www.recumbents.com - Starting the Kid CF bike
www.recumbents.com
www.recumbents.com
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
 All Forums
 www.recumbents.com
 Technical / Bike Building
 Starting the Kid CF bike
 New Topic  Reply to Topic
 Printer Friendly
Previous Page | Next Page
Author Previous Topic Topic Next Topic
Page: of 5

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 01/26/2019 :  16:03:22  Show Profile  Reply with Quote
Bah. Must have measured poorly, or made another error. Ferrule came out 46.4 mm OD, not too wrinkly. Looks like I'll have a lot of sanding to do to get it down to 45.9-ish mm. In my experience with this material, it's usually ended up close to or thinner than the dry measurement after I've wetted it and squeezed the heck out of it. Not this time somehow.

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 01/27/2019 :  09:56:55  Show Profile  Reply with Quote
Well, I think my screwup turned out to be a good thing. The too-thick main tube ferrule meant I had to do a lot of sanding to get it down toward the 46mm OD I needed for it to fit well into the 50mm main tube. It measured about 46.5mm in most places. It was also wrinkly as hell. After all that sanding, no more wrinkles, and a nice, smooth sanded surface for bonding.

I told my wife not to worry. I'd been training for this task my entire life!



I had to head to Home Despot to get some more aggressive paper though. 150 grit was not going to get the job done without generating some carpal tunnel syndrome. I went at it with some 80 grit for a while, and then moved back to the 150. The weigh-in beforehand.



And afterward.



Good thing I didn't go by measurement alone. I had my digital caliper and started trying to shove the ferrule into the main tube once I got near 46.1mm. The ID of the tubes is supposed to be 46mm, but it is, of course, not *quite* that. The tube started sliding in at about 46.1mm, actually, so I just worked the parts where it bound until I got a nice tight fit. Using the average from a bunch of spots measured with my digital caliper, the OD of the ferrule is now about 46.05mm, and the ID of the main tube (I can only measure at the end, yeah) is about the same. It slides in without binding, and can be wiggled a tiny bit. I can only tell by feel, can't see much.



Fits into the tube nicely.

Can you spot the seam when I put another one on the other side?



--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/12/2019 :  14:16:53  Show Profile  Reply with Quote
I got the main tube cut to the right dimension. I added 3cm of length to the bike since the kid is growing quickly and I figured an extra 3 cm of wheelbase couldn't hurt.) I mixed some epoxy + some of my carbon dust and it went black like oil but was still pretty thin, so I put in a little fumed silica to thicken it from warm maple syrup up to chocolate sauce on the thickness scale. I was uncertain I'd get any bondline spacing from the dust, so I put in very little bit of glass bubbles. I smeared it all inside the prepped tube and then all over the ferrule, then carefully inserted. It felt a little grainy and took a little twisting to get nicely into place. Checking from the back side I could see I hadn't outrun my glue, and I had a bead of excess built up in front. I think it's probably going to stick just fine in there. After sanding the smooth out of the inside of the main tube with 120 grit, I had a tiny bit more gap, but it was still pretty tight.





https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=570019&v=s

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/13/2019 :  07:21:38  Show Profile  Reply with Quote
Good thing I added 3cm to the bike length. I measured my kid's x-seam last night and it was 3cm longer than a couple months ago. That seemed impossible, so I measured again, and there it was. They grow in some crazy spurts.

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/14/2019 :  20:57:24  Show Profile  Reply with Quote
It's finally starting to look bike-ish, or recumbent frame-ish anyway.



I have decided I can use superglue alone for tacking mitered angles which are pretty much flush. I tacked the last join with it tonight but my basement table turns out to be crooked. Checking the bike against the granite countertop upstairs (the flattest surface in the house, I believe) showed it to be crooked by 1.5mm. Can't have that, so I retired to the garage to crack the tacked join apart and redo. I could not do it. Not, at least, without resorting to leverage and force which I thought would damage a tube or two. Soaked area in acetone. Nope. Finally had to cut it apart with a diamond wheel, resand, and tack again. This time on the granite countertop. Living dangerously on Valentine's Day.



