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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 05/21/2019 :  11:30:30  Show Profile  Reply with Quote
I'm glad to have this mostly finished, as I have been hesitant to begin finalizing the steering boom design and DIY flipit until I get the kid onto the bike so I can see how things shake out. Most of my designs have been close enough to right that the adjustability I'm building in for growth more than cover anything I missed, but I would still rather measure a few more times.

Next step here is, I think, bonding the brackets onto the seat, then sewing up a seat cover, and sitting her on the bike. I'll have to be the seat stays for that, since those won't go on until later.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/01/2019 :  08:04:20  Show Profile  Reply with Quote
I improved my seat bracket/clamp to remove the potential for slop, flexing, fatigue. Getting a threaded interior tube properly lined up for threaded nuts on the inside ends of same tube took me a while to conceptualize, but I finally got it.







https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=579265&v=g

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/01/2019 :  13:40:41  Show Profile  Reply with Quote
Aaaand, I got the brackets tacked onto the bottom of the seat and filled in with carbon fiber fabric.



https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=579303&v=1G


--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/01/2019 :  19:30:49  Show Profile  Reply with Quote
They almost look too nice to wrap with cloth.






--SpiderMonkey
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warren
human power expert

USA
6470 Posts

Posted - 06/02/2019 :  08:33:24  Show Profile  Visit warren's Homepage  Reply with Quote
Heavy duty!
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/02/2019 :  08:55:25  Show Profile  Reply with Quote
First timer/ignorance build = 350 pound weight limit for 65-pound kid.

I have to live with watching her ride it, so it's good for my sanity to have it overbuilt.



--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/08/2019 :  10:28:56  Show Profile  Reply with Quote
Whatcha think?

I put some duck tape on the seat frame, a pad on the tape, masking taped some seat stays (let the record show this is a bad idea) and mocked up the bike today.



I put the kid on, and I see already the seat needs to go back a bit, which is good, because that'll put the weight further back and maybe give me a nice spot toward the middle to put the idler so further seat / leg length adjustments won't get any idler interference with the clamp.



My goal was that this bike would also fit her as an adult, a wife-sized adult, so I put the wife on the bike. (adjusted the seat itself to its longer length, moved the seat back, pulled out the boom). At her X-seam, it appears to fit. It's actually adjusted a little past her X-seam here, I think.



Seat and pedal height work out to close to what I thought in the design. Seat is about 505mm from the ground, BB center about 610mm from the ground, for a 105mm or 4 inch difference. That differential is almost the same as our Azub mini's seat-bb differential, and we find those very comfortable. It's also enough to let you get a decently aerodynamic profile, IMO, at least for a touring-oriented suitcase bike. (It will look like an upright brick to some of you!)

Wheelbase is 104cm. 69 degree head tube angle, so about 57mm of trail. Tiller will vary with rider preference as handlebars will be adjustable for angle and length. I can start working on that, then fabricate a DIY flipit. I'm thinking of making it sort of like the one from performer, which has the hinge sides straight upright along the sides of the stem. That'll be much easier to fabricate and attach strongly (just wrap!). Might require an incorporated cap rather than a separate piece. I think I'm going to go about 40mm height for the stem tube itself, then the uprights as tall as necessary, single M6 pinch bolt since I don't feel like I can easily pack 2 of my usual assemblies in that 40mm (or I suppose I could go 50mm).

Anyway, seems like it will actually work as a bike.

As for whether it would work for me with just a longer boom, I couldn't figure out today. I sat on it, ripped the masking tape stays off, nearly knocked it over, and decided to figure that out later.

--SpiderMonkey

Edited by - SpiderMonkey on 06/08/2019 10:39:16
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warren
human power expert

USA
6470 Posts

Posted - 06/09/2019 :  07:54:56  Show Profile  Visit warren's Homepage  Reply with Quote
Looks good, it should be a fun little bike. Hi Jen!
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/10/2019 :  18:34:14  Show Profile  Reply with Quote
I had originally planned to my flipit stem by hacking apart a Chinese carbon-fiber road stem, but when I got that stem, it seemed too nice to cut up.

I then thought I'd just use some cheap Chinese carbon fiber headset spacers, say, 50mm tall ones, as the base, and build on top of those. Alas, when they showed up, they weren't so carbon fiber. They had a very thin skin of carbon fiber on the outside, and the inside was all fiberglass. I suppose that's OK for a cheap spacer, but I wanted better for the basis of the thing that keeps the bike from veering into oncoming traffic. I wouldn't want to startle anyway away from their Facebook with a pesky bicycle crash.

So, I just decided to make some carbon fiber tube with the exact inner diameter of steerer tube (28.6 mm). I cut some of the steerer off one of the forks, and I slotted it along its length, then put a piece of tape over it, followed by a layer of a discarded plastic bread bag. The bread bag somehow stuck inside so I couldn't just squeeze the mandrel down and pop the thing loose. Lots of whacking with a convenient length of PVC and a plastic tent-stake mallet did the trick, while providing me with the exciting opportunity for a trip to urgent care, if I didn't not exercise enough care with the hammering.

