The Golden Boy 

I'm glad you weren't hurt!

As gugie says:

Doug Fattic 

All these fork blades you mentioned have been used by my framebuilding class students. You do NOT want to try and smush the Toei Special blades into a Pacenti MTB crown! That is a recipe for disaster! First of all that crown is very difficult to braze with perfectly fitting fork blades. When a student has chosen these blades I have always had to finish doing the brazing. They are also very challenging to blacksmith them so they have full contact around the blade making brazing easier (so the silver doesn't run away and create gaps). What makes the Toei Special blades special is that the small end has a constant diameter for some distance over the last couple of inches. As a result they are easier to bend and be more flexible when riding.

The problem with some fork blades is that when they are swaged down to make the taper, the small end gets really thick and doesn't like to bend. That puts material where it isn't needed which results in a harsh ride. The old Nova blades are an example. For years I've had students use True Temper blades which were great but they stopped making them.

The pre-raked forks from Framebuilder's Supply were nice from the one example I've seen in class. That is the fork blades to use with the Pacenti MTB crown. If you are not a really good brazier (and I mean really good not ok good), I would chose the full slopping fork crown in the picture I'll attach.

The Kaisai Continental fork blade are a decent fork blade but a bit on the heavy side at over 200 grams. I wouldn't use them for a low trail fork. Even though the small end is not thick from swaging, they start to taper larger right away so they are best used for forks with standard rake. This last Friday we raked a couple of pairs in class. I'll braze an example right before a student so they can see how it is done (this is after a lengthy explanation). Even though both were raked to 50mm, the one was bent on a 6" radius block and the other on a 10" so he could tell if where the rake was placed made any difference. We also placed the rake on a different part of the blade (a builder can choose what part of each end to cut off).

If you are doing a low trail fork using cantilevers , the right choice is the Kaisai Imperial (like the old Reynolds shape) fork blades combined with the Rene Here fork crown with 52mm of clearance between blades. The greater oval shape of the Imperial blades provides more front to back resistance to braking forces. Don't even think about trying to make those blades fit a Pacenti MTB crown.

This is the fork crown that is easiest to braze if using those pre-bent low trail blades.

seypat

I looked. Serial # is 038102. 1982 model year. Cable stop is on top of the chainstay.

AJI125 

I've got a 1982 613 (531 DB main triangle, Ishiwata Magny 10 stays and fork blades). No inner tangs. Interesting data point, I was soaking tubes in Evaporust due to bad top tube rust and a few spots along the frame (all consistent with a heavy sweater). When I was done I also figured I'd soak the fork, since I knew some of the history of these forks and also that there was some rust (superficial or not) around the cracks typically.

1) The fork blades (Ishiwata Magny 10) had a tremendous amount of black material come out after Evaporust soak
2) The frame stays (Ishiwata Magny 10) had a tremendous amount of black material come out after Evaporust soak

My understanding is the black material from Evaporust soaking is dirt/debris and/or the chelated iron (I could be getting this wrong but I believe Evaporust is a chelator Edit: looked this up and it's probably the carbon from the steel and/or ferric sulfate that it converts the ferric oxide to). For once all those years of Chemistry for ChE helps. Is there some possibility the Ishiwata materials were stored/finished/uncoated improperly where they were more prone to rusting? Exterior of all these surfaces, sans the 531 main triangle from sweat I believe, was/is in great condition.

Also I believe my steerer was a Tange also. I briefly used a Tange CrMo aftermarket fork from around the 90s while I played around with configuration and waiting for a shorter stack headset. Ride wasn't quite as good as the stock fork, I feel comfortable declaring.

scarlson 

I do remember you saying the fork was suspect, and recommending I reuse the one from my cracked frame! I'm quite happy I got to mess with this fork because it was good training.

seypat

This is why I read bike forums! Thank you very much for the info and explanations. I bet that's a great framebuilding class.

pcb 

Just want to give a tip-o-the-hat to Insidious C for offering a full refund on an item he warned scarlson might fail. Also a chapeau to scarlson for saying he knew the job was dangerous when he took it.

Lotta a-holes out there, so I like to celebrate niceness.

scarlson 

It's true - but there is a little bit of a joke in here that you may not be privy to. Insidious C. gave me the frame and fork for free!

pcb 

Free? Freeee? Refund? Reeefund?

Well, then, don't you deserve some cas$h anyway for your pain and suffering, or at least for your inconvenience?

scarlson 

Thanks for the explanation! I know the full sloping fork crown you're talking about. I believe it's about 60mm inside. 60mm inside should be sufficient for 48s and fenders, so that seems like a good option. I think the René Herse fork crown is too narrow for 48s and fenders, unfortunately, otherwise I'd go that route. There is always the option of making my own twin plate crown on the milling machine, but I don't really want to. Do you know if those pre-raked blades have really thick walls at the bottom end as well? Or are they thinner like the Kaisei blades?

Doug Fattic 

What I remember is that the fork blade thickness was well balanced. The small end diameter was a bit larger than the Kaisai. Really it is your best option that I currently know about. I would certainly use them on a low trail frame if I was making one for myself.

sd5782 

I also just purchased 3 bikes in a lot for cheap as a group. One indeed was an 82 Trek 412. I figure I have maybe $30 invested in it. The beautiful Suntour VXgt that I took off of it was worth what I paid. Here in the Midwest we only get real bad rust if something sits out in the elements. This bike had no rust and the fork looks great.

