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Thread: Bike Physics


  1. #1
    AtomRC's Avatar
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    Bike Physics

    I saw a thread about this on here a while back, but I don't remember what ever became of it.

    So, let me ask, if not only to add more content to the forum.

    First, some background. I ride a real motorcycle. I'm sure some of you may to. If not, you know what i"m talking about anyways if you've ever watched a motorcycle race.

    So, on a real bike, the faster you get going, the harder it gets to turn. So much so, that in races, the riders rely more on there body postion to turn the bike than they do the bars.

    I notice in stock form, the HOR is very slow to react to rider input. My guess is because the rider weighs next to nothing compared to the weight of the bike. In the post I remember reading, the general consensus was to try and add weight to the top of the bike to help it turn. For example geting the aluminum or steal rider stand or seat or even making something up. Theoretically, this should not make any difference. Although the CoG get's higher making it more tippy, the bike gets heavier and hence the rider would make even less of a difference. The higher CoG also would make it less stable at low speed.

    My thinking would be to pack the inside of the HOR's torso with CLAY or similar heavy material to increase his weight. Thus, when he hangs off the side, there is a bigger weight (force) pulling it down not to mention moving the CoG to that side of the bike and even slightly lower than when upright. The lower and now off center CoG may even make it even more stable in the turn.

    Has anyone tried this? does it even make sense?

    btw, does anyone know how i change where is says I'm from in my Profile? I'm not from Bulgaria. In in Ottawa, Canada.

  2. #2
    grymg's Avatar
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    RE: Bike Physics

    Hopefully I can add to this discussion –

    First and foremost I believe motorcycle racing is the one of the most exciting forms of motorsports, not because of the trick machinery, but rather because there is more emphasis on the rider rather than the quality of the machine. You also get to see the rider at all times and his body position to see how he controls athe bike and how he reacts to problems.

    With that in mind, in real life the rider shifts CofG into the corner and leans off of it to hold it there at the higher speeds but to initiate the turn there is significant bit of input from the handlebars. First turn the handlebars to offset the bike, then the rider finishes it off.

    With the HOR you see this concept. First the forks are upset, then the lean of the rider takes over. There have been many experiments done to illustrate this: 1) In the bike w/o rider attached, the bike can be upset, but not turn because the rider has a lot to do with the CofG shift. 2) In the bike w/rider but also w/the forks free to wiggle however they want, the bike turns, but is slow to be upset!

    Ok, so with these experiments the rider weight is an issue but not as important as the front end that initiates the turn in my experiences. I have added weight to the rider to help response but having a front silicone insert w/o metal flywheel in the front tire made the most difference. It takes up all of the space in the front tire, leaving no empty patches so it acts sort of like a wedge now. And with the metal missing the lighter front end is more agile. Note: the harder the compound rubber, the faster your response will be but you will also be prone to more front end wiggles because of the lesser contact patch.

    I’d appreciate anyone’s comments! Makes for a good discussion.
    Ian
    Radio Control Motorcycles Club of California
    rcmcc.tripod.com

  3. #3
    AtomRC's Avatar
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    RE: Bike Physics

    I see. Did the heavier rider help even a little? The reason I ask, is because it is possible for me to completely steer my real motorcycle without touching the bars at all. Same with my bicycle. For example, if I'm cruising down the road at 100Kph or so, when i come to a corner, i have the option to either push the bar on the side i want to turn (counter steering) or, not push or pull at all and just hang my ass off the side. If i hang my ass off the side, the bike does the rest. The only reason my hands are even on the bars is to keep from falling off. Howver, one thing that's different on the HOR is that the forks swing from side to side about 15 degrees in either direction. Obviously, a real bike doesn't do that. I'm thinking Kysho makes the front swing like that to make up for the light wieght rider. Most rider's in real life weight about 1/4 of the weigh of the bike. This is assuming the rider is 100lbs and the bikes, like most high end ones these days, are 400lbs or lighter.