Looks like this one ought to meet my goal of being suitcaseable. These are the longest dimensions of the setup, and they come in around 24-25 inches.



--SpiderMonkey
Go to Top of Page

warren
human power expert

USA
6470 Posts

Posted - 02/15/2019 :  08:02:32  Show Profile  Visit warren's Homepage  Reply with Quote
Looks great! That should be light enough for your daughter to lift and carry herself!
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/15/2019 :  13:41:30  Show Profile  Reply with Quote
She's skinnier than I am! My spreadsheet estimate is for a weight of around 23 pounds before fenders (but including pedals). I don't think I'm forgetting anything. I'm pretty sure it'll be under 25, which seems like a pretty good weight for a disc brake bike that separates.

Now I just need to make it work!

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/16/2019 :  16:43:10  Show Profile  Reply with Quote
I laid up carbon on the lower of the 2 140-degree angles in the frame. I figured I should shoot for somewhere around 2mm of fabric around the joint. That would have been about 12 layers of plain 3k, but I used some heavier unidirectional on top and bottom of the joint a couple times, and 2 45 degree sleeves. After it was no longer tacky but still rubbery (below) I measured the diameter at about 53.25mm - 53.7mm. I then put on a couple more patches of unidirectional top and bottom, a couple patches of plain 5 oz 3k on the sides, and another sleeve. Probably overkill.



https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=570245&v=1o

I ended up doing the following layers. (Side patches were 60mm wide 80mm long at first, then 60mm long. Top & bottom patches were 40mm wide and 80mm long at first, then 60mm. Uni patches were 80mm long, 1 inch wide. Braided sleeve was 1.5" nominal, about 90-100mm long when pushed wide enough to fit.)

1 layer: 11oz unidirectional, top, bottom, left side
1 layer: 8 oz braided sleeve at 45 degrees
2-3 layers: 5 oz plain weave layer (1 layer = 4 patches, top, bottom, sides) Can't remember if I did the two or the 3. Leaning toward 3.
1 layer: 11 oz unidirectional top and bottom
1 layer: 8 oz braided sleeve at 45 degrees
***partial cure***
Then hot layer (see narrative below) layers:
1 layer: 11oz unidirectional top and bottom.
2 layers: 5 oz plain weave
1 layer: 8 oz braided sleeve
1 touch-up patch on bottom, 5 oz plain, where braided sleeve looked ugly

--SpiderMonkey

Edited by - SpiderMonkey on 02/16/2019 16:55:50
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/16/2019 :  19:54:56  Show Profile  Reply with Quote
The layup on the first bend added 50g. That was about what I estimated, maybe a tad more. This being my first rodeo, I'm not sure how much CF is needed on these joints. I'm erring on the side of caution -- I think at least. I figured 2mm around the outside made sense, and that's about what I've got.

Frame weighs 1106g right now. That's nearly exactly what I thought it would be at this point. Should come in around 1,300g once I get the pinch assemblies on. I suppose the idler mount and plate will add a bit.



I got the jig squared up. I will probably knock together a quick frame alignment tool tomorrow since I've got some nice straight pieces of MDF that my treadmill replacement deck was shipped with, and I bought a few carriage bolts and wing nuts. Sure looks straight, and if all the uprights are as plumb as the angle finder says they are (everything checks to within 0.2 degrees or better) then the alignment tool is probably not necessary. But I'd rather worry once.



Upon measuring, the bike's fit range encompasses current daughter dimensions as well as current wife's. Wait, that came out sounding bad. Anyway, it would fit either one of them is the point. The kid will be seated much further forward, boom all the way in, but I think the weight distro will still be fine. She won't know any different and she became a pro at handling her current LWB very quickly, so I figure it'll be good.

I'm thinking I'll cut in the head tube next, since a lot of the layup for that will be right next to the layup for the joint up there, and I might as well do those at the same time. I'm nervous about getting that head tube in there right.

