hillzofvalp wrote: I did get four ~7/4x1/8x4"arms made which have terribly drilled holes. Even when I used the whole punch it went off a little.
The club I'm participating in is new at Purdue University, and you can check it out at electricvehicleclub.org, which was only put up couple of months ago. Many of the senior members are affliated with Purdue's evGP electric go-cart racing, so I suspect my future prototypes will come together well after having gaining access to machinery and guidance in the engineering building.
Actually, the brand new machinery rooms at purdue are very sophisticated, and they even have job openings. I plan on applying soon so I can learn to use their cnc and maybe even their water jet machines someday. Pretty cool oppurtunity, and, if I major in Mechanical Engineering, it will look really good on resume .
LUCKILY, my frame is pretty big at 59cm, not to mention they're 1" 1/8" tubes, also giving me extra room. I will try out the template today and get back to you, but I still haven't ordered a motor or esc yet. Waiting to see what club thinks. Btw, could/did you experiment with different tire widths?
hillzofvalp wrote:My question about tires is more along the lines of: Will a 28mm, wider tire, work better? Maybe ideal tires or tire pressures could be investigated. how much surface area contact is ideal? .
adrian_sm wrote:Not sure. I think it was Kepler that said this is the optimum engagement, to be able to draw the straight line between motor pivot, contact patch, and wheel hub. I don't quite agree and have been setting up my drives to limit the travel before that point with success.
I think I outlined my reasoning in this earlier post. But I have not totally convinced myself so take it with a grain of salt.
I can still have the same amount of engagement with the tyre but at an angle. The allowable angle is dictated by the coefficient of friction between motor and tyre. Come to think of it this will be the worst when the motor is first coming in contact with the tyre when you will have the largest angle. This could be improved by increasing the radius at whcih the motor pivots.
Damn. That is a good argument for a longer pivot arm.
Funnily enough now that I have a single pivot arm, I could fairly easily do this by placing my pivot point infront of the seat tube, and having a longer pivot arm. Hmmm. It would increase weight, but may help avoid slip during initial pick up. But it would also require the drive to pivot further to have the same engagement into the tyre. So it wouldn't help trying to get it on smaller framed bikes. Damn.
From my understanding of the geometry, the most critical time it will slip is during initial engagement for the pivoting designs like mine and Keplers. Once it gets over that point the geometry will only be able to apply more contact force until it is limitted by a force balance, or deadstop. If you slip at the fully engaged position you would need to adjust the drive such that you acheive more engagement, ie. lower the drive, or adjust the deadstop.
To directly answer your question. Yes the geometry of the frame does limit the travel of the CB, and could restrict engagement. But you don't need to aim to have a fully straight line between motor pivot, contact point, and rear wheel hub. You can stop short of this and have just as much tyre engagement.
P.S. One of the other reasons I don't let the drive pivot that far, is that you see a drop off in the torque required to maintain the drive in that position as you get closer to the straight line. This means the drive suddenly accelerates its rotation towards the deadstop, and hit is with a bit of a clunk. I was previously just adding a dampening material to my deadstop, but by adjusting the geometry I effectively used the compliance of the tyre to do the job instead.
Love your bike build and writeup! Do you have a link for the triangular bag on your white road bike?
Kepler wrote:Having the pivot on the opposite side will certainly open up some bike frame options.
Kepler wrote: Be careful not to step on some "hidden" patents though
Kepler wrote: ... Be careful not to step on some "hidden" patents though
adrian_sm wrote:I think I am more worried about infringing on John's (Kepler's) design.
There are heaps of differences between mine and the other "hidden" design
Theirs has a one way bearing, mine mechanical disengages
Theirs has an in-runner motor mounted infront of the tube, mine an out runner behind
Theirs has belt drive with reduction, mine direct contact.
Mine uses rotational inertia reaction to engage the tyre, theirs remains in contact
The main common ground is the pivot mounted to the seat-tube, but I can't see that being an individual claim in the patent.
I think I am clear.
adrian_sm wrote:Perhaps you were looking for one of these
TD, thanksTylerDurden wrote:
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spinningmagnets wrote:Motors: the 63mm Turnigy with a skirt bearing and a 200-kV is proving to be popular, but keep in mind that before rushing into that one, Kepler is testing the similar 63mm Aeolian motor with a 170-kV, results to be posted soon.
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