Overload Tube?

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Coyote

Finally riding a big boys bike
At the risk of sounding like a noob,
what is the purpose of the overload tube on a 5 speed stick shift?
It must be something that couldn't be built into the shell of the shifter itself...
 

Oldbikeguy1960

Wore out three sets of tires already!
It allowed the shifter to move forward if impacted so that it lessened the chance of a groin injury.
No pretty way to say that.
 

WillWork4Parts

Finally riding a big boys bike
Not so much a moving forward issue, but a breaking the cable issue. If for some reason your 5spd stick shift derailleur binds while pulling it into low, the overload tube has a spring inside to allow for some give. The 3spd stick cable also had a much more visible spring to keep from breaking the indicator chain or from pulling/breaking the cable idler wheel.
 

Oldbikeguy1960

Wore out three sets of tires already!
I agree that would be a good reason to do this. Why only on stick shift Bikes? The lever operated derailleurs could conceivably be overloaded as well. There is no use of an overload tube I know of on anything but a few stick shift bikes.
When the shifter is pulled down to low gear the spring inside the tube compresses keeping some forward tension on the shifter. If the rider moved forward and hit the shifter, the forward spring tension would help move the shifter forward lessening the chance of injury. Below is a quote from Al Fritz, the father of the Stingray.
20220124_145034.jpg


The Schwinn Stik Shift was designed to give. What else on the shifter would allow that to happen except spring tension in the overload tube? That is the basis of my answer about the shifter giving on impact.
If anyone else has another theory on how the shifter was designed to move under impact, share it please.
Rob
 

WillWork4Parts

Finally riding a big boys bike
Think about how a Schwinn derailleur works, without a cable installed the derailleur arms are spring loaded to a default of high gear. With cable hooked up, the way it actuates, moving the shift lever aft will pull on the cable, pull the arms, overcoming the derailleur spring and pull the chain towards low gear. The force it takes to compress the overload tube spring is just greater than what it takes to compress the derailleur spring for this to work. The friction washers of the shifter hold it in position until you move the shift lever forward. Pushing forward on the lever only relieves tension on the cable. A stranded cable doesn't push anything effectively without bird-caging and causing damage to the cable. It's the derailleur spring that moves the arms and chain back into high gear, not the shift lever or cable. (Start talking about a Positron solid cable setup and everything changes though!) With that being said, the only things effectively keeping the top of the shifter from pushing forward are the lever's friction washers and the forward(high) shifter base stop. Those 2 things are not affected by the overload tube. I think the statement made about "give" would either have to be PR smoke or about the lever offset change in 69(same year razor edge fenders went away). If the lever is offset to one side, it's also probably more likely to slip at the bar clamp, side to side...instead of the rider's force coming down straight in line with the shifter angle(fore/aft)and dead center left to right with a perfectly straight piece of steel between your legs(think of the instance of a pole vault athlete skewering themselves). Compare that to a bent offset lever changing the downward force of the rider into a sideways(slipping on the top tube) lever action. Either way, in 1973 it still didn't have enough give to be considered safe, still operated under the same principles as Shimano, Suntour, and Bendix....and ended up outlawed. Coming down on the shifter with an aft motion though...that is where the overload tube comes into play protecting the cable. With the force of even a 60lb kid on a fulcrum with that kind of ratio(8" on top part of the lever and maybe one inch on the cable side of the pivot), if the chain can't move out of the way fast enough with the derailleur, that little bitty cable doesn't stand a chance. Under under that tension it will snap at the end fitting or slip through the eyelet on the derailleur. .... ...unless there's a spring set in line with the cable, aka overload tube. That cable isn't strong enough in either direction to hold under that weight, not even slowly being lowered onto it. It's the lever itself causing the injury, especially when forced onto either shifter base stops.
I think the reason Downtube shifters don't get overload springs is partly because they're shorter, but mostly because they don't have riders accidentally falling directly on them.