The plan is to use my paper pattern, cut the rough hole, abrade with Dremel to indicated size, put in head tube, squish in headset, insert fork, check for my 69-degree or 70 degree angle (That should yield around 55mm of trail on the fork, which has 33mm offset) and check to make sure it's plumb, then tack, fillet, and go.

--SpiderMonkey

Edited by - SpiderMonkey on 02/16/2019 19:55:30
Go to Top of Page

Jeroen s
Starting Member

Netherlands
13 Posts

Posted - 02/19/2019 :  12:32:24  Show Profile  Reply with Quote
Hi Spider monkey, This is looking great.

For minimum boom insertion 2x the boom diameter is a often used secure measure. If i where in your position, i'd enlarge the overlapping area with a longer final layer. Mabe also think of how and where to mount the idler. The thickness is probably right.

If the headtube angle is a degree off forward/rearward, that is not a problem, the bike will still be ridable. If its off left/right that might be a problem. one way to check that is to jig the bike up with the fork in the normal position, and then with the fork facing rear, 180 degree turned. in both setups the dropout should be 50 mm from center.


Another thing is that the current jig tilts the frame compared to its real position with wheels mounted. Make sure u get the angle right, in the position it would be with mounted wheels!


I would not worry to much about weight distribution. In percentage the daughter would get more on the front wheel, in kg it might be the same or less than with the wife on it. Most lwb bikes would get far less weight on the frontwheel then u have on the rear. It might be that the girl would lift the rear wheel under extreme braking, but even in that aspect weight distribution would still be better then on an upright.

If u can find a straight tube with an outer diameter the same as the inner diameter of the head tube that might be easier then using the fork and headset. I am pretty sure that i would mess up things and get epoxy on headset or fork. I used a 30 mm alu tube with a 1 inch to 1 1/8 headset adapter to get the final diameter. A headtube for a 1 inch fork is 30 mm inside.
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/20/2019 :  18:00:14  Show Profile  Reply with Quote
I finally got my jig nice and straight all the way to the front. I'm glad I obsessed and built myself an RCFAT (Really Crappy Frame Alignment Tool).



It was enough for me to discover that what looked straight was, after about 1300mm, off by about 8mm. No good, that. It took some time for me to figure out what to use to get things straightened up and how to mod my jig uprights, but by the time I'd stared and sworn enough, things look like they're within about 1mm. Hard to tell for sure because the RCFAT is a little flexy, but since I'll be doing the head tube by fork 'n' dummy axle, I think I'll be good.



I put the dropouts on the floor and grabbed the front of the main tube and put my foot in the middle and stepped + yanked as hard as I could and couldn't detect any flex, so I think the layup so far is close to adequate. I'll give it some sitting and bouncing once the head tube and fork are in to see if I need to add any carbon right away.

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 02/24/2019 :  12:41:57  Show Profile  Reply with Quote
I figured I'd worried about this long enough. I made a better, aluminum frame alignment tool and that showed my frame was within about 1mm of symmetrical front to back, which I figure is as close as one can measure, and probably close as I'll get. Tiny alignment tweaks, if necessary, can be made from there with dropout modification.



So, with thumping heart, I cut open my tube after transferring my miter pattern on with pencil. I checked against the full-length head tube to make sure I was roughly in range, and then decided how long to cut the HT. I must have measured the fork wrong because I ended up needing 1cm more in HT length than I thought. Rest of bike measures exactly the way I wanted. (I was within 3mm on my wheelbase estimate...) Then I cut and squared the head tube using another tube squaring tool I bodged together. The Origin8 cups press in with just muscle, so that made checking things easy. I could tap the cups back out with a minimum of fuss with a dowel and get my final hole work done with the sophisticated sandpaper-on-a-salvaged-disposable-paintbrush-handle method.

I pre-loaded the bearings/centering races by pressing the headtube hard on my leg, pressing a headset spacer into the centering ring on top, then tightened up a hose clamp on the steerer to lock it in place. I had no discernable play in the headset that way, so any wiggling I did to nudge the head tube into alignment was head tube, not steerer/headset.

