# Drawbridge for bikes.



## leoferus (Jul 22, 2011)

Has anyone seen a bike actuated drawbridge? I was just wondering if more creative individuals have ever come up with a bridge that can be actuated from either end by a bike riding onto it. Thanks.

The best I can come up with is two teeters attached with a pulley system.


----------



## swampboy62 (Feb 10, 2009)

I almost hate to ask...

Are you talking about a bridge that would be up, then as you rode on it would descend to normal bridge position?

That could be done, but it would be easiest if it was one directional travel. Two directional would take extra work for sure.

Steve Z


----------



## leoferus (Jul 22, 2011)

Yes! We are being ambitious. Unidirectional is easy. Bidirectional is a bit more work. I have a solution but i wanted to probe the community as well. I'll post what i have in mind when i get home. Thanks.


----------



## Moustache rider (Jun 1, 2007)

Here is something I came up with on the fly. Should be fairly simple to build.
Why do you need a draw bridge anyways?


----------



## leoferus (Jul 22, 2011)

Excellent! Thank you. I'll post mine as soon as I can. 

I don't need a draw bridge. It was an idea a friend had. I'm just trying to solve the problem. We figured it would be a cool entrance to a skills section of trail.


----------



## dl1030 (Sep 3, 2009)

why not tie the teeters together on one end? no pulley needed. Maybe I am not understanding the end goal....


----------



## leoferus (Jul 22, 2011)

All ideas are welcome. Sketches are appreciated. There is no wrong way of doing this. We just want the least amount of moving parts. My idea falls along the lines of what was posted above minus the pulleys.


----------



## Moustache rider (Jun 1, 2007)

Here is another one. Attach chainrings to both bridge pivot points. Connect enough chain together to reach around both chainrings and cross them in the middle.


----------



## mtbAndy (Jun 7, 2004)

Here's my very rough sketch. This isn't to scale and all that stuff. For simplicity it's drawn as one-way but the same rigging from the opposite direction should allow two-way traffic.


----------



## robbiexor (Aug 22, 2011)

I like the simplicity of Hillybilly Hank's drawing. Just remember to add the appropriate counter weights. I don't see why it wouldn't work bi-directionally though.


----------



## mtbAndy (Jun 7, 2004)

robbiexor said:


> I like the simplicity of Hillybilly Hank's drawing. Just remember to add the appropriate counter weights. I don't see why it wouldn't work bi-directionally though.


Counter weights or off center pivot works too. The teeter in my yard is off center but it's easy enough to screw some extra boards on to adjust weight as needed.


----------



## leoferus (Jul 22, 2011)

It doesn't have to be exactly like a draw bridge. Just similar. With a pylon in the center of the crossing and no pulleys... A criss-cross overlap system could do the trick.

Keep the designs coming. I'll design this in 3d when i get a chance. Thanks all.


----------



## Ridnparadise (Dec 14, 2007)

It's not going to be easy getting the Queen Mary under those bridges


----------



## leoferus (Jul 22, 2011)

I forgot to mention that canoes and kayaks must fit under the bridge.












Just kidding.


----------



## arkon11 (Jul 26, 2009)

Why would you want something like this on your trails?


----------



## leoferus (Jul 22, 2011)

Reasons stated above. I want all sorts of crazy stuff I probably won't get approved. The cool thing is that if I don't get approval I will build it in my back yard.

Short answer. Because it's different, ingenious, a good filter for advanced skills sections, etc. And, of course, this trail section would be a branch and not a main line.

Shorter answer, because it's cool. And because I already got a no to build a hamster wheel.


----------



## Trail Ninja (Sep 25, 2008)

A quick image search found this at Whistler on "A River Runs Through It". This means it's been done and approved by a team of lawyers. That's good news for you.


----------



## Fattirewilly (Dec 10, 2001)

Trail Ninja said:


> A quick image search found this at Whistler on "A River Runs Through It". This means it's been done and approved by a team of lawyers. That's good news for you.


Yeah, but if you have an IMBA Club/Chapter's insurance policy, which doesn't allow teter-totters because they have moving/articulating parts, I don't see how this will be insured either.


----------



## Trail Ninja (Sep 25, 2008)

Fattirewilly said:


> Yeah, but if you have an IMBA Club/Chapter's insurance policy, which doesn't allow teter-totters because they have moving/articulating parts, I don't see how this will be insured either.


No, it wouldn't. It's definitely a teeter. The "Whistler did it" argument might help in other cases but if your insurance forbids it, you're out of luck. I'd never get that approved in any of the public parks I build in. I've never built a municipal skills park but I see things in some of those parks that my parks would never allow.


----------



## Joules (Oct 12, 2005)

when you say "drawbridge" are you simply talking about 2 teeters (that move through whatever angle) that articulate together, or do you mean something that actually opens wide enough to allow some one or something to pass through the space? 

Seems to me like a dual-teeter, the second half is really just there to make it intimidating, or ridable in both directions is a different design problem than something that's meant to open up enough for something to pass through. 
If you were really building a draw bridge, and the opening was for boats... that would be the coolest thing ever.


----------



## leoferus (Jul 22, 2011)

This is purely academic. But thank you all for the supportive and negative feedback. The objections are all of great concern. I wouteeters that build anything I don't have approval for. I'm just an enthusiastic builder that cannot, unfortunately, devote time to tOur administrative side if things. Having said that, there is a skills trail in one of our parks. This was state approved. The new master plan has extended it. Therefore, the possibility for new features exists. Currently, two tweeters are there. As a result, the proposal of another set of tweeters that happen to create a bridge might not be such a difficult thing to get approved. 

I'd rather design it and have it rejected as a complete idea than have it shot down as a result of poor presentation.

So, for our purposes here, this is an academic endeavor. Thank you all!

