Disc Brake tabs on Old Equipment?

[SILVERKINGPC]

Has anyone here put permanent/welded disc brake mounts on an old(pre/post war) frames or forks? Welded post-mount tabs?. If so, please post a picture.
No temporary bolt-on adapters or new Monarch springer linkages/seen em. Anyone out there in Ratland? I am attempting to do this on a project now, so I will post below. SKPC

 

[Bicycle808]

If you get bored, alot of guys on the Klunkers and Such Nonsense FB page have welded tabs to the treat, most often with a tube welded from seat- to chain-stay to stiffen it up a bit. The rear has the advantage of being triangulated...

I'm subbing to this thread because i'd like to see others' experiences, too

 

[SILVERKINGPC]

Cool B808. I don't do Face-Out,(book) and still not bored. Here is what I have come up with so far on my fork project:

 

[Bicycle808]

Welds look really nice right there

 

[SILVERKINGPC]

I can't weld at all much less doing it as well as that. I had to hand over some $$ . Both sides of the plate were welded for more strength.

 

[Bicycle808]

I thought you might have, although RRB does have some very skilled hobbyist welders on here, too... but those welds looked pretty ¨pro¨ from that picture. It looks like you got your money´s worth.

At this point, you´ve already got the fork modified for it; like I was saying in that other thread, these things don´t usually just snap and explode; they´re more likely to bend/warp slightly over time.

If i were you, I´d just ride it, but keep a close eye on the fork at first. If it holds up, just check alignment at regular intervals, but no need to obsess over it.

One good thing about disc brakes is, they require pretty tight clearances; any lateral bends will lead to rubbing, squeaking, chattering, etc. If any of that occurs, the fork would be one of the first things i´d check. (Of course, there´s a lot of other things that could cause the same symptoms.) If it bends longitudinally at all, your disc might not offer any signs, but keeping an eye on it would help. You also may find that your headset goes out of adjustment, depending on the situation.

But yeah, hopefully, I´m just being a nervous Nelly here, and in a while, you can just say to yourself, ¨man!! that 808 sure is a paranoid SOB... The 80s and 90s MTB forks that got disc mounts welded on, most of those were chromoly, but relatively thin-walled....which may be why they bent. Old cruiser forks tended to be much heavier gauge, but then again, they´re more likely to be high-ten or just mild steel, so who knws how they´ll fare? In the end, though, there´s a big difference between sustained downhill braking on trails, or the hot on/off hard braking one might experience in a MTB race, as compared to JRA on a cruise.

 

[SILVERKINGPC]

Exactly B808. Learn from my mistakes as I go through the process. I have not ridden this experiment yet, and plan to follow the advice of 808. These forks weren't built to run a disc brake, but this trussed design got me thinking. If it works or not, I will for sure inspect the alignments, bolts, and welds every ride at first.
Most old frames or forks couldn't take the forces because of lack of support near the caliper, and as B808 mentions, in the matl's & gauges. With old frames it may be easier as the stays were tougher. If anyone has pics of one, or has done it themselves, then post it up.
I am hoping for a performance boost to the Hawthorne, and if not, have to rethink it.
Below is the project bike Frame/fork idea taking shape in "Builds", 20's/30's Hawthorne(21st Century)

For those worried about the og frame, I am not putting disc tabs on it. Just the fork. I also have kept the orig. matching fork/truss rods for this frame so as to respect it's history..Preserve/protect 1st..

 

[SILVERKINGPC]

After doing the shim/washer dance, I have the disc running pretty much drag-free. The IS-to-Post mount adapter looks bulky to me. It still needs the housing shortened to fit. A cable-pull, post-mount caliper may be in the future.
Who knows if it'll rub when riding it, but I will soon find out.

 

[SILVERKINGPC]

I've been working on this slowly. When I would set the disc hub axle in the drops evenly w/quick release closed, I couldn't get the disc to line up with the caliper, and it was creating too much drag.
I found that when I put a clean wheel in the fork drops, the wheel sat twisted left when the fork was pointed straight. When I put a naked axle in the drops and compared it to the forks' pivot axle, you could see they did not line up. Either the Forks' left drop was pushed back 1/4", or the right drop was pushed forward 1/4". I just cold bent one of the arms back into alignment. Now the disc runs clean thru the caliper.

Here is a look at the brake setup on the bike with a diff wheelset on the bike to mock it up..

 

[SILVERKINGPC]

My hub finally got here!! I installed the disc brake caliper & lever, and have been running a temporary cheap disc wheel to get everything aligned. Incredible braking power! I had no idea how long it would take to get this figured out, and nearly abandoned the disc idea. Almost done....
When I get this wheel built and on the bike, I will post some finished photos.

 

[SILVERKINGPC]

Got it done! This idea was born when I began my latest bike build. Doubling or tripling the braking power of a coaster-brake-only bike intrigued me. I have not seen it done before on a prewar springer, so decided to give it a go. The truss rod/single pivot design of the Shelby Shock-ease fork is heavily trussed and proven tough, so it seemed possible. There are valid concerns about whether these old springer fork designs and/or materials can withstand the braking forces exerted by a disc brake caliper, but it didn't keep me from trying. This setup appears to direct the forces straight up into the fork crown.
I finally got everything set up running smoothly, and have put a bunch of miles on the bike. I am impressed by the large change in the bikes performance capabilities. With the additional braking power at the fingertips, the bike was transformed into something pretty special.
So far, I have not had a single problem with it, and am blown away by the stopping power gains. Rat-a-tat-tat!!!

Filed the axle ends flat for a secure press fit when bottomed in the fork drop. No room to move..