I am going to build it up as it is in my size and I want to experience the Isiwata 022 tubing, especially as to how it compares to my 83 Trek 700 with full 531. First attempt was a disappointing ride that I attribute to the awful Armadillo protected tires on it. On this one, I am not afraid to ride it, although I am old and slow. Selling it would call up some ethical questions. No monetary loss, but interesting research on this one.

bikemig 

I have one of these as well but I paid a bit more than you did at $50. There were clearly more than $50 worth of parts on the bike. I wouldn't sell it. I can use the headset so I think I'll pull the fork and HS and donate the frame to the bike co op. It's a good frame. I'll hang the fork in my workshop as wall art.

I have a full Ishiwata Trek, a 1979 Trek 510, and it is a fine riding bike.

sd5782 

Wow, $50. As you said parts are worth more. I wouldn’t think in Iowa you have rust problems either. As you said though, parting with the bike/frame will require disclosure or parting out etc. Perhaps a suitable donor fork may show up somewhere if someone knows what to look for. As you and I have higher level Treks from the same era, it is probably not a real urgent project. Nice looking bikes though.

scarlson 

Ha, did not see this activity on my ol' thread. But I have something to contribute, too!

I built most of a fork jig but have to take a break from it because now I've been forced to travel for my PhD work. I took my Vitus with me, because I managed to get a hard travel case from a friend. I had wanted to do a lightning-fast fork build and take the Trek, but it didn't work out, timing wise. A forum member offered me a Trek fork at a very reasonable price, as well, but I couldn't get my act together before my travel date to get the fork and put everything together, including brazing on brake posts. Would be cutting it toooo close.

My next idea was to take a fork from a Schwinn World Sport I have in my basement. Imagine my surprise when I found out that appears to use the SAME Ishiwata fork crown! I wonder if anyone riding those has experienced failures. The dropouts were different (Schwinn safety dropouts with the hole for wheel retention washers), so maybe the blades are different too. I dunno. The steerer was too short anyway, so I had to scrub that plan.

Anyway, fork jig coming soon!! I'm building it off Alex Wetmore's general design. Looks good to me and I have all sorts of small pieces of 8020 lying around.

repechage

go twin plate crown then. Put the flex in that.

I forgot, did not Trek recall these Ishiwata forks?

scarlson 

I don't think Trek recalled any fork during their C&V era, at least not that's reported on the vintage Trek website, but I could be wrong. Of course, Lambert/Viscount recalled their death fork, but that was a bigger deal, I feel like. I believe one C&V Bikeforum-er spent some time in a coma because of one. All the Trek death fork does is make the rider feel drunk! Should it be called the drunk fork? They do make a lot of beer in Wisconsin.

As for a twin plate crown, I've toyed with the idea. I'd like to do a sloping one, like came with my old Colin Laing tandem, but I think it would be a lot of work. Then I could make it whatever shape I want, and be able to use the Kaisei blades!! But seriously it would be prudent to try to make my first fork build a simple one, so I'll likely stick with the pre-raked blades and sloping crown. Maybe I'll think about CNC programming for the Imperial Oval. I wonder if the CNC mill can easily do that without requiring me to do a lot of *thinking*...

repechage

Masi built forks with straight blades then formed the curve all at once on a bending fixture that caught the dropouts
Very cool to watch actually

confente did the same
I’m sure there were others.

there is a video of one of the Japanese builders making a fork- a bit fussy I think but it works for him. May have been Nagasawa

plonz 

Scary pics. Glad you escaped without injury Sam!

scarlson 

Indeed! I think (and @southpawboston suggested) the failure would have been more gradual with sidepulls than with the cantis I had on there. But the VO minirack held things together pretty well. Perhaps without the rack, the fork would've broken off. But also, without the rack, I may have noticed it sooner, while the cracks were less far-along.

I've re-raked forks like that. I prefer a jig that cradles the blade just adjacent to the dropout though, because sometimes a less-than-perfectly brazed dropout can be pulled right out! I've seen it - it's real.

bulgie 

In about '72 I was working in a shop that sold Raleighs. I was assembling a brand new Grand Prix (second model up from the bottom in the "10 speed" category) and one fork dropout didn't look right. With the wheel out, I rapped lightly on the fender eyelet with whatever wrench was in my hand (not a sledge hammer!) and the dropout fell on the floor. It had been held in by rust — zero brazing, not even a tack.

The boss threatened to dock my pay for it! Like it was my fault? But the other employees stuck up for me, and he backed down. He really was mad at me though!

Mark B

repechage

When chrome plating is a structural material.

nlerner

I had that happen with a Raleigh SuperCourse MkII. It had a stuck stem, so I clamped the stem into my vise, installed the front wheel, and figured I'd use the leverage of the wheel to try and rotate the fork. Right side dropout popped right off the blade. Didn't look like it had much brazing material on it at all:



Remarkable that it held for about 40 years.

bulgie 

That's whay they call them drop outs.
<rimshot>

repechage

Bench failure is much preferred to in-use. If it could not survive re-raking, then is did not deserve to be used.
We live in so much danger.