Sprocket size and top speed

[iwasgandhi]

Background info before my question:
I have a Staton-inc axle mounted gas kit on a 26" wheel bicycle. My current top speed is 28mph, using a 13 tooth small sprocket and a 60 tooth large sprocket. I can adjust my top speed by changing the size (the number of teeth) of one or both sprockets. However, I'm not satisfied with the variety of large sprockets for sale on Staton-inc.com, because I can't dial in my top speed more precisely. Therefore, I want to purchase a custom-made large sprocket from www.electricscooterparts.com, so as to better dial in my top speed closer to 30mph.

Question: what is the mathematical formula (or ratio) for calculating the top speed of my Staton-inc axle kit, given that the only two variables in the equation (or ratio) are the number of teeth on the large and small sprockets?

I can order a custom-made large sprocket from www.electricscooterparts.com with the exact number of teeth that I specify. For example, the large sprocket can have 53 teeth or 47 teeth -- whatever number I specify.

I want my top speed to be as close as possible to 30mph, yet without going over 30mph. My ideal top speed would be precisely 30.0mph, but somewhere between 29.5mph - 30.0mph would be acceptable.

I hope to use an 11 tooth small sprocket, which I've already purchased from www.staton-inc.com, along with a custom-made large sprocket.

Thanks.

 

[5-7HEAVEN]

With a 13t/60t, a Staton 4.28:1 gearbox and 26" tires, your present ratio would be 19.75:1.

At 7,150rpm, speed is 28mph.

Changing to a 14t/60t, ratio would be 18:32, with speed of 30mph at 7125rpm.

Using an 11t, you'd need a 48t sprocket to have a ratio of 18.33:1 and 30mph, at 7250rpm.

So the cheapest solution is to swap to a 14t.

You won't even notice a 25rpm loss at that speed,
but it'll take you longer to get up there.

Lol, all this for a 2mph increase.
But the engine should run with less strain,
unless you're a heavy guy and ride on hills.

For the formula, research "jimsitton calculator" on the forums.

 

[iwasgandhi]

With a 13t/60t, a Staton 4.28:1 gearbox and 26" tires, your present ratio would be 19.75:1.

At 7,150rpm, speed is 28mph.

Changing to a 14t/60t, ratio would be 18:32, with speed of 30mph at 7125rpm.

Using an 11t, you'd need a 48t sprocket to have a ratio of 18.33:1 and 30mph, at 7250rpm.

So the cheapest solution is to swap to a 14t.

You won't even notice a 25rpm loss at that speed,
but it'll take you longer to get up there.

Lol, all this for a 2mph increase.
But the engine should run with less strain,
unless you're a heavy guy and ride on hills.

For the formula, research "jimsitton calculator" on the forums.

Thanks for the info. Unfortunately, I don't have enough room on my cheap smartphone to access the jimsiiton calculator file. And, as I don't have an internet computer, just a dusty 1985-ish Macintosh, I'll check out the "j-calc" on a public internet computer at a public library.

My general budget is tight and, more specifically, my gas-bike project is on a shoe-string budget, hence my use of a cheap smartphone and my lack of a laptop, etc.

www.staton-inc.com lists the top speeds when using various small sprockets on an axle mounted kit (4.28/1 gear reduction box) -- when also using a 60t large sprocket and a 26" wheel.
According to Staton:
10t/60t/26" = 22.0mph
11t/60t/26" = 24.5 mph
12t/60t/26" = 25.9mph
13t/60t/26" = 28.0mph
14t/60t/26" = 31.5mph
15t/60t/26" = 35.0mph

Perhaps the jimsitton calculator is more accurate than Staton's list.

I'm a heavy guy (260 lbs, 5'10") and there are some long, steep hills in my area. I'm also a heart attack survivor who needs to keep my max. heart rate around 150bpm, so I need an engine with enough torque to enable me to motor-pedal up the hills in my local area without overly stressing my heart.

