2 body.

But I noticed how little support there actually is. When pushing to the sides, the shell simply flexes and I was (clearly) not pushing hundreds of Newtons of force.

So I will be doing a different internal bracing structure to effectively connect and couple both aluminum side mounting plates. Will be more challenging to create, but it should result in a very stiff structure.

 

[AntoineH]

You may find a design used in the Alphas and Milan—or similar models—that provides rigidity and efficient force transmission.
It features an organically curved shape that derives its rigidity from its curves and has a large, circumferential flange. (photos from the Forum)

 

[Arend-Jan]

Besides the fact I need to screw towards the middle instead of towards the sides, I was actually trying to do a similar thing with this design:

Spread out the load over a bigger surface. And not yet visible there, but ribbing would have added some stiffness.
But, the sides simply provide so little support, that I now plan to do it differently.

By the way; the middle support of that singlesided swingwarm looks cool, but since the floor can flex up and down easily there, twisting loads due to hard cornering are not carried well at all. I do like the idler support structure crossbeam, that looks well-designed.
And the side-mounting boss can rotate fore- and afterwards relatively easily. It should better have a beam running in forward or rearward direction too. That's what I did in my Snoek, by the way. The flex in the body could be felt and seen... when loading the wheel sideways.

 

[AntoineH]

One example from the EvoK is the swing mount, which features four screws on each side and a plate with a bolt. A counterpart was attached to the wall.
What ist missing is an organically curved shape to spread the forces to a wider area.

 

[Arend-Jan]

Thank you for the inspiration.
I'm hoping to share my design later this weekend. It's taking shape as I work with foam board and cut blocks, while I also keep testfitting the seat, plan on the suspension and chain idler placement.

I'm integrating a proper stiffening structure with good storage solution, while still alowing good serviceability and cable management.

 

[Arend-Jan]

Actual Rohloff 27.5" wheel is now in the bike

The modified (front and rear edges cut) Quest seat in the position that allows me to fit in the bike as a passenger

Then this would be the position of the rear chain idler

The chain clears the swingarm (just), and the swingarm only just clears the body

 

[Arend-Jan]

I would have liked to put the idler closer to the swingarm, but then the chain will eat the swingarm.
And I can't lower the idler, nor can I lower the swingarm...

The reason I would like to have it closer to the swingarm is to have more clearance for the passenger seat to go a little lower, as it now only just clears the idler (in fact it already touches when I lie down on it, as the seat then flexes).

So I guess a ~1.82m passenger (me) simply really is the upper limit for my Milan 4.2, with this rather big 584 rear wheel and this swingarm.

 

[Arend-Jan]

I mention 'this swingarm' as a different swingarm design could allow a lower chain line (through the pivot instead of above), which could move the idler closer, and then an even lower passenger seat is possible.

 

[Eichi]

Could you use a smaller idler wheel?
In my GT de swingarm is covered with a bit of the soft side of velcroband to protect it whe the chain is swinging up and down.

 

[Arend-Jan]

Of course I could use a smaller idler. But I don't want to, for the same reason why I don't want to use a smaller rear wheel: efficiency.
I don't want to run a motor, so I want to maximize/optimize the sh#t out of everything

Velcro (or something else) will be used, yes, as the chain will swing/shake quite a lot when going over potholes.

Another reason (to want to) move the idler closer is that the suspension travel then affects the chain line less.
With the idler far forward the chain line will move further from the pivot axle as the bike is pushed down in the suspension (the drive chain wheel then moves up). With the idler close to the pivot, this effect is reduced.
A lowered (and less moving) chain line also reduces 'squatting': the effect that pedalling hard introduces a vertical pogo effect.

Ideally, you want the chain line just slightly below the pivot axis. Below it, the chain tension would actually want to lift the rear of the bike up, counter-acting the rotational inertia of a forward accelerating bike.

On motorbikes this effect is very pronounced, because of (much?) higher chain tension and a (much!) higher center of mass.

My Milan GT MK5 did show clear squatting effect when pedaling hard, I did not like that at all..

 

[Arend-Jan]

Let's see how deep the rabbit hole goes!

 

[Arend-Jan]

Blasphemy!

Yes... much better

Chain line dropped, idler goes forward by a lot:

And yes, I'm very aware now effectively killed almost all torsion-stiffness of this swingarm.
But I'm not done yet, don't worry.

 

[Charger]

Wouldn‘t it have been better to do the cut on the downside of the swing arm?

 

[JaRy]

I think it is a good decision to give the chain all the room it needs.

Just recently I removed the chain tubes on my Velomo quad with the chain now running similarly close to the carbon spring arms as the string was towards your swing arm.
I installed deflection plates out of 1 mm metal sheet to protect the carbon and I am not totally sold on this solution yet.
The rattling when hitting the plates is pretty loud and I was surprised how much the chain is flinging up and down without the tubes even under tension.
I'd imagine in the velomobile the sound would be pretty bad and any piece added to the swing arm would wear out pretty quickly.

In my case removing the chain tubes was definitely worth the effort.
I am thinking about exchanging the plates with printed exchangeable protective pads now that I know where exaxtly the chain is reaching.
It is not really swinging sideways, so your cutout doesn't seem too narrow, at least from my limited experience view.

 

[Arend-Jan]

@JaRy Thanks. I also think this should be enough room. Especially since the idler is now really close.

Did 2 layers of glass isolation for the mounts.

And the initial carbon layers for the swingarm.

Quite annoying/difficult to keep it to stay down. But more tape always works