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Hi justcrankin
Originally Posted by justcrankn
(Post 11004499)
This sounds like a great adventure.
1. Is the frame whippy? Will it be able to develop oscillations under certain conditions? This is something you wouldn't worry about on most singles. Gosh I hope not! That is something I have yet to consider. Any ideas on what I can to to remove that possibility from this bike? 2. How are you carrying gear? Rack, panniers, bag over the top tube, etc? What will the front/rear weight distribution be? Weight distribution will be a challenge for sure. I am making a set of panniers for the rear, and have to decide what will get carried up front. In all actuallity, the weight shouldnt be more that having a stroker of the same weight as me onboard, except that the weight will be much lower, and more rearward, centered over the rear wheel. I intend on saving weight any way I can when it comes to the cargo I carry. 3. Is the rear brake up to the job? That's your first line of defense if the engine goes nuts. Are parts readily available? I'm assuming the engine won't provide any engine braking. The rear brake is NOT up to it. I am playing with a few ideas to solve that, which I believe is my most important problem to get solved. There will be several kill methods for the engine so I dont have to out-brake a possessed engine. And nope, I wish it could offer some engine braking, but it wont. The concept of using the longer wheelbase for this setup makes a lot of sense, as long as the weight is reasonably balanced. I wonder about the durability of the wheels and rear hub. 25mph sounds suicidal. Will it have enough power to climb the hills? That would be a huge load to pedal up a mountain. Why do you say 25 sounds suicidal? I am used to off road downhill descents at +35, so fast that the gyroscopic effect on the wheels made it difficult to steer. Now THAT was suicidal! Man was I glad to have disk brakes then!! Help me understand. I do know there is a tipping point of sorts, a narrow window where sane rapidly translates to insane when we talk about speed. Am I on the "OMG" side of the tipping point as 25? As for power, I have a solid surplus of it with the engine I am using. And I reeeeeeeeally hope to not have to use the meat motor up the mountain! Be sure to bring your insurance card!!! |
Man Tandemgeek, thats a SWEET ride! I want one! tho it looks super heavy! Still awesome! I agree, ride what u like and like what u ride! Thanks, again. You r a class act.
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Originally Posted by WebsterBikeMan
(Post 11004182)
Actually it's worse than that. The rules of whether it's legal on the road will vary from state to state. As far as I know it is not legal in NY. I wouldn't begin to conceive of a reason why, but electric assist bikes aren't, and I'd have to guess this is in the same category. As for whether anyone would stop you, I have no idea.
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I don't know but the legality of the bike, whether it's registered or not may or may not be a problem. I saw a ton of hill folk and people in the west riding quads all over the place. Going to the store, buzzing around town, whatever. No authorities seemed to care and very few, if any were registered. The appearance of this bike may cause some unwanted interest from bored small town cops and such like. A smile and lots of humor may be the way. Good luck!
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Moped laws vary from state to state, including the definition of the vehicle. To determine the laws that apply to your vehicle, you must know the engine size and its maximum speed. 50cc or less with a maximum speed of 30mph seems to be the threshold in most states.
This is a good starting place to establish what laws apply to mopeds in specific states. http://www.moped2.org/mstates.htm The now popular electric-assisted bicycles are also subject to maximum watt / speed capabilities, e.g., 1000 watts in Georgia with a maximum motor-assisted speed of 20mph, i.e., the motor must be governed at 20mph regardless of how that speed is achieved, power-alone or in combination with rider pedal inputs. More info is out there at sites like this one: http://www.pedegoelectricbikes.com/e...icycle-laws/46 As noted by foamy and others, enforcement is typically non-existent (much as it is for cyclists who don't adhere to the rules of the road) unless someone draws undue attention to themselves in the presence of a law enforcement officer, who may or may not be all that well-versed in the laws as they apply to bicycles, electric-assisted bicycles or Mopeds. |
Yeah, the legality will be a constant concern, but from all my research on the subject says that, like TandemGeek pointed out, enforcement is minimal and spotty. Unless the local PD feel the need stop me, I expect that I will either be ignored, or talked to from a curiosity perspective. I'm just a guy riding thru town is all :) Sweetness and guarded honesty is my policy. Here in Michigan, others with bikes speced like mine were registered as a moped. When u have a vehicle with 2 totally independent forms of propulsion, and one is the human body, people tend to be confused. The pedals make them want it to be a bicycle. Which of course, it is.
