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  #41  
Old 09-16-2017, 04:23 PM
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Very nice! Surprised no one mentioned that this looks like the Coleman mini bike
  #42  
Old 09-16-2017, 10:08 PM
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Quote:
Originally Posted by gokartenthusiast View Post
Very nice! Surprised no one mentioned that this looks like the Coleman mini bike
That honestly hurt my feelings. This is not a Walmart bike... The build may include lots of parts from China, but not a Walmart bike!

Ever watch "The High Cost of Low Price"????
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  #43  
Old 09-17-2017, 10:13 AM
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Practically Identical.
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  #44  
Old 09-17-2017, 12:03 PM
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Some Snowmobile CVT tuning stuff I've been reading.
https://thumpertalk.com/forums/topic...tching-theory/

....Ideally during the shift both up and downshifting the RPM of the motor should remain constant at the RPM that the motor produces it’s Peak HP. Some like their setup to start shifting a the RPM that the motor makes peak torque and then quickly increase RPM to the point where it makes it’s peak HP. In the later scenario we are talking about a matter of roughly 1-2 seconds, so for most people they will want to simply concentrate on getting directly to peak HP RPM right away.

I CANNOT STRESS ENOUGH how important it is to know what RPM your motor makes it’s peak HP at.

Your clutches will continuously be shifting up and down (hopefully) with changing loads on the system. Only in the case of drag racing or having the sled topped out across a lake or field will it hold continuously at full shift out. This is why we want them to shift both up and down while remaining at the motor’s peak HP RPM, so we achieve the absolute most amount of power to the track at all times...
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  #45  
Old 09-18-2017, 04:45 PM
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They are picking up the minibike from the powder coater and it should ship out tomorrow.
Sweet. I think I stating planning this build in January.
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  #46  
Old 09-19-2017, 12:49 PM
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Default Shedding Weight

Made it smaller. Cuts not very clean.
I don't really feel like drilling 24 more 1/2" holes through 2" aluminum at my apartment kitchen table.
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  #47  
Old 09-19-2017, 03:07 PM
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Default Shedding more weight

I am weightless, but you can see me.
When you put me in an aluminum block, I make it lighter.

What am I???
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  #48  
Old 09-19-2017, 03:15 PM
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You're a hole. The second such accusation I have made today.
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  #49  
Old 09-19-2017, 06:19 PM
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Default Looks like a brick

28 holes 1/2" diam 2" deep.
Each hole is 0.39 cubic inches.
28 holes is 10.92 cubic inches.

I also removed 20 cubic inches from the two sides of the mount with the circular saw.

31 cubic inches of 6061 aluminum weighs 3.04 lbs (just over 1 lb worth of holes drilled).

Reduced weight from 7.85 lbs to 4.81 lbs. 39% Weight Reduction!!! I'm happy with that.
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  #50  
Old 09-20-2017, 12:01 AM
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You should have made the holes bigger for even more weight reduction.


Denny
  #51  
Old 09-20-2017, 07:17 AM
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Quote:
Originally Posted by Denny View Post
You should have made the holes bigger for even more weight reduction.


Denny
I've only got a 1/2" drill bit. I can drill 18 more 1/2" holes If i want, but I don't. I was also thinking about a stepped bit to give the plate a fancier look, but It'll be fine.
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  #52  
Old 09-20-2017, 07:26 AM
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What are you going to do with 1lb of aluminum shavings?
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  #53  
Old 09-20-2017, 07:42 AM
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Quote:
Originally Posted by ezcome-ezgo View Post
What are you going to do with 1lb of aluminum shavings?
Thinking about stuffing a pillow. Or maybe get the $0.65 at the scrap yard. lol

I'm being confined to my bedroom at the moment. Entering the kitchen and proceeding to the living room requires changing clothes, wearing shoes, and safety equipment.

It was a pain. I want to get this cleaned up and never see it again. I only had motor oil for lube. After about 6 holes, the aluminum was too hot to handle with bare hands. Not sure I was drilling at the right speed. The shavings got wound up really tight and and get lodged in the tip of the drill. I had to stop every few seconds and clean the bit. My drill press doesn't exactly drill two inches deep with the 1/2" bit. It pokes through on the other side, but I still had to flip it over and finish. I was afraid that the bit would be useless or the belt on the drill press would go before I finished.

It did pretty good... when cool. Not so much after the belt and piece were hot.

I didn't drill any pilot holes (except for the the first 4 bolt holes). All of the holes except for the corner ones were drilled with just the 1/2" bit.
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  #54  
Old 09-20-2017, 07:58 AM
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I'm not going to ask you what you were thinking. Once you had roughly 8lbs of aluminum in your hand, it was only a matter of time before GAB happened. But you know... real weight reduction would come from drilling through the block horizontally now.
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  #55  
Old 09-20-2017, 07:59 AM
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Minibike should be here on Saturday. I'm working doubles Sat and Sun, so hopefully I can get at it next week. I'm already thinking about how to modify some of the parts.

I've been told the pegs don't hold very well. They slip and rotate, so going to replace the TWO bolts (one for each clamp-on style peg) with ONE long piece of SS threaded rod (through both pegs). I'll put 4 nuts on the rod. That should keep them tight and prevent them from rotating. maybe I'll paint some round tubing to cover the threads on the rod.

Saw it Here...
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  #56  
Old 09-20-2017, 08:02 AM
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A very KISS solution.
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  #57  
Old 09-20-2017, 08:17 AM
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Let's play a game...

Bike ~50lbs???
Engine ~38lbs???
Tor. C. ~12lbs???
Bob ~170lbs
Al Blck ~8lbs

277 lbs (125.65 kg)
274 lbs (124.28 kg)

Removing 3 lbs of weight from the block reduces overall weight (mass) by ~1%.

F= ma <---- Good for at least 1 pt partial credit on every Physics homework, quiz, or test in the universe.

Less mass = more acceleration.

Torque at axle = 15 lb ft (at crank at 4000 RPM) * 14.47 (Gear ratio at 4000 RPM) = 217 lb ft
Linear Force = 217 lb ft / 0.542 ft (radius of tire) = 400 lbs of linear force

400 Force lbs = ~1780 Newtons

F=ma
1780 Newtons = 125kg * a

So Ideal Acceleration at TC engagement would be
1780 Newtons / 125 kg = 14.24 m/s^2

Figure in about 20% loss, so we can assume 11.4 m/s^2

1.16 g instantaneous acceleration at launch????? Sounds reasonable.
Prepare for launch
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  #58  
Old 09-20-2017, 08:35 AM
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So reducing the mass by ~1% improved the acceleration ~1% ? More precisely 0.989% ?
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  #59  
Old 09-20-2017, 11:45 AM
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Quote:
Originally Posted by ezcome-ezgo View Post
So reducing the mass by ~1% improved the acceleration ~1% ? More precisely 0.989% ?
% Change of a value is calculated by dividing the "change" in the value by the original value and multiplying by 100.

((125.65-124.28)/125.65)*100= 1.09% decrease in mass

80% of 1780 N is ~1424N

1424N = 125.65kg * a
a = 11.33m/s^2

1424N = 124.28kg * a
a = 11.46m/s^2

((11.46-11.33)/11.33)*100 = 1.15% increase in acceleration
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  #60  
Old 09-20-2017, 11:57 AM
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I'll drink to that.
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