Came out as lumpy as all my other attempts at wrapping tube with electrical tape, but this was solved, as usual, by my obscene tube-in-tube wet-sanding in the utility sink. Now I've got enough tube for 3 nice, snug-fitting, 45mm, 15g base bits for DIY flipits.

Wall's about 2.25 - 2.5mm depending. Dang thing feels rugged. A fellow could get used to this carbon fiber stuff.







--SpiderMonkey

Edited by - SpiderMonkey on 06/10/2019 18:35:38
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/19/2019 :  15:06:14  Show Profile  Reply with Quote
Putting parts on seems exciting, but then you start to wonder if you're an idiot or not.



Looks like the chain line will be pretty clean and have a gentle deflection right behind the separation in the frame.

Kid will definitely have some heel interference to get used to. Looks like with the current tire (a 42mm Marathon Supreme, perhaps the last ones for sale anywhere...) there's about 1cm of clearance with the cranks with the boom in all the way. She may need it out a bit when she first gets on.



--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/23/2019 :  21:32:15  Show Profile  Reply with Quote
Got the idler mounting tube tacked + filled. Needs a few layers of tow and fabric to strengthen it up, but seems on track.

https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=582129&v=1h

I decided to make a little jig for mounting these transverse tubes nice and square. (Have to do 2 more bikes + 2 more seat mounts requiring same.)



2x washers turns out to be exactly the same thickness as the right angle stock, so using them means the end of the idler tube is flush with the side of the main tube.



With idler tube on the little jig and bike on the main jig, I just had to zero the angle finder to the jig and then tape the little idler jig to the main tube when I got it flat. I don't normally get this closer than a couple tens of a degree, but today, victory.



Did some carbon wrapping to fill it mostly in and compressed. Epoxy cures quickly in the summertime garage, especially after you park a hot car in there.



Tested the prospective idler. Looks like it'll fit pretty well after a washer and the plastic from the idler chain keeper are sandwiched between the idler and the tube.







--SpiderMonkey

Edited by - SpiderMonkey on 06/23/2019 21:36:46
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warren
human power expert

USA
6470 Posts

Posted - 06/25/2019 :  08:27:27  Show Profile  Visit warren's Homepage  Reply with Quote
It's looking very good. What are you going to use to keep the chain from popping off of that idler?
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/25/2019 :  11:46:26  Show Profile  Reply with Quote
Scrap thick HDPE from protein power cans, I think.

I can either make a couple discs to run along the sides and do an L-shaped keeper as with most designs.

First, I'll try a variation on what I did with the return idler for her current bike, which was just to wrap a strap of that same plastic up and around. Like this, but with the keeper on the bottom since that's where the chain will be. I may have to heat and bend the profile a little to flare it so it responds well to backpedaling.

I never did care for the rattly lower idler keepers on the bikes I've got and ridden (either clunky metal plate or clunky aluminum tube) so maybe a smoother, wider-radious piece of plastic will be an improvement.



I suppose it may not work, even though the above return idler is silent and absolutely carefree. Of course, little tension there, and the chain's up top, but even on gravel, I've never noticed a single chainflap or rub.

If version 1 fails, I'll tinker, and of course if I have to I can always pay up for the real thing.

Biggest PITA right now is that no hardware stores around here have long M8s, so I'll probably have to buy a lifetime supply from McMaster to get them.

--SpiderMonkey
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Garrie L Hill
human power supergeek

USA
1809 Posts

Posted - 06/25/2019 :  15:49:08  Show Profile  Reply with Quote
What length, grade, thread M8 do you need? Iíve gobloons of them and would be happy to slip a few in UPS and send them to you.

Garrie "carbon based lifeform" Hill
HPRA Co-Dictator of the East
for pics of some of my time and money sucking projects
http://s58.photobucket.com/albums/g277/cfbb/
and videos
http://vimeo.com/5513519


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Garrie L Hill
human power supergeek

USA
1809 Posts

Posted - 06/25/2019 :  15:51:30  Show Profile  Reply with Quote
Gobloons = a technical term equal to 1k times one dozen scads.

Garrie "carbon based lifeform" Hill
HPRA Co-Dictator of the East
for pics of some of my time and money sucking projects
http://s58.photobucket.com/albums/g277/cfbb/
and videos
http://vimeo.com/5513519


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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/25/2019 :  20:30:45  Show Profile  Reply with Quote
That's generous Garrie. (Maybe I should save my real Garrie favor for if I decide to cut open my NoCom to bond in a new head tube to make the damn bike straight, since I don't think I can pull off a hiddenset CF fab.)

I'll figure the length in a couple days. I may take a few mm off the left side idler tube to keep the nut tucked in under the main tube rather than sticking out past the side, and final length I need to check with chainline and eventual idler width. Since I'm not sure how my keeper system will work (or if I need to punt and order an idler from T-cycle) it'll be a few days.

