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 A carbon fiber fork chop 100mm to 142mm thread
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/24/2021 :  04:28:04  Show Profile  Reply with Quote
Today the fork is jigged and clamped.



A bit apprehensive at this stage.

Day 1

1) Cut just above the brake disc mount with 32tpi hack saw.

2) Bridge gap with carbon fiber plate epoxied.

Day 2

3) Smooth the transition with epoxy/microbaloon filler.

Day 3

4) Sand filler transition.

5) Wrap 2 layers of 480g carbon fiber twill.

6) Consolidate with 1 layer 12k carbon fiber tow.

7) Vacuum bag.

Done.

I also need to sort out derailleur hanger, I have an aluminium one but it might not work well for FWD.

Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/24/2021 :  18:25:17  Show Profile  Reply with Quote

Ouch!

Spread.

PVA on glass for carbon plate.

Roller

600w gravity press.

The plate is 9 layers of scrape 200g carbon fiber. I will see how thick that is tomorrow.
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/25/2021 :  02:32:55  Show Profile  Reply with Quote


I have moved fork legs exactly 21mm outward on both sides. Added some extra clamping arms to compress the fork legs in at the cut.

There is a small space for the carbon plate which should be ready to use tomorrow.

I am confident with the alignment.

My disc brake caliper has side to side adjustment so disc brake mount alignment should not be a problem if it is off.



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Balor
human power supergeek

Russia
1235 Posts

Posted - 11/25/2021 :  05:44:32  Show Profile  Reply with Quote
well-documented project, well done. Very interested what will come of it.
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/25/2021 :  22:36:15  Show Profile  Reply with Quote
It's going well so far.

Plate success! About 2-2.5mm thick as expected from 9 layers of 200g carbon fiber scrap. It is quite stiff in bending but pliable in twisting due to the fiber orientation which is interesting.

I checked the angle of the fork and it was off by 3 degrees! Now it should be much more accurate.

Paddle pop stick, rubber band clamp idea came to my last night and it works great! Cardboard template.

2 piece of carbon plate, it is manageable with the hack saw.

Surfaces roughed up with 80 grit and plates sanded to fit. If one rubber band is good than 3 is better!

Carbon fiber fillings won't go to waste they will be filler.

Carbon fiber filler and epoxy. Dollop it on the top and the epoxy will find it's way around the gap. It may be a good idea to block the holes so stop excess resin settling inside the fork.

Microbaloons added for more viscosity.

Now I wait until tomorrow. This is going really well so far!

Edited by - Third Wheel on 11/25/2021 22:39:34
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/27/2021 :  02:13:10  Show Profile  Reply with Quote

2mm off centre. I can fix that by raising the brake side drop out. I was worried the fork would be too fragile to fit to the wheel but the epoxy was plenty strong for a test fitting and a good idea to test fit!

The fork was exactly 142mm however the wheel has a gap which means I might actually have a 135mm width wheel! I should have meassured the wheel hub.

Sanding down filler. Random orbital sander with 80 grit, no problem.

Fork back on the jig, I have changed the fork spacing to 136mm.

Micro and epoxy, smooth transitions for the carbon fiber. I don't know how thick the transition should be so I've made it thicker.

Filler, different angle.

Filler, different angle. The micro and epoxy felt like play dough which was fun to shape.

Edited by - Third Wheel on 11/27/2021 02:15:07
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/28/2021 :  03:27:30  Show Profile  Reply with Quote

Smooth.

Sanding micro is easy and satisfying.

I decided against vacuum bagging to save the hassle.
I decided against wrapping with carbon tow, due to the tight space.
I used cloth tape by mistake I was support to use electrical tape but could not find that and used this stuff instead. I cut 50mm take in half to get something usable.

The tape is compressing perforated plastic and breather cloth to soak up excess resin.

I will see how it turns out tomorrow.
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/28/2021 :  23:25:52  Show Profile  Reply with Quote

This layup worked, two layers of 480g carbon twill.

The top layer of carbon fiber moved out of position and folded onto itself. Not ideal.