    I just had a thought. I bet the reason the front of the lower fairing drags is due to that 15 degree swing of the front forks. ie, when it swings to the right, the bike leans left, however, because the front forks are not centered, the lower front fairing actually dips lower than it would on a real bike. If you could keep the forks center like a real bike, it may give you that wee little bit of clearance up there needed to clear the fairing in a corner.


    Where are you guys getting these sililcone inserts? are you making them yourlseves? I'm all the way up here in Canada, so I don't have the same access to local guys down in Cali like alot of you. Is there any relatively easy way to make the silicon inserts? I read the paragraph about them on your website, but it looks pretty difficult to do it myself.


    what if I just fill the tire with shoe goe, mount it and let it set? I already read about getting some D shaped foam from the local harware store, but the silicone inserts seems like it would be much much better.

  4. #4
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    RE: Bike Physics

    I see what you're saying, with the rider movement on real motorcycles. Someone in our club did the experiment on the HOR where he had a silicone insert upfront, but locked the steering head to not swivel and left the triple clamps loose to turn just like what you do in real life. The servo control was only the rider leaning back and forth. And the result was a really slow turning bike. I think it just wanted to go straight and not turn at the relatively higher speeds.

    Silicone inserts are great to have, I learned this after joining the yahoo radiocontrolmotorcycles forum years ago. Everyone there used them, and their pretty good tinkers. After much tinkering myself haven't been able to find anything better than the inserts I bought on that forum a long time ago.

    However no one makes them anymore.

    The silicone insert from the paragraph sounds hard to make but the difficulty is mileading I think. I've seen it done before and all it took was a spare rim and tire, put a hole in the tire, then inject silicone into it with a plastic syringe. Let it cure and when you peel the tire off the rim the silicone mold should pop right out. Then take an exacto knife and trim off the excess, clean off the tire internals and you can make another!

    The only part I am unsure of is the brand/type of silicone used. If I knew I would make them for you.
    Ian
    Radio Control Motorcycles Club of California
    rcmcc.tripod.com

  5. #5
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    RE: Bike Physics

    Shoo Goo could work but it's very viscous (slow flowing), so it will be a pain to inject that much shoo goo with a syringe.

    Foam works well too for bike response, I've tried it. But the problem is that it's too light so you get to see the front end wobbling sometimes. For those of you who don't have inserts I suggest going with the optional lightweight flywheel with round 1/2"dia. cross section foam cut in half to fill the contour.
    Ian
    Radio Control Motorcycles Club of California
    rcmcc.tripod.com

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    RE: Bike Physics

    yea, i guess the shoe goo is to thick for injecting. I can't think of what else to try that is eaily injected. I have the lightweight flywheel, so I gues I'll go with that and the D foam.


    As for the whole rider thing. If he had locked down the swivel and rely'd soley on the rider to turn, i can see why it was slow. You still need to intiate the turn.

    This is what I am going to try:

    1) lock the swivel so it doesn't sway side to side
    2) add CLAY (cuz it's heavy) to the rider's torso
    3) implement the direct steering mod

    The direct steering should make up for the lack of swivel in that regard and then the hole set up THEORETICALLY should perform more like a real bike.

    Using a static test, if I full lean the bike to the side, if the front wheel is centered, and not swiveled to one side, the lower fairing does not apear to touch down. It's only when the front end sways to one side that the fairing scrubs.

    I still need to get some peices for the direct steering so it will be awhile before I can try the test. I'll let you know what happens. I think it would be the combination of the direct steering and weighed down rider that would provide the best results. At the very least, the heavy rider may make it more stable in the turn because of where the CoG ends up being.

    thanks for the feedback.

  7. #7
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    RE: Bike Physics

    wait a minute, does the rider still "hang" off the side with the direct steering mod? Or does he just sit there?

