From: "tubus_nl, import en framebouw (marten gerritsen)"
Subject: Re: [Frame] fork rake
Dave Jenson wrote:
> This is Dave from Jenson Machine works.I am in the process of building a
> fork rakeing fixture and would like to know what math formula to use to
> calculate the length of the fork blade prior to bending to the desired
Make a drawing (sideview), figure out which part of the centerline has a
and [Degrees bend]/360 x 2 x Pi x Radius will give you an first
the straight lenght of the curved bit. Real lenght is probably slightly less as
the neutral bending line doesn't quite follow the centerline, but with short
bends this can usually be ignored.
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construction of the jigs has begun. i received full-size plots from my uncle this week. the plots i made by printing the BG101 Frame Plot chart to PDF, then opening the PDF in Illustrator and playing with it there. they're at least pretty close to accurate; probably within a mm.
cut 2x4s and plywood for Talbot's fork jig. bought 5/16" threaded rod, washers, wing nuts. now i'm missing the drill press i was using in classes. and i need a way to cut a hole for the fork crown--Talbot used the hole to braze in; i'm planning to pin and free braze, but i think i'll still need the hole to keep the crown from mucking with alignment.
cut 4 x 12" plywood for bending mandrel. bought EMT tubing for bending assistance, 3/8" pipe nipple and 1/4-20 threaded rod, nuts to hold the blade down while bending. this is all based on a drawing from H. James--email me if you want a scan. i made pdf scans of Talbot's plans for jigs as well.
i need sand to fill the blades with to prevent kinks. also i might switch to the S. Garro method of making two identical plywood pieces, then bevel sanding both so they'll form a valley when they're mated. he explains it better on frameforum.
also working on pine tubing blocks. bought 1" and 1.125" spade bits for boring. planning to enlarge holes with big files.
putting together an Enco order--files, rifflers, scriber, etc.
also working on cleaning up the various frame parts. discovering i need more and different files--smaller ones for the tight spaces. 80 grit emery is OK for larger curved sections, but i'll need needle files and rifflers for sure. i glued some emery to an old emery board, but haven't tried it yet.
sanded the main tubes with 400 grit to remove rust. coated with WD-40 to prevent it. gotta get something to remove it later--acetone?
i had wanted double-bent chainstays. Bringheli was out, so i got single-bent. putting the BB shell and stays together it looked like i'd end up with way too little tire clearance, so i'm returning them for straights i think. USPS screwed up so i have a day to think about it.
and i'm reconsidering the smaller front wheel idea.
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$50 Sugino XD300 165, 170, 175
$15 Tektro 221A levers
$14 Shimano HG-53 9-speed chain
$27 Nitto Randonneur bars 45 cm
$28/bike Tektro Oryx 1-pc pads
$62/bike Shimano R550
$44/bike Dia-Compe 750
$20 MKS platforms
$6 black leather toe straps
$13 Shimano Deore front hub M510 black/silver 32/36
$24 Shimano Deore rear hub M510 black/silver 32/36
$28 Sun CR-18 36
$33 Mavic MA-3 silver 32/36
$20 Kalloy Lapadre silver 27.2 x 350
$58 Brooks B-17 Standard black
$14 28.6 front derailer braze-on->clamp adapter
KONA STICKER SET
* 2X KONA DOWNTUBE STICKERS 300X30mm
* 2X KONA FORK STICKERS 180X20mm
* 2x HEADTUBE STICKERS 76X67mm
2x SEATUBE STICKERS 55X55mm
You are viewing a Pair of classic Raliegh factory bicycle frame decals, These stand out decals have a super strong adhesive, and give a strong superior look, on any raliegh. The lettering measures as follows; 1 3/16 high x 10" long. a must for restoring.Blooming purple filled white outer stencil.
THE SIZE OF THE TWO LARGER DECALS IS APPROX = 10" X 1.5" EACH
ANOTHER TWO DECALS SIZE APPROX = 7" X 1"
ALSO ONE LOGO DECAL SIZE APPROX = 2" X 2.75"
specs for mine:
DT (31.7 mm diameter) x 2 @
AUT 120 Introduction to Automotive Machine Shop
WEL 116 Welding I (Oxyacetylene)
EGR 115 Engineering Graphics
BUS 116 Entrepreneurship
File this dude under awesome.
Great little site, just a bunch of photos and text on his bikes and framebuilding tools. Wonderfully simple, casual prose. Badass homemade tools. I get the sense this guy would love Zen and the Art of Motorcycle Maintenance.
My favorites, and the reasons this link was mentioned on FrameForum.net, are the measuring tools made from telescoping radio antennae. He's also got a simple, cheap design for an angle measurer.