Besides, nothing stops me from building in my backyard.


----------



## leoferus (Jul 22, 2011)

Joules, 

I like how you think. I want one that well allow traffic underneath. Mutual actuation of two articulated ramps. Muahahaha!


----------



## jmitchell13 (Nov 20, 2005)

How about this? Two teeter totters connected at the end with a pin/slot mechanism. As one goes down, it pulls the other with it.
They would need to lock together when full down. I'll try to sketch that up when I get a chance later.


----------



## leoferus (Jul 22, 2011)

I like it. It might not be exactly what I'm looking for but I like it.

I was thinking of something similar but with extensions that interlock to pull the other down.


----------



## bamwa (Mar 15, 2010)

this could work if accessed from one direction

when I think drawbridge Im thinking castlestyle. one sided.

good luck


----------



## Trail Ninja (Sep 25, 2008)

jmitchell13 said:


> How about this? Two teeter totters connected at the end with a pin/slot mechanism. As one goes down, it pulls the other with it.
> They would need to lock together when full down. I'll try to sketch that up when I get a chance later.


I like it too. I'm going to build one. A pillar in the middle will eliminate the need for a lock in the down position, but a plate or bar on the bottom between the two right side stringers that the left stringers could land on might work. If it's only for bikes or foot traffic it won't matter if it's a little flexy.

Edit: Duh! the stopper goes on the back to keep it from lifting too high.:madman:


----------



## jmitchell13 (Nov 20, 2005)

Trail Ninja said:


> I like it too. I'm going to build one. A pillar in the middle will eliminate the need for a lock in the down position, but a plate or bar on the bottom between the two right side stringers that the left stringers could land on might work. If it's only for bikes or foot traffic it won't matter if it's a little flexy.
> 
> Edit: Duh! the stopper goes on the back to keep it from lifting too high.:madman:


Post pics if you ever build one, I'd love to see it!
My thoughts on the stop would be to extend the right hand stringers a bit longer, and mount a stop on the underside of the left hand stringers that extend out beyond them.


----------



## ghglenn (Jan 26, 2012)

You could build criss-crossing teeters that span the entire distance each direction. 
Visually they would have a cool scissor-effect to them.


----------



## Diesel8810 (May 17, 2012)

*I love this!*



Moustache rider said:


> Here is another one. Attach chainrings to both bridge pivot points. Connect enough chain together to reach around both chainrings and cross them in the middle.


So this got me thinking.... Using the Chaining and chain idea I set off making some sketches and came up with one common issue - How to have the rider weight rotate a chainring and chain and in turn reverse the motion on the other drawbridge arm... Well after a little thought I realized that you would need an exchange gear to reverse the rotation for the other side... Then what popped into my head was a cars rear axle / rear end... In order for the single drive shaft to turn the wheel in the same direction the it must exchange that common of the driveshaft in opposite directions on each wheel.. So if you remove the driveshaft from the equation and just figure that turning the one wheel one way it in turn spins the other wheel the other way... So the drawing below is what I came up with.

There would be several variables to work out: Gearing, keeping everything lubed, weight needed to turn gears (weight minimum/maximum)?.. and several others... This was just a quick sketch,,,

I would love to get to build a small prototype if I had any extra time... But I barely have time to get rides in these days...

Disclosure: I am not an engineer or car mechanic so this is all based on a little theory and a lot of tinkering when I was younger... That being said any Engineers or Auto Mechanics out there please feel free to chime in... I would love to know if this would work..


----------



## singlesprocket (Jun 9, 2004)

one way drawbridge...


----------



## Trail Ninja (Sep 25, 2008)

singlesprocket said:


> one way drawbridge...


Have you ever ridden the Canal Days MBR in Port Colborne? I bet I could find all the parts for one of those in "The Hood"


----------



## bamwa (Mar 15, 2010)

Diesel8810 said:


>


He needs canoes to be able to go under.


----------



## Diesel8810 (May 17, 2012)

bamwa1 said:


> He needs canoes to be able to go under.


I believe he was just kidding (at the bottom of his post about kayaks and canoes).. Also I am local and ride the area he's referring to weekly so if I am not mistaken there isn't much kayaking or canoeing done where he is referring to.. That being said you got me thinking and I went back and reconfigured it (albeit more materials, more building and a bit more complex) so that the car rear axle is simply above leaving the water way / ravine below unaffected...


----------



## leoferus (Jul 22, 2011)

Diesel8810 said:


> I believe he was just kidding (at the bottom of his post about kayaks and canoes).. Also I am local and ride the area he's referring to weekly so if I am not mistaken there isn't much kayaking or canoeing done where he is referring to.. That being said you got me thinking and I went back and reconfigured it (albeit more materials, more building and a bit more complex) so that the car rear axle is simply above leaving the water way / ravine below unaffected...


I was kidding about the kayaks and canoes. But I don't want anyone to be discouraged from exercising their imagination. So far, the designs have been amazing. Keep in mind that it is likely I will not get permission to build this. Also, keep in mind that it would be cool if we could build it. And if we did build it, it would be even cooler if we built it so that one could ride under it. My new idea is to have the bridge spiral unto itself and under the drawbridge section. So you can ride up the spiral and over the bridge or over the bridge, around the spiral, and under. Thank you all.

I'm sorry that I have not contributed much. If you look at the regional posts, you'll see I am busy repairing trails due to Sandy's temper tantrum. Tonight I am driving to NY to deliver relief goods to FEMA/Red Cross. Tomorrow morning I'm working on local trails again. The rest of the time I have to work. Any spare time after that is spent riding. Yes, I ride sometimes.

Thank you for your contributions and your patience.


----------



## bamwa (Mar 15, 2010)

^ Nice that's funny as ****!


----------

