I am thinking of a 6.5hp rear drive.

[bike4life]

This do 50mph yet???

Well it’s done. I tested it out today. Rode in 20miles. I’ll take a yt video tommorow

 

[bike4life]

Heres the thing. Currently with the 4 stroke 6.5hp, it tops out at only a tiny tiny 16mph with a 10” wheel and a torque converter at max throttle where the gear ratio from the converter to the wheel is 10:25t. I don’t understand. I’m not sure if the engine is spinning to its full3600rpm. Governor isn’t removed. So I road 20mi to harborfreight and bought a laser tachometer for 30 dollars to get measurements. My plan is then to decrease the sprocket size. Yikes, what should I do. I officially started on March 18, but didn’t work on it really all summer, so that’s about 4 or 5 months. I’m slow but hey, the government is even slower.

 

[CrazyDan]

Is that a toy hardhat?? Please get better protection.. I'd rather not help you get a higher top speed, would feel bad if you wrecked bad at high speed. But if you insist, a larger front sprocket or smaller rear would increase speed. A larger tire on the pusher would also increase speed.

 

[bike4life]

Is that a toy hardhat?? Please get better protection.. I'd rather not help you get a higher top speed, would feel bad if you wrecked bad at high speed. But if you insist, a larger front sprocket or smaller rear would increase speed. A larger tire on the pusher would also increase speed.

I already knew that will increase speed since like forever, its simple, so no worries about that. I was wanting to get your thoughts on the math calculations which seemed to contradict that of the real world testing. Therefore, i think using a tachometer is a good idea to quantify these values because something doesn't add up or make sense..... Ill post the values from the tach tommorow.

 

[digital_life]

https://motoredbikes.com/attachments/046d61a1-47e7-4f64-b83b-71a167570549-jpeg.90501/
Well it’s done. I tested it out today. Rode in 20miles. I’ll take a yt video tommorow

I hope that sign on the top of the motor wasent from the edge of a cliff

 

[FNTPuck]

Heres the thing. Currently with the 4 stroke 6.5hp, it tops out at only a tiny tiny 16mph with a 10” wheel and a torque converter at max throttle where the gear ratio from the converter to the wheel is 10:25t. I don’t understand. I’m not sure if the engine is spinning to its full3600rpm. Governor isn’t removed. So I road 20mi to harborfreight and bought a laser tachometer for 30 dollars to get measurements. My plan is then to decrease the sprocket size. Yikes, what should I do. I officially started on March 18, but didn’t work on it really all summer, so that’s about 4 or 5 months. I’m slow but hey, the government is even slower.

I already knew that will increase speed since like forever, its simple, so no worries about that. I was wanting to get your thoughts on the math calculations which seemed to contradict that of the real world testing. Therefore, i think using a tachometer is a good idea to quantify these values because something doesn't add up or make sense..... Ill post the values from the tach tommorow.

I told you the proper math calculations months ago but you refused to listen.

Its simple...RPM, gearing, wheel diameter...but going too far to the extreme on either of those(too small sprocket, too large wheel, etc) and you will have issues. You don't have the RPM or the wheel diameter(mostly wheel diameter) to go anywhere near 50mph on a stock 212, and under gearing it to try to cheat your way there just makes it so that your motor won't have the strength to accelerate after a certain speed (AKA you won't have enough power to to rev all the way out). TQ converter final drive is nearly 1:1 (some 30 series have 10% overdrive so actually a bit more) at full speed and has ~3:1 reduction off idle to help low end. That means you just use your crank sprocket size, rear sprocket, and wheel OD x RPM to get final speed. Your 10:25 gearing on a 10" tire may THEORETICALLY get you ~40mph, but with only a 2.5 ratio it doesn't have enough TQ to ever actually get there so is falling on its face around 2000rpm. Most 212s aim for between 6-9 gearing ratio and you are not even at 3. The only reason you can even get it moving is because the TQ converter adds a ton of low end TQ which allows a smaller rear sprocket while maintaining low end...if that was with a clutch and 10:25 gearing you would just smoke the clutch. If the only thing you have to think about was the sprocket size, everyone would just buy $90 ebay chinagirls with a 28t rear sprocket and go 70mph...you need the TQ to pull that gear and with chinagirls, a 32t rear sprocket is SLOWER on a stock motor than a 36t since it doesn't have the power to pull the lower gearing. That's also why the weak old 66cc motors came with 44t and newer triple40s come with 36t.