  8. #8
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    RE: Bike Physics

    The fairing will scrub with swivel steering but not direct steering. That's why you see a lot of bikes running without the lower fairing using the stock steering system. But it's a bit hard to do direct steering with the HOR to keep the moving rider intact! Basically several ways to do it:

    1) put one servo for steering and leave the stock servo in place just to move the rider.
    2) create a "bent piano wire" system that controls both at the same time.
    3) create a "push and tug system" with a wire using the stock servo

    I have limited knowledge on this though, however three people in RCMCC have direct steering Kyoshos. I'll post pics. Remember though that all of these methods have to be either spring or rubber band loaded to create play in the steering.

    Oh and I forgot with direct steering you need no silicone insert because the response is very quick. I run with one on my DS bike but the response is fast already, so no need.


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    Ian
    Radio Control Motorcycles Club of California
    rcmcc.tripod.com

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    AtomRC's Avatar
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    RE: Bike Physics

    well, I'll see if I can get option #2 to work. Getting the one servo to control both through the use of linkages.

    those pics are great. I also have a couple other's to use as a reference.

    I let you know if it was a success or not. But give me a month or so. Unfortunaly, work comes before play. It'll be hard for me to test it out too, seeing as how in a month I"ll have about 1ft of snow outside.

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    RE: Bike Physics

    Hello Atom; To change our (Bulgarian) address click on "my account" it's just above the cub picture in the RC Universe header. That'sll take you to a page where you can change Bulgaria to Ottawa.

    Is there any Nitro powered Motorcycles available yet? Where do you run these things? Are there any four strokes used in Motorcycles?

    I ride a BMW R100/7 about 36,000 km. a year here on the 'wet coast" and have always been curious about RC motorcycles.

  11. #11

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    RE: Bike Physics

    Donkey doctor, I ride an ST1100 and a little CBRf4. I got in to r/c bike 8 or 9 years ago and have moved up to the 1/5 scale bikes. All I can say is if you like full scale bikes and are curious about r/c bikes--GO AHEAD AND GET ONE! They are a blast to run, and work on and hop up and modify! Also check out RCGrouops.com motorcycle forum! That's where all the bike guys hang out!

    STeve B in NC

  12. #12

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    RE: Bike Physics

    Donkey doctor,
    I ride an ST1100 and a little CBRf4. I got in to r/c bikes 8 or 9 years ago and have moved up to the 1/5 scale bikes. All I can say is if you like full scale bikes and are curious about r/c bikes--GO AHEAD AND GET ONE! They are a blast to run, and work on and hop up and modify! I have five 1/5 bikes now, and 12 r/c bikes all together, and enjoy the little bikes as much as I do the big ones!

    STeve B in NC

  13. #13
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    RE: Bike Physics

    Hi guys,
    Had some of these bikes for quite some time but have been afraid to run them since there weren't many parts to fix things. I just ordered a brand new one with full aluminum options and a new Mamba brushless system so we'll see how it works.

    This is for both grymg and AtomRC. It concerns the silicone you guys were wondering about. It's called OOMOO 25 and is available here: http://smooth-on.com/liqrubr.htm

    I can't take credit though. Found all of the info and tons more on the California Motorcycle clubs site here: http://rcmcc.tripod.com/id19.html

    Hope that helps and keep the good discussion going!
    5150

  14. #14
    grymg's Avatar
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    RE: Bike Physics

    Thanks for the links!

    Are you selling inserts?
    Ian
    Radio Control Motorcycles Club of California
    rcmcc.tripod.com

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    RE: Bike Physics

    Not selling the inserts at this time. We'll see how it goes. If it's easy enough and I have left over silicon I would be into hooking you guys up.

    So back to the steering set ups. I have seen a ton of pics and vids with people not running the lower fairing on the bike. Is that the only way to run them with the stock steering set up? If that's the case that sucks and I'll be going with the direct steering option also. Would be an issue for the rider though.

    Not that it would be worth doing anything but I wonder how it would work to have an additional mini servo that controls the rider and then have him on the 3rd channel of my FM. This would allow you to throw him off the side and really test what kind of weight factors he really causing on the bike. Just a thought.....

    5150


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