For a couple years I used a Honda GX35 (35cc) 4-stroke on my Staton-inc axle mounted kit, but I found that 1.6hp didn't cut it. I ended up lugging the poor lil' the engine, despite peddling uphill to assist the engine, and I went through two GX35 engines in approx 2 years. Each one ended up getting "blow-by", whereby gas contaminated the oil reservoir. Oil also seeped from the cooling fins. T'was unsightly.

Before the two Honda GX35's, I used a Robin-Subaru 35cc. It lasted approx. 8 months. It, too, ended up getting "blow-by", and oil also seeped from the cooling fins.

I changed the oil regularly on all three 4-strokes, so I figure my weight must've been too much for a 35cc 1.6hp 4-stroke.

When using the above three engines on my Staton-inc axle mounted kit (w/26" wheel), the best combination of sprockets, given my weight and the hills in my local area, was 11t/60t, for a top speed of only 24.5mph. Not fast, I know, but it got me up most of the hills. Occasionally I had to hop off and push my steed up a long, steep hill.

For my current project, I'm tentatively planning on using a Honda GX50 (50cc 4-stroke w/2.0hp) on my Staton axle mounted kit. I want my ride to be 100% road legal in New Hampshire, so that's why I'm concerned about hp (2.0hp or less), as well as top speed (30mph or less). If I can do better than 28mph (13t/60t), then I want to do so, because every mph faster equates to better mpg, which means money saved.

Every mph counts because every penny counts, especially on approx. $800/mo. However, it's a careful balance between torque, top speed, and legal requirements in NH. That's why I'm seeking the best combination of sprockets for my specific circumstances.

I went through the process of getting a VIN issued by the NH State Police, as well as getting an actual moped plate. In the past, I also had liability insurance coverage from Allstate, plus roadside coverage from Allstate. Roadside came in real handy in Sept., 2014. A flat bed hauled my ride approx. 70 miles.

Lots of guys on happy-time kitsch say "someone told me it doesn't need to be registered as long as it's under 50cc". They speak with confidence and truly believe what they've been told -- whomever told them. But they're just plain wrong. I've heard it so many times.

The impression I get is that most of these guys (not all but most) have lost their driver's licenses due to driving under the influence. Some have outright admitted to me as much. Others are suddenly and completely disinterested when I matter-of-factly explain NH's registration requirements for gasoline powered vehicles on public roads.

I don't judge other guys on gas bikes if they've struggled with addiction, just as I have, and they're now doing their best to get their lives back on track. It takes courage to face one's problems and to get help to recover. What I don't like are the guys riding unregistered gas bikes here in NH, and who are still fooling themselves and others, still living a lie -- the guys who couldn't care less about NH's legal requirements, because they prefer to keep riding illegally, thus making the rest of us look bad.

It takes what it takes, I guess. Everyone's on a different timetable.

By the grace of my HP, I stay clean & sober, and I get moderate exercise in other ways, so I figure my gas bike is a justified expense, because it enables me to travel cheaply (150+ mpg) spring, summer, and fall -- far more cheaply than when driving my '99 Saturn SL2 (30mpg av.).

One drawback to my Staton-inc kit is the poor customer service from Staton. Sometimes he doesn't reply to short, succinct emails, and sometimes I've purchased an item but it was never delivered. It then took literally months to get a refund.

However, I like the axle mounted kit because there's no obstruction from the engine when pedaling with the kit installed (no engine in the triangular frame), there's no high speed chain next my left leg, it's easy to remove the kit when I want to return to a pedaling-only bike, and it allows me to mount a milk crate on a rack above the rear wheel, plus I can carry a saddle bag on the rear rack (kit on left side of rear wheel, saddle bag on right side of rear wheel).

Sorry this is so long. Had some free time this evening.

 

[5-7HEAVEN]

If you’re heavy and have hills to climb, I wouldn’t change gears.