Looks good.

Problem 1: The disc brake caliper is too far to the out side.

Solutions.
1) Offset the brake disc using washers.
2) Cut the brake disc mounts and glue it in the ideal position.

I will try offsetting the disc with washers. I will need a special 6 point star screw driver.

Problem 2: When the quick release is tightened the wheel drags when you turn the cassette. Quick search says the "cones" are too tight and need adjusting, or the bearings are "shot".

Solutions.
1) Get bike mechanic to look at it.
2) Get advice from people online about the problem.
3) loosen the quick release to the point that the wheel turns freely.

I will do 1 and 2.

Edited by - Third Wheel on 11/28/2021 23:31:05
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warren
human power expert

USA
6777 Posts

Posted - 11/29/2021 :  14:00:26  Show Profile  Visit warren's Homepage  Reply with Quote
Lots of work! That should do it. Those forks are hollow and the layup you did will certainly be stronger than the fork itself. I had to add a couple washers behind the disk brake too when I changed my front fork to FWD. You may need to get some longer bolts to hold the disk on too.
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SpiderMonkey
recumbent guru

USA
963 Posts

Posted - 11/30/2021 :  08:45:30  Show Profile  Reply with Quote
Looks like a good start on that fork. I have 4 of the same. A few hard-won tips from someone whose made lots of mistakes over the past couple years:

Get some unidirectional cloth for spots like this. Half your cloth strands here are wasted running circumferentially around the fork tine axes. (If this was a hollow spot, they'd held avoid crushing, but since it's solid underneath, they don't help you out.) The uni would give you much higher stiffness and strength at the same mass. More than 2x (since it's usually heavier cloth to begin with, and often higher quality)

The excess resin and associated sliding is a result of using the "breather" and insufficient compression from tape. In the future, you'll get a much denser result by avoiding breather entirely. I made the mistake of thinking I needed it for my earliest wraps, and it was a hindrance.

Simplest solution for wrapping is to use PVC electrical tape, sticky side out, and wrap tightly. First wrap is right on top of the cloth. Then perforate with a pin. But one layer isn't enough.

Wait a few minutes for the weeping to start, and note where you have bulged tape. That's your overly resin-rich areas that need more attention. Make sure to perforate those. Try pushing out the resin with your gloved thumbs. Go ahead and wipe off the excess resin at this point as it will make the next wrap better.

Then re-wrap (opposite direction for your spiral). If you really want a "breather," you can wrap a single layer of regular paper towel between these wrappings to get better utilization of the first set of holes . It will stick nicely to the reversed tape. After re-wrap, perforate again.

I get by far the best results by using 2 to 3 primary wraps. Hardware store green cling works best if the shapes are larger. Here, the tighter bend recommends electrical for at least the first wrap.

I keep salvaged thin, closed-cell foam around for a final compression equalizer. Since all wrapping produces localized pressure differences and potential pooling, a final wrap over a couple layers (5-10mm) of foam spreads the compression more evenly. That comes to 3-4 wrappings.

With such compression (using cling as a first layer) I usually get evacuation of excess resin to the extent that the weave of the cloth is palpable. When weighed, those composite parts or additions usually match and often exceed the resin/cloth ratios expected from vac bagging as specified by my materials supplier.

--SpiderMonkey

Edited by - SpiderMonkey on 11/30/2021 08:49:27
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SpiderMonkey
recumbent guru

USA
963 Posts

Posted - 11/30/2021 :  09:06:00  Show Profile  Reply with Quote
As for the cones being maladjusted, that's typical for every new hub I've purchased over the past half decade or more, even higher-end Shimano XT stuff.

The cups and cones need to be adjusted well, or they'll be destroyed quickly. This means they actually need to be very slightly "loose" before you tighten the QR. If they're not, they'll be too tight after compression.

And you need to be able to get it right on your own, because shop mechanics often do not. My catrike was delivered to me with an improperly adjusted rear cup/cone and it destroyed itself after a couple thousand miles and I didn't notice it until 3 days before a big tour.) This is enough of a PITA to get right that I made a few parts to help me achieve it.