This is a great thread, with some great dialog, so I don't want to quell that. I am just wondering if there is anything else to be said on the original subject of Tandem Handling? Thanks |
Originally Posted by LordKeiella
(Post 11006416)
I am just wondering if there is anything else to be said on the original subject of Tandem Handling?
For example, someone voiced a concern about 'frame whippiness' which can be a concern on a double step-through tandem frame like yours. However, without having a person sitting on the back seat moving around and putting loads into the frame at the top of the seat tube via their saddle the equation changes. As to how it will change, that's dependent on where you install your motor, fuel tank and carry your luggage. It could be that having all of that weight suspended from the rear 1/2 of the frame will have less influence on frame stablity... or it could have more if the weight is carried too high. You won't really know until you can do some trials with the bike fully loaded, at which point some additional frame bracing may be needed, e.g., adding marathon-like stabilizing tubes running down both sides of the frame from the captain's seat tube mast cluster to the rear drop-outs. In fact, the more I think about what you are proposing the more I'm inclined to suggest you spend your time corresponding with folks who have fitted single bikes with the Xtra-Cycle cargo bike rear extensions or who have a Surley Big Dummy, and in particular the ones who have also installed a Stokemonkey electric-assist motor... as that will have more in common with your tandem configuration than what most of us ride. They can also address brake performance, etc.. as the typical problem you face riding a tandem solo pertains to the loss of weight on the rear wheel and having the center of gravity sitting well forward of where it would with an adult-size passenger, again subject to how much weight you'll be carrying over the rear wheel on your loaded tandem. http://farm2.static.flickr.com/1358/...165e7cb5d7.jpghttp://www.surlybikes.com/blogimages...y_dummy_lg.jpg |
The possibility of a whippy frame is what would concern me the most. The frame on our production tandem is solid. We frequently hit 45 mph on our local hills and there are no stability problems. The frame on your tandem just LOOKS unstable, FWIW. Being homemade makes you the test dummy. Adding a motor adds some new dynamics with vibrations and torque reactions. The faster you go the more some unknown harmonics could take control of your rig. I'm not trying to discourage you-just be aware of the possibilities. If you're like any other red-blooded male, the first thing you'll want to do is see how fast it'll go. Tandemgeek described one way to beef up the frame.
Your MTB riding is drastically different because YOU are 90% of the weight on a short-wheelbase. On the tandem you have a load to control through the frame. Every steering input and weight shift you make controls the rest of the load. If the frame is soft, it would be like having all your bike inputs spring loaded. Can you add a rim brake to the rear for a total of three brakes? You can't please all the bike snobs, but who cares! Disclaimer; no direct experience here, but I did install a gasoline washing machine engine on a bike many years ago. Your rig looks much safer. |
Originally Posted by Xanti Andia
(Post 11003181)
So said some of the people who attempted baloon rides on lawn chairs, though your endeavour seems more feasible. Good luck.
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Hi justcrankin,
The frame is unidentified, but I dont think its homemade. The more I read about this "whippy frame", the more I am considering beefing up the frame. Fortunately, I am very unlink other males. I know exactly how fast it will go. 25mph. No faster, it will be geared for 25 at redline. Any faster and I better start looking at brand new components, and heavy duty components, and I dont want to have to do that! I am considering a disk brake mounted on the left side strokers crank with a chain drive back to the rear wheel, so I have the band brake, disk brake, and rim brake on the rear. I'm hoping that, and a strong center-pull for the front, will provide all the braking force needed.Thanks Keith |
Are you ditching the band in favor of the disc? Would the disc have its own chain going back on the left?
Have you had the hub apart? It's a longshot, but if you could modify the stoker input so it doesn't freewheel, then you could 1)get a tiny bit of engine braking 2)use the stokers drive chain for the crank mounted brake. Edit;nevermind the fixed gear idea, the engine wouldn't freewheel when you wanted to just pedal. |
Photographs of motorized tandem here.
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Originally Posted by LordKeiella
(Post 11020295)
Hi justcrankin,
The frame is unidentified, but I dont think its homemade. The more I read about this "whippy frame", the more I am considering beefing up the frame. .....Thanks Keith Good luck and keep us posted. |
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