Keep in mind the way earlier top tube mounted shifter, the New Departure DD Two Speed. These also had overload springs built in line with the cable.
IMG_20220124_1914348.jpg
 

Oldbikeguy1960

Wore out three sets of tires already!
I do understand the derailleur principle. That was an excellent explanation though.
Part of my reasoning agrees with your explanation. Pushing forward on the lever relieves the tension, not only on the cable but on the lever as well allowing the lever to move forward. So in effect it would also act as a way to get the lever out of the way.
In that situation the movement of the derailleur is not as important as the movement of the rider and the shift lever.

About the Consumer Product Safety Commission.
That fiasco started with Ralph Nader and his Unsafe At Any Speed rant. For thousands of years boys have played dangerous games, done dangerous stunts and altogether lived dangerous lives.

Do you remember a game called Mumbltypeg? Throwing a pocket knife to see how close you can get it to the other players foot is probably not as safe as playing World of Warfare, but it got kids out of the house and in the fresh air doing something. We played Army, sometimes with BB guns climbing on and jumping off garage roofs and out of trees. Yet somehow I lived thru all that without any help from the CPSC.

I owned and built stick shift bikes when they were still new, and I rode them like I stole them. I once jumped a six foot dirt mound at full speed in fifth gear. Everything was cool until I flipped over and landed about 30 feet from the hill, right at the edge of the street with the bike on top of me. I got up bleeding from the scrapes on my arms and back. Not counting the nose bleed from the bike landing on me. My bike was fine, it had something soft to land on. So I rode it around the block, back to the construction site and jumped the hill again. That time I landed the way I was supposed to. Boys all over America were probably doing the same thing and some of them were getting hurt.. What was the CPSC going to do about that? Outlaw dirt hills? Or bicycles altogether?

We live in a nanny state and it all started with the CPSC. The day the Stik Shift disappeared from bicycles was the day the Stingray and a lot of other bikes died. But it didn't stop boys from doing dangerous things. Skateboarding and BMX were no more safe than what I did on my Stik Shift Stingray.

That was almost 50 years ago. By now the CPSC has outlawed everything that they could possibly perceive as dangerous.
Some places you cannot buy spray paint or model cement unless you are 18 or older. When I was 14 I probably bought a can or more of spray paint a day to fix up an old bike I picked up off the curb. Imagine what a pain in the @$$ it would've been to get my parents to go to KMart or Sears and buy me spray paint every day. We only had one car and my dad worked 2 jobs. The only time my mom had the car was a couple hours in the mid morning, he would get home around 8:30-9:00am and have to be at the other job by 2:00pm. I was in school that whole time so I would've been out of luck if the CPSC would've accomplished what they have done now 50 years ago. I hate the CPSC and everything they stand for. It isn't about safety. It is about power and control.

I could rant on this for hours, but I have other more fun things to do. It is hard to clean bike parts when you are typing on a forum. I do not know your age man, but I am 62 years old. The clock is ticking for me and I do not know how many times I am going to get to wind it up again before it quits working.

Hey man, like I said earlier your explanation of how a derailleur works was excellent and I could not have done better. Maybe my belief that it also helps the shifter move forward in an accident situation is a secondary benefit but the benefit is still there. I am fairly certain they only use that overload tube on some Stick Shifters, Schwinn and Shimano are the ones I know of from my era. There are no overload tubes on any other type of shifter, so there must be other ways to accomplish the function that the overload tube does. Why didn't they use one of those methods?

I appreciate the work you did to type out that explanation, as I am sure others also do. The debate was cool for me and I hope it was for you as well man.
Thanks, Rob
 

WillWork4Parts

Finally riding a big boys bike
Hey man, I'm with you on the cool factor that the Stik Shift brings...and I don't know of any safety factors that were attempted to make the Stick part safe. You could make it break away if you really wanted...but that takes away from the look and the durability that made Schwinns appealing at that time(and still today). I think people realised that then, that there wasn't a compromise, it was just easier to move on to "new" handlebar mounted controls. I know Road Riders that still today raise crap about how unsafe downtube shifters were...
I still use all of the above. Under the right control, I don't see the a problem with these parts on bikes. I do see how their use has happened to cause injuries...but I know the attention it takes to avoid that. I just take the "safety items" as people trying to keep their kids safe when there's no one there giving them the hawk-eye.
 
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