Going to higher gears for better mpg will reduce your low end power and torque.

If you’ve burned out 3 engines, something is seriously wrong with your setup.

You could be lugging your engines, or overrevving them.

I don’t know, but you’d know.


With your weight and hills, I’d keep the 13t or drop down to 11t.

And keep your speeds low.

Don’t shoot for 30mph.

 

[5-7HEAVEN]

I’ve had issues with Staton too.

I have a thread on it here.

Exactly like you.

When I mentioned Better Business Bureau, Staton emailed promptly and sent my refund.

 

[iwasgandhi]

If you’re heavy and have hills to climb, I wouldn’t change gears.

Going to higher gears for better mpg will reduce your low end power and torque.

If you’ve burned out 3 engines, something is seriously wrong with your setup.

You could be lugging your engines, or overrevving them.

I don’t know, but you’d know.


With your weight and hills, I’d keep the 13t or drop down to 11t.

And keep your speeds low.

Don’t shoot for 30mph.

I never thought of over-revving as being a possible cause of the blow-by problem. I'm not a mechanic, just someone who knows how to assemble a Staton axle mounted kit and ride for fun. And I never used a tachometer with my ride, so I don't know what my rpms actually were. I honestly have no idea what caused the blow-by problem. I wondered if maybe it was E10 gas -- without any ethanol treatment additive. It's the only gas in my area (there's no ethanol-free gas for sale in my corner of NH, as far as I know). Also, I used only 87 octane in all three 4-strokes. Not sure if that did it. Maybe I should have used the highest octane? As far as changing the sprockets and aiming for a 30mph top speed, I would only do so if I use a more powerful engine than the 1.6hp 4-strokes I've used in the past. In the future might use a Honda GX50 (50cc) 2.0hp 4-stroke, or possibly a Tanaka PF-4000 (40cc) 2.2hp 2-stroke. Not sure yet which engine I'll end up using. It's tempting to try yet another Honda GX35 (35cc) 1.6hp 4-stroke, as it's good on gas and very quiet, but I'd first want to figure out what caused the blow-by in my three previous 35cc 4-strokes. If I can avoid getting the blow-by problem yet again, I'd use another Honda GX35 (35cc) 1.6hp 4-stroke with an 11t/60t sprocket setup like before (26" wheel), for a top speed of 24.5mph

 

[Chainlube]

I never thought of over-revving as being a possible cause of the blow-by problem. I'm not a mechanic, just someone who knows how to assemble a Staton axle mounted kit and ride for fun. And I never used a tachometer with my ride, so I don't know what my rpms actually were. I honestly have no idea what caused the blow-by problem. I wondered if maybe it was E10 gas -- without any ethanol treatment additive. It's the only gas in my area (there's no ethanol-free gas for sale in my corner of NH, as far as I know). Also, I used only 87 octane in all three 4-strokes. Not sure if that did it. Maybe I should have used the highest octane?

Ethanol gas will gum up a carb, but you can remove the ethanol easy at home, no treatment needed.

 

[iwasgandhi]

Ethanol gas will gum up a carb, but you can remove the ethanol easy at home, no treatment needed.

Thanks. I appreciate the info and the video . The method shown in this video would be practical only if I'm traveling within the range of one gallon (or so) of gas that I'd prepare ahead of time and carry with me on my ride. But if I ever needed to go the distance, such as traveling over 200 miles interstate, as I've done before, then I'd need to use an ethanol treatment on the road -- at the pump. So I'm planning on using STA-BIL-360 ethanol treatment for my longer trips. But for my shorter trips I'd like to experiment with the method outlined in the video.

 

[Chainlube]

You also must be aware that ethanol adds octane to the gas too, so an octane booster might be required.

 

[iwasgandhi]

You also must be aware that ethanol adds octane to the gas too, so an octane booster might be required.

Thanks. Do you know how much octane booster would be required?