KIRK Posted November 18, 2012 Share Posted November 18, 2012 fuck just download that calculator I told you guys and all you guys wouldn't of built bikes that didn't move lol. its fucking simple and accurate azz Quote Link to comment Share on other sites More sharing options...
Steelies Posted November 18, 2012 Share Posted November 18, 2012 eepiiiiiic! hmx haha, take that cool markku, glad we'll see you competing at the next dromageddon. Quote Link to comment Share on other sites More sharing options...
sentra Posted November 18, 2012 Share Posted November 18, 2012 Ned so your saying if he ran all the same sized pullies to me he would be running at the same speed as me, with his 16 inch wheels? unless i be reading this wrong, then yes on twin rim, 1 inch of belt travel = 1 inch of bike travel, regardless of dia, it only matters when your running it like sam & pete Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 18, 2012 Share Posted November 18, 2012 realy. honestly dave. maybe if he was running no tyre Quote Link to comment Share on other sites More sharing options...
sentra Posted November 18, 2012 Share Posted November 18, 2012 compared to the change per mm of the front pulley its neligible auuu Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 18, 2012 Share Posted November 18, 2012 yesfront pully makes way more difference. but also the inner diameter of the rim that the belt runs on wont be the same on er wheel. like on my bike I used two different rims and where my belt runs is lower than the id of the rim the tyre is on. you gota measure circumference/ work out diameter of what the belt is driving. and the diameter of your wheel + tyre Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted November 18, 2012 Share Posted November 18, 2012 You kids and your belts. Good ol cogs N chains is where its at. Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 18, 2012 Share Posted November 18, 2012 ima put heaps of chains on my kirk mk5. almost worn out the belt on my bike doing burnouts on Saturday lol. gota chop the frame to get it out to replace ahha. shit Quote Link to comment Share on other sites More sharing options...
Testament Posted November 18, 2012 Share Posted November 18, 2012 It's close as although the wheel is smaller, the drive pulley is smaller too (assuming rim drive) there is a difference as the ratio of the tyre OD to rim ID is greater as the rims gets smaller and the tyre "thickness" stays similar regardless of diameter. that said ned is right in that its only a small difference compared to the overall reduction neccesary, of something between about 5:1 and 8:1 depending on engine rpms, wheel size and target speed Quote Link to comment Share on other sites More sharing options...
Seedy Al Posted November 18, 2012 Share Posted November 18, 2012 so he could go bigger. Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 18, 2012 Share Posted November 18, 2012 Hah, ok. Going by those calks I'll only need around 5:1 reduction for 80kph, which should be pretty easy. That means 1:1 to the lay shaft and a 60mm pulley to drive the rim (should be 305mm to the inside of the rim, but haven't measured). yeh sounds right my bike is 5.8:1 including reduction from tyre size. which = bowt 80 at 5000. that's a good ratio. my bike lacks the talks down low but anything that's not a 100cc 2t will be fine with that ratio lol. edit and yeh my front pully is about 67mm I think. I would like to go down to 60-ish Quote Link to comment Share on other sites More sharing options...
Ned Posted November 18, 2012 Share Posted November 18, 2012 so he could go bigger. no, he actually wants to go smaller with a smaller wheel to get the same speed as you because the rear wheel pulley setup is a reverse reduction and the smaller the wheel, the bigger percentage change it will have on the overall ratio. It really isn't very big, hence why most dismiss it to get something going. but; On a 20" wheel with a 1.5" tall tire, vs 16" wheel with a 1.5" tall tire, the difference is ~10km/h at 5000 rpm. I'd go for a 60-65mm diameter pulley to get to 80-90km/h on your bike. Maybe even smaller and get some valve springs so you've got more power for drag racing etc a 50mm pulley will still get you to 100km/h at 7000 RPM whereas a 60-65mm one will get you to 120-130 at 7000rpm *disclaimer, this is all coming from a spreadsheet i made and even though i'm fairly sure it's correct, i could quite easily be wrong sorry.... Have a look if you wanna check it ou/calculate shit. http://dl.dropbox.com/u/39307891/Bike%20Speed%20Calculator%202.xlsx Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 18, 2012 Share Posted November 18, 2012 ^yeh ned your maths is right cos my bike is running the same setup(sizes/ratio) and reality has = the same as maths equations theory speeds Quote Link to comment Share on other sites More sharing options...
Rookie Posted November 18, 2012 Share Posted November 18, 2012 This is exactly how we worked it out for our bikes, and every one has been wrong. So best bet is to just wing it. Quote Link to comment Share on other sites More sharing options...
Seedy Al Posted November 18, 2012 Share Posted November 18, 2012 So best bet is to just wing it. Do you mean a Propeller? Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 18, 2012 Share Posted November 18, 2012 http://jimsitton.net/ratiocalc/ right click, download the gearratio.exe thing. does up to like 5 layshafts and has metric aswel as imperial and works on either pully diameter or sprocket tooth count. does friction drive aswel. workd out like 95% accurate on my 3 bikes I used it on. I guess aerodynamics and driveline loss is the difference Quote Link to comment Share on other sites More sharing options...
Testament Posted November 19, 2012 Share Posted November 19, 2012 I never calculated because we only had the two pulleys and one was always going to be too big. the main problem is guessing at what rpm the engine is going to pull with most of these random industrial/ag motors Quote Link to comment Share on other sites More sharing options...
Seedy Al Posted November 19, 2012 Share Posted November 19, 2012 yeah Kicker just purchased A Laser tachometer. Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted November 19, 2012 Share Posted November 19, 2012 ^ Yeh, you can get them super cheap from china, you just stick a bit of reflective tape on and point it at it, and whamo, RPM's. Quote Link to comment Share on other sites More sharing options...
KIRK Posted November 19, 2012 Share Posted November 19, 2012 I need to buy one. I usualy use the one at lawnmower shop that you touch onto the sparkplug boot. Quote Link to comment Share on other sites More sharing options...
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