Target head tube angle was 69 degrees, and I got that. Target plumbness for the HT was 0 degrees. I think I'm as close as I'll get there as well. Alignment tool from the headset cup on top shows bike within about half a mm of symmetry, good enough for me.



I couldn't resist putting the wheels on. It's starting to look like a bike!



I steered it across the basement and it felt super squirrely, more even than you'd expect from rolling on rims. Then I saw the fork was turned around 180, so I was shopping carting it. Turned it around and it actually felt like a bike too (with knuckle steering anyway. I have more experience with that than I would like, as I used to ride my trike to pick my kid up from school and I'd bring her bike and the only way I could steer it was by grasping the stem right at the head tube. Steering is a bit sensitive that way!)

Wheelbase is 1043mm now, I think, and I should have about 57mm of trail with 40mm tires on the bike. Head tube angle of 69 degrees, with some tiller, I'm hoping it'll handle well enough. Seems straight at least.

https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=570759&v=1Y

--SpiderMonkey

Edited by - SpiderMonkey on 02/24/2019 16:53:19
Go to Top of Page

warren
human power expert

USA
6470 Posts

Posted - 02/25/2019 :  21:26:23  Show Profile  Visit warren's Homepage  Reply with Quote
Cool, it almost looks like a bike!
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 03/02/2019 :  09:05:31  Show Profile  Reply with Quote
Finally did the front. A bit of a circus, since I don't know how many plies I need, and I was doing 2 things at once with this campaign (final bonding in the head tube as well as laying up the front bend). I think it went well.







Full description of my half-butted process here: https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=571106&v=1D

--SpiderMonkey
Go to Top of Page

carolina
human power supergeek

USA
1106 Posts

Posted - 03/02/2019 :  09:28:36  Show Profile  Visit carolina's Homepage  Reply with Quote
Looking good.

velosRus.com
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 03/04/2019 :  07:14:12  Show Profile  Reply with Quote
Decided to try a finding screw on the outside of the main tube as my alignment finder/twist insurance.







Need to trim and cover with a few layers of CF. Lower pinch assembly for this section is next up.

https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=571334&v=14


--SpiderMonkey
Go to Top of Page

Jeroen s
Starting Member

Netherlands
13 Posts

Posted - 03/04/2019 :  07:34:03  Show Profile  Reply with Quote
That is going nicely. I also read the long version on the other site. If u happen to get a bolt or screw accidentialy bonded in with epoxy i recently discovered a nice trick. Just put in the screwdriver or allen key that fits and heat that up, i used a very small torch that works on lighter gas. The kind of thing u use to caramelize in the kitchen. A soldering iron might also work. U just need to heat up the bolt to 60-70 degree celcius and the epoxy losses its grip. It takes just a minute to heat up enough.

This way u don't directly heat the carbon, and since the heat stays low there is little chance to damage things. I hold the torch with one hand and the screwdriver or long allen key with the other. That way i can feel it immidiatly when it gives away.
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 03/04/2019 :  08:48:32  Show Profile  Reply with Quote
Good tip. I haven't perma-bonded a screw into my projects accidentally yet, but there's always a chance.

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 03/23/2019 :  09:52:38  Show Profile  Reply with Quote
Big day for me. Validation (I think.) that the separable system works for this design. So, the pinch assembly for the main tube join is finished.





I cut a 90mm slot. I then mounted the fork and threw on the wheels and sat the kid on it. No tire flex or frame flex with her pixie butt 60 pounds. So I added another 100 pounds by putting myself on it. I could detect no flex other than what I could see from the tires. I bounced as well as I could. Stiff as a board. I hadn't even used carbon fiber assembly paste, nor torqued the pinch bolts very tight.



Looks like a bike that might actually be a bike before summer is over. Maybe even before it starts? That's sooner than I had planned. She's still got at least a year of fit in her LWB recycled recumbent.



