Concept hooded rocker dropout design

[tigoat]

I have been a big fan of the hooded dropout design (Breezer or Wright?) but recently have also impressed with the rocker type due to the ingenious locking system, so I thought I would try to conceptualize a new design that combine both elements. Attached are some cartoons of my concept for your review. To my surprise, I was able to get the rocker arcs down to a very compact size, even slightly smaller than the slider type from Paragon. In fact, it can be machined from a 2.25" x 2.25" block. Not sure if it can get any smaller than this. As it swing through those arcs, it has a vertical variation of less than 0.02" (very insignificant) and a horizontal travel range of around 0.80", which should be comparable with those sliders from Paragon. If this design is proven to work then hopefully we can convince Mark to make some. What do you think?

[EnginCycles]

Mark will have the new Toggle Drop ready this winter. It is what you are asking for. The biggest issue IMO and why I wanted the Rocker made is the lack of a low mount on the brake.

[Will Neide]

A hooded rocker dropout with low mount disc tab would be perfect. (and reasonably priced)

[afwalker]

^^Drew,
I know paragon is modifying the toggle drop, are you saying there will be a low mount option too, not just the post mount shown in the video?
cheers
andy walker

[adarn]

Why all the holes?

I've only built one frame with rockers, but I was surprised by how much they mess with the BB height. I'm excited to get my hands on a pair of the toggle drops.

[EnginCycles]

Why all the holes?

I've only built one frame with rockers, but I was surprised by how much they mess with the BB height. I'm excited to get my hands on a pair of the toggle drops.

I have built more bikes with the Rockers than most if not all. The BB drop movement is undetectable if the drop out is positioned correctly.

The toggle drop will not be a low mount drop out as far as I know. Just a more production like version of the one he made for his belt drive bike. I am also not sure if it is going to be done in 17-4. Definitely titanium first and probably later in 17-4.

[tigoat]

Thanks Drew for the link to the video. It is very interesting design and is indeed along what I had in mind. However, it looks pretty complex with the mechanism but I hope it will work out great. I like your two bolts and one pin design better, much simpler. Your dropouts look very cool but the only issue I see with a plate style system is that they can be very flexy. I am a fan of the hooded design not just for looks but for the strength. I have done a few finite element simulations on various types of dropout design to come to this conclusion. I will see if I can dig up some of my analysis data to post here when I am at work.

[tigoat]

A hooded rocker dropout with low mount disc tab would be perfect. (and reasonably priced)

Didn't think of it but I will see if I can flip the post mount down and under the seat stays in my concept model.

[tigoat]

Why all the holes?

I've only built one frame with rockers, but I was surprised by how much they mess with the BB height. I'm excited to get my hands on a pair of the toggle drops.

By this design, there are only three holes if you exclude the axle hole. There are two threaded holes and a dowel pin hole. The hooded pieces have additional two holes to remove mass but this is just a concept model, as the final design will be pretty up some with some creative pocketing to save weight. Thanks!

[tigoat]

One thing I forgot to mention is that those angles of the swinging arcs are very critical, as it took me a while to find a sweet spot where I can keep the vertical variation to a minimum. For this reason as pointed out from Drew, if those rockers are not oriented as originally intended, the vertical dimension can change drastically as the they swing through those arcs.

[Rody]

At first blush the dropout is reminicient of the dropout made by Peter of Whipsmart, though this compartmentalizes the rocking action, upping the efficiency in limiting movement in the vertical plane.

Cool piece, easy to see you've put in some time, it is a thoughtful design. I'd build a couple of team/non-customer frames with these to see how they work.

rody

[tigoat]

Attached is a couple of cartoons that shows a basic vibration simulation of the four common dropout types. The analysis was to determine the first mode resonant frequency of each part. It does not tell us how much these parts flex nor their stress levels but comparatively speaking, it is a useful exercise to quickly study the strength of one design over another. The rule is that the higher the frequency, the stiffer the part will be. For those who are not into the vibration stuff, just imagine the pain threshold of a person, a little pain most of us can take without saying a word, but when the pain is out of control, we would scream. The same thing applies to these parts for a first mode resonant frequency, meaning a frequency where each part will response (screaming) naturally, an inherited weak link so to speak. As shown the picture, the hooded Wright/Breezer dropout has a highest natural frequency, as it starts resonating around 6,400 Hz, meaning it is the strongest of the four. It is so strong that the tube would blow up before the dropout would give. The next strong one in line would be the slider dropout, which is no surprise here, as it is also a hooded design. The other two plate style dropouts resonate at a much lower frequency, meaning they are not as stiff as their hooded counterparts. The design of the plate type dropout is fine as long as it is no overly long. Please note that those hooded drops are so short I had to add part of stays (tubing) so they all have an equivalent triangle in order to compare apples to apples. Haven’t had a chance to run one for my new concept design yet but would expect it to be similar in stiffness as the slider.





Thanks rody for the info. Hope to see some pictures of Pete's design.