Park's excellent overview of the subject is here: https://www.parktool.com/blog/repair-help/hub-overhaul-and-adjustment

My video on how I sense the right amount of play is here: https://youtu.be/FAFwXG36cr0

Note that it is not about the feel of smoothness, but rather detectable rocking/knocking, and getting the right amount so that it just disappears when you clamp the wheel in.



--SpiderMonkey
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harv
recumbent enthusiast

438 Posts

Posted - 11/30/2021 :  15:11:08  Show Profile  Reply with Quote
I had a set of third hand wheels with Campy NR hubs. Once they were adjusted and I tightened the nuts, there was no compression from closing the QR with the axle in the dropouts.
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 11/30/2021 :  23:41:41  Show Profile  Reply with Quote
I asked the bicycle mechanic about the hub issue and he told me there may be some sort of part that is missing from the hub that is causing the problem. He did not think there as a "cone" problem.

He said I should reposition the disc so it is not touching the frame and then come back so he can see about the hub. I also noticed he had made a tilting trike front fork in his shop which was interesting.

I will cut the disc brake mounts and reposition them inward with the caliper tight on the disc. Glue it in a better position.

I was worried the front wheel was no good but that looks like it is not the case.

Edited by - Third Wheel on 11/30/2021 23:42:17
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Larry Lem
human power expert

South Sandwich Islands
2547 Posts

Posted - 12/01/2021 :  10:19:14  Show Profile  Reply with Quote
I've seen 135 mm quick release drive hubs and I've seen 142 mm thru-axle drive hubs but I've not seen 142 mm quick release drive hubs. Also, we're all happy that your clamping of the steerer tube to maintain alignment worked out. None of us could understand how the clamps worked from the photos (It certainly isn't necessary that we know everything.)

Larry Lem
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 12/03/2021 :  05:35:50  Show Profile  Reply with Quote
quote:
Originally posted by Larry Lem

Also, we're all happy that your clamping of the steerer tube to maintain alignment worked out. None of us could understand how the clamps worked from the photos (It certainly isn't necessary that we know everything.)

Larry Lem



It can be hard to know what other people don't know if something is not clear please ask.

Regarding the wooden jig, it has proven to be a successful hack job.

quote:
Originally posted by warren

Lots of work! That should do it. Those forks are hollow and the layup you did will certainly be stronger than the fork itself. I had to add a couple washers behind the disk brake too when I changed my front fork to FWD. You may need to get some longer bolts to hold the disk on too.



Out of curiosity how many layers have you used on your widened carbon fiber forks?


The start of the derailleur hanger. I have heard about galvanic corrosion, if that happens I'll make a full carbon fiber derailleur hanger.

Ouch the brake mounts are being relocated inward. Carbon fiber is easy to workwith.

What's what it looks like inside.

Here I am deciding how far to move the mounts inward. I make certain the mounting bolts are central on the brake caliper to allow the mechanic proper adjustment.

You'll notice two special tools, the wooden clamp (finicky you need to drill holes so it can grab the brake) to hold the brake caliper closed against the disc for alignment. Also the popsicle stick holding the brake mount gap open for epoxy application by preventing the wheel rotating.

Once the epoxy is applied to the surfaces the popsicle stick is removed and the wheel rotated perfectly into position.

Next up will be some minor filling and carbon fiber layup for a secure disc brake mount. Also derailleur hanger construction and mounting.

Edited by - Third Wheel on 12/03/2021 05:42:29
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Third Wheel
Starting Member

Australia
36 Posts

Posted - 12/04/2021 :  04:50:11  Show Profile  Reply with Quote

I wrapped carbon tow around the joint, generous application of epoxy.

I tied the carbon fiber plate to the aluminum derailleur hanger, secured it into the drop out to mould the hanger to the fork.

I wanted the hanger done today so removed the masking tape and glued the hanger directly to the fork.

Another view.

Epoxy hardens.

Another view.

Another view.

Disc brake alignment solved.

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