Next step is putting together a DIY flipit stem/riser from the steering, which is already complete. I may actually redo the steering from a thinner-walled 28mm tube, because the 2-tube mast (adjustable for length) nests so tightly together that there's no room for any finish on the inner portion. If I use some 28x26mm instead of the 28x25, I'll have some leeway inside there, even after putting a sleeve inside with the inner-tube bladder trick to bond it into shape and take up some of the slack. But that's another bunch of work, so I'm not sure it matters enough to do. I can always put finish on the inner mast portion that's exposed, and a fabric sleeve over the rest (which would nicely gather the cables as well, just like on my Azub.) OK, that sounds like a better plan.

--SpiderMonkey
Go to Top of Page

Jerry
human power supergeek

USA
1475 Posts

Posted - 03/23/2019 :  20:26:53  Show Profile  Reply with Quote
Looks good! Your build is inspiring me to finish the carbon fiber work on my bike. Thanks for sharing.
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 03/24/2019 :  12:56:21  Show Profile  Reply with Quote
Thanks. I have never made a bike before, just little parts or fixing up the NoCom. As a result, every time something I do on this project actually works out, I am pretty happy. I am overbuilding, I'm sure, but I think the whole thing will still cut 5-7 pounds off her current ride, which is decent given that it's got those heavy disc brakes and disc brake wheels. There's another half to 3/4 pound excess in the separation system as well, and the extra bend adds some weight. I feel like I could make a straight stick bike out of this tubing with a couple of 622s or 559s that would weigh 19-20 pounds, without even having to buy anything exotic. This Chinese tubing seems to be really nice stuff.

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 04/13/2019 :  12:10:57  Show Profile  Reply with Quote
Slowly doing a little more work. The nice weather means bike commuting (along a new route that features lots of gravel, singletrack, and 6 or more creek crossings with trout, ducks, and stepping stones) and that means less time for building.

I made some right-angle CF stock to turn into T brackets for an overly-complex seat-bracket assembly I'm trying. I'll keep the old half-tube-cross 'n' hose clamps material in my back pocket for if this fails.





https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=574540&v=k

Also nearly done with the front pinch/clamp assembly for holding the boom. Once these are working, I can sit kid on bike and eyeball steering to make sure my measured and planned scheme there meets with reality. Then it'll be onto making the DIY flipit stem, and after that'll, it'll just be mounting the drivetrain and getting the details squared away.

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 04/28/2019 :  13:48:50  Show Profile  Reply with Quote
Got the front boom pinch assembly finished.









Frame weighs 1363g at this point. I'd estimated 1350g. Still needs idler mounting and a plate on the rear to cover the tube. Oh, and a derailleur mounting tube for the boom. A bit heavier than I wanted, but ya gotta build it strong when you don't know how strong to build it.

https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=576005&v=1O

--SpiderMonkey
Go to Top of Page

SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 05/21/2019 :  08:53:25  Show Profile  Reply with Quote
Finally got the seat bracket/clamp finished, or nearly so. I wanted to make a clamp that's similarly convenient to commercial clamps, that is, simple to loosen and move with just an 5mm hex key rather than loosening a bunch of clumsy hose clamps. (Those mounts are fine, but I wanted to see if I could do this, and from what I've weighed on my kitchen scale, there's not much, if any, weight penalty to this clamp. It did take longer to make, though.)








I have plans for a version 2 which will be lighter and simpler. I'll probably make version 2 right away and relegate this heavier one to my eventual bike.

https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=577939&v=2h

--SpiderMonkey
Go to Top of Page

Jerry
human power supergeek

USA
1475 Posts

Posted - 05/21/2019 :  11:09:00  Show Profile  Reply with Quote
Looks great! I have been following you here and on cgoab and it inspired me to finish some CF projects. I got one little project done and was getting ready about 2 weeks ago to do the large pieces. I need to do the large project outside and it has rained 10 of the last 14 days!

I really do like your new clamp. I am interested how it holds up, so I'll continue to follow any updates.
Go to Top of Page
Page: of 5 Previous Topic Topic Next Topic  
Previous Page | Next Page
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
www.recumbents.com © 2019 www.recumbents.com Go To Top Of Page
Snitz Forums 2000