For your build, first thing you need is to get a tach on it and verify the rpms. Then, get a LARGER 44t sprocket and some 20" BMX wheels. You will do almost 50mph and likely end up in a hospital, but you will reach your goal.

Note that I still think you need to just gear it for 30mph tops with trailer brake to stop you to even be close to feasible and safe for a daily rider (I would just weld a disc on the rear axle and do a cheap mechanical disc brake on it).

 

[bike4life]

Hey FTPNKPUCK. I dont understand a few things but kinda know what your are saying. First off, bakenos ebike got 50mph on like 3000watts of power was drawn to acheive that. The 212cc is used in 4000watt generators. So power = torque * rpm / 5252. My Engine should theoretically have enough power to achieve that speed. The next question is what is the required rpm's and torque to achieve it.

A 44t sprocket on a 20" tire is EQUIVALENT to a 22t sprocket on a 10" tire. They cancel out. Its like an equation. You divide both sides by 2, its still equal. My sprocket is a 25t, so its has around 10% more torque and 10% less rpms that a 44t and a 20" tire.

With the tachometer, i was getting like 1300 ish rpms with the trailer off the ground, which would theoretically yeild 40mph. I don't understand why when i put it on the ground, it dropped to 20mph. It seems like their was not enough torque or something is weird with the converter, idk as it must have went slower. So today, i just removed the whole wheel assembly and bearings and now ordered a 10t sprocket as an experiment.

I need to use a tire with a 5/8" shaft so it can fit on my apparatus with the pillow blocks and such. I am not sure a bmx tire accepts a 5/8 shaft, so i am for now keeping my 10" tire, unless you can explain how a 44t sprocket on a 20" tire isnt equal to a 22t on a 10in tire.

 

[FNTPuck]

Hey FTPNKPUCK. I dont understand a few things but kinda know what your are saying. First off, bakenos ebike got 50mph on like 3000watts of power was drawn to acheive that. The 212cc is used in 4000watt generators. So power = torque * rpm / 5252. My Engine should theoretically have enough power to achieve that speed. The next question is what is the required rpm's and torque to achieve it.

A 44t sprocket on a 20" tire is EQUIVALENT to a 22t sprocket on a 10" tire. They cancel out. Its like an equation. You divide both sides by 2, its still equal. My sprocket is a 25t, so its has around 10% more torque and 10% less rpms that a 44t and a 20" tire.

With the tachometer, i was getting like 1300 ish rpms with the trailer off the ground, which would theoretically yeild 40mph. I don't understand why when i put it on the ground, it dropped to 20mph. It seems like their was not enough torque or something is weird with the converter, idk as it must have went slower. So today, i just removed the whole wheel assembly and bearings and now ordered a 10t sprocket as an experiment.

I need to use a tire with a 5/8" shaft so it can fit on my apparatus with the pillow blocks and such. I am not sure a bmx tire accepts a 5/8 shaft, so i am for now keeping my 10" tire, unless you can explain how a 44t sprocket on a 20" tire isnt equal to a 22t on a 10in tire.

Not going through your math but 1300rpm on a 10" tire with 10:25 gearing is almost exactly 16mph. Not 40mph.

Again, you are doing something way wrong and I don't have the time to go through it all to find out what...just use a gearing calculator man.

There is not enough TQ because your gearing ratio once the converter starts adjusting is terrible.

 

[bike4life]

Not going through your math but 1300rpm on a 10" tire with 10:25 gearing is almost exactly 16mph. Not 40mph.

Again, you are doing something way wrong and I don't have the time to go through it all to find out what...just use a gearing calculator man.

There is not enough TQ because your gearing ratio once the converter starts adjusting is terrible.

what is the ideal gear ratio for a converter...

 

[FNTPuck]

1300rpm is waaayyy too low for a 212. Stock governor should allow 3600rpm with no load.