None of us are Hulkish in the house, so I was planning on 18-8 stainless, 1.25 thread. Pretty sure that's what's on the stickbikes and nocoms. (never noticed any rust, but never stuck a magnet on 'em to check.)

I was wrong about the lifetime quantity I guess. (That's my M6 and M5 supply now!) McMaster sells the longer M8s in reasonable 5 and 10 counts!

--SpiderMonkey
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strayray
Warren

USA
13 Posts

Posted - 06/27/2019 :  05:23:58  Show Profile  Reply with Quote
BoltDepot will sell down to the single bolt.
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/27/2019 :  18:29:40  Show Profile  Reply with Quote
Thanks, I'll check them.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 06/27/2019 :  18:32:37  Show Profile  Reply with Quote
After a few campaigns of fill, fabric, trim and repeat, I've got the idler axle tube mounted. I think it's beefy enough for my kid, or even my scrawny legs.









Of course, if it's not, it's just grind and try again. It's nice to have an eraser for these builds.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 07/05/2019 :  13:25:36  Show Profile  Reply with Quote
Got the front DR post mounted in good order.





https://www.crazyguyonabike.com/doc/page/?o=1mr&page_id=583510&v=1Z

Only problem left up front is that the twist shifters I got are wide index only on the left side. Since they're mountain pull and it's a road derailleur, the indexing doesn't match well and there's rubbing in the center ring. I didn't expect this as every other left side twister I've ever had has had "micro" indexing that lets you trim it to where it's necessary, like friction, but with little steps.

Solution I guess 1) buy friction shifter for that side. 2) buy other cheap twister with micro-indexing 3) monkey island this thing by cutting an indexing notch inside for the indexing spring at the right spot. I sort of like option 3.

--SpiderMonkey
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alevand
human power expert

USA
3541 Posts

Posted - 07/05/2019 :  21:06:42  Show Profile  Visit alevand's Homepage  Reply with Quote
I don't like grip shifters, I cant down shift then when my hands are sweaty.

C:
Tony Levand

Edited by - alevand on 07/05/2019 21:07:25
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 07/06/2019 :  08:56:06  Show Profile  Reply with Quote
That depends on the model. I never have problems with the SRAM until I got them super worn out. The microshift ones have even better grip. The Rohloff one is super slippery when wet. Wrapping it with a couple rubber bands fixes the problem, though. Less of a problem if you're wearing gloves, and I usually am since they're nice in a tipover.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 07/06/2019 :  10:03:00  Show Profile  Reply with Quote
Since I was beyond the return window on a couple of sets of the cheap microshift shifters, I went ahead and tried to re-index one of the left side twisters.

They're really simple and super light (120g for the pair), so I was hoping to get some mileage out of them. Also, I figured Warren wouldn't have let something like a little indexing problem stop him from mounting something already in the parts bin!



The interior is a very simple ratchet. The twister pulls right off very easily. You can see there is only one index notch between the ends of the indexing area. Gear 1 is where this is currently set. Gear 3 is clockwise, about the 3 o'clock slot. Two is at the 1:30 mark.



Both 2 and 3 were a little too much pull since shimano-spec mountain front DR pull (this spec) is a little more than shimano road-pull front DR pull.

I just jigged the twister up in my drill press and carefully went at it with a 2.5mm drill bit. This wasn't enough to get the notch fully shaped, but it was a good start. I finished them (getting the proper depth, or the spring would skip right over them) with a small Dremel cutting bit.



In about 10 minutes I had a new 2nd index notch and a new 3rd, each a bit sooner than the prior ones. In that photo, I'm in the earlier gear 2 notch. I had to eyeball it, and I also didn't want to get too close to the first notch and merge the two into a large and useless indexing spot. I think I'll be able to get things set properly this way. If not, I can always fill and try again.

Of course afterwards I re-greased the thing with blue part grease and it got inside the indicator, making it really ugly. I pushed some isopropyl in and took the window off to wipe it, and the grease came right off, but so did the number 1 indicator. Talk about a comedy of errors. I put a new one on with a sharpie and closed it up.





--SpiderMonkey

Edited by - SpiderMonkey on 07/06/2019 10:03:38
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strayray
Warren

USA
13 Posts

Posted - 07/07/2019 :  06:54:28  Show Profile  Reply with Quote
Shift indicators are overrated.
I had Shimano twist grip shifters that were difficult to shift with sweaty hands. I can't blame the shifters, because they were designed for the grip angle of a mountain bike handle bar and probably work fine there. After trashing a wrist in a snowboard accident, it was impossible to shift, so I went to lever shifters. For my handlebars, that meant mounting the shifter upside down to crowd it into place. That puts the shift indicator out of sight, but I haven't missed it.

It also made for an interesting first week training to the swapped lever positions!
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warren
human power expert

USA
6470 Posts

Posted - 07/07/2019 :  08:34:15  Show Profile  Visit warren's Homepage  Reply with Quote
Nice!
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