Above is a drawing screen captured from Martin Manning's BG 101 5.1 Excel program, with text added in Illustrator. Actually, I made some slight modifications to the text after measuring my frame parts (most of which arrived from Ceeway late last week), which aren't reflected in the drawing. The main difference is that the head tube is a bit longer, as the estimated crown height was a little too long. Also the dropouts I have are rather long horizontals, while the ones Martin measured must have been shorter.
My main concerns at this point are regarding steering. I'm worried that wheel flop may be a problem because of the combination of short 80 mm stem, 52 mm fork rake, and shallow 71.5° HT angle.
I'm working on a decal set, to be produced by CyclArt.
dammit i wish people would leave their names... i can't think of a reason why one wouldn't, and it would seem to be in the spirit that this whole blog was created to invite open discussion.
first, to clarify the stem thing. what i meant by "mid-length" stem was one in the middle of the range of lengths available. for the nitto technomic, that range in mm is 50-60-70-80-90-100-110-120 as i recall. thus an 80 (or 90) leaves the most room for error on either side.
sounds like i gotta check out this pneumatic trail thing.
the area that needs work now is the front end/steering geometry...i don't have the headset in hand yet, so i need to find out its exact lower stack height before locking anything down and building a jig.
the top tube is a compromise between fit and toe clearance. this is one area where i found an enormous amount of conflicting info. Paterek claims front center determines toe overlap--that 58cm is the magic number over which it's not a problem. R. Sachs says not to worry about it--that fit is infinitely more important. a recent discussion on the framebuilders list went on for a week.
i tried to strike a balance between the two Rivendell models i'm copying, the Atlantis and Ramboulliet, and my TT length is about mid-way between the TT lengths of their 58cm sizes. ditto for the chainstays, which are shorter than i had originally planned, but should make the bike a little more maneuverable.
i'm going with a 71.5° HT, a half degree shallower than planned, to allow for a short TT and decent toe clearance. this stretches things out on the front end a bit, so the chainstays got shorter to make up for it in handling. hopefully the wheel flop will be OK. i kept trail 58-59 cm with a 30 mm tire by increasing fork rake 2 mm. the front end is by coincidence very close to the cannondale touring model, which i'm planning to test-ride before building.
i'll attach a drawing soon; it's stuck on my home computer with no WWW access.
in cm unless noted
this was all done in BG 5.1 by Martin Manning, so the info below will be most applicable to users of that program.
sternal notch 148.0
arm length (avg) 65.75
femur (thigh) length (avg) 52.2
foot length (avg) 26.35
saddle height, BBc-saddle top 73.64
virtual ST 58.7
virtual TT 57.0
HT angle 71.5°
ST angle 72°
CS length 44.4
BB drop 7.75
fork rake 5.2
@ 700x30 tire
front center 60.93
BBc height 26.35
trail 59.3 mm
standover, mid-TT 82.18
TT angle to horizontal 2.5°
TT c-c 56.26
DT c-c 63.12
HT length c-c 16.23
front brake reach 64.0 mm (designed for cantis, long calipers or centerpulls possible)
HT upper free length 20 mm
HT lower free length 6 mm
fork length on steerer axis 38.75
seat tube Deda ZeroUno 28.6 mm
down tube Deda ZeroUno 31.7 mm
top tube Deda ZeroUno 28.6 mm
head tube Deda ZeroUno 31.7 mm
steering column TT Verus 25.4 x 240 mm
chainstays Deda ZeroTre 29.9 x 16 mm single bend
seat stays Deda ZeroUno 16 mm
fork blades TT Verus 27.6 x 20 x 400, 1.1-0.6 mm
seat lug Long Shen 74° long pt
top head lug Long Shen 74° long pt
bottom head lug Long Shen 60° long pt
BB shell Long Shen 60.3° x 62.3° x 7.3° x 30x1
fork crown R. Sachs/Long Shen Newvex
top eyes/seatstay caps Silva 16 mm
rear dropouts Tecnociclo 70° 2-eyelet
front dropouts Long Shen stainless 2-eyelet plug-in
chainhanger Columbine Quikchainger
brake and chainstay bridges 1/2" 4130 CrMo
bottle bosses stainless, dead-ended
rear rack mounts
cranks 175 mm 26-36-48t
cassette 9-speed 11-32t
rear hub spacing 135 mm, 2.5mm narrower if possible
steerer 25.4 mm threaded
stem 80 mm Nitto Technomic 26 mm
bars 45 cm Nitto Randonneur 25.4 mm
nitto shim 26.0->25.4 mm
i assumed a lower headset stack of 14 mm and an upper stack of 19 mm based on info in Paterek and specs on the Harris Cyclery site. this is until i can get a measurement of the actual headset to be used, likely a Ritchey Logic.
I decided to design for a mid-length stem, so in the event that I'm off on the TT length, I'll have a few cm leeway available in both directions.