Just remembered that your chainring is sent through a multiplication too so if you have a 36t front chainring and an 18 driven when you spin 120 its spinning 240 so that'll help and you probably have more like a forty something 48 would make 360 and be perfect for pedal assist!
Another Harbor Freight Attempt
- Thread starter MaxPower
- Start date
Attached are some photos of a Max-Torque 5mm HTD Clutch set up for the Honda GXH50 and a couple of Pfeifer Industries 5mm HTD Driven Pulleys. The Pfeifer Pulleys are aluminum and when you buy them they are 40mm wide and will need to be trimmed to the width of the belt you are planing to use. The second photo shows a 40mm wide pulley in the lathe being trimmed to its finished width for a 25mm belt.
You will note that the Pulleys are are not a solid thickness through out They are actually quite light. As for costs the MaxTorque Clutch I believe was $88.00 and with shipping just under $100.00. The two Pulleys from Pfeifer were if I remember correctly were $40.00 each I was able to combine them with the shipping on the clutch as Max Torque and Pfeifer are located next door to each other and they are owned by farther and son.
ocscully
You will note that the Pulleys are are not a solid thickness through out They are actually quite light. As for costs the MaxTorque Clutch I believe was $88.00 and with shipping just under $100.00. The two Pulleys from Pfeifer were if I remember correctly were $40.00 each I was able to combine them with the shipping on the clutch as Max Torque and Pfeifer are located next door to each other and they are owned by farther and son.
ocscully
Attachments
got another reply from Max-Torque.
I sent him the drawing of the shaft in the operating manual and asked if the HTD clutch would fit on it.
James F. Donovan
"You are putting the engine on your bike. What I would suggest is you build a sturdy jackshaft and mount the clutch on that. Go from the crankshaft to the jackshaft with a chain of timing belt and reduce the speed of the engine 2:1 reduction -- when the engine is going 4,200rpm then the jackshaft is going 2,100.
Why --because it is a high rev engine and idles damn high -- 2,700 to 2,800. Also you would have to mount the clutch outboard with the pulley at the end of the crankshaft which is now relying 100% on the bolt and washer to support the tension on the clutch. You are asking a heck of a lot from a M8 bolt. Truth is the bolt will fail at the worst time-- when you are on the bike a long way from your shop.
The crankshaft is too short to fully support a clutch. I have modify some clutch to accept a chain and it will work but a timing belt is a different story. You must run a timing belt tight and it should have a roller bearing in it not a bushing because of the tension that is constantly on it. If we had the standard 2.300 long crankshaft it would be easy but with the stub crankshaft you must plan around it."
tyrslider: what modification did you make to the max-torque clutch on your gearbox? Can I just plug and play withe the HTD clutch?
I sent him the drawing of the shaft in the operating manual and asked if the HTD clutch would fit on it.
James F. Donovan
"You are putting the engine on your bike. What I would suggest is you build a sturdy jackshaft and mount the clutch on that. Go from the crankshaft to the jackshaft with a chain of timing belt and reduce the speed of the engine 2:1 reduction -- when the engine is going 4,200rpm then the jackshaft is going 2,100.
Why --because it is a high rev engine and idles damn high -- 2,700 to 2,800. Also you would have to mount the clutch outboard with the pulley at the end of the crankshaft which is now relying 100% on the bolt and washer to support the tension on the clutch. You are asking a heck of a lot from a M8 bolt. Truth is the bolt will fail at the worst time-- when you are on the bike a long way from your shop.
The crankshaft is too short to fully support a clutch. I have modify some clutch to accept a chain and it will work but a timing belt is a different story. You must run a timing belt tight and it should have a roller bearing in it not a bushing because of the tension that is constantly on it. If we had the standard 2.300 long crankshaft it would be easy but with the stub crankshaft you must plan around it."
tyrslider: what modification did you make to the max-torque clutch on your gearbox? Can I just plug and play withe the HTD clutch?
He's confusing this motor w/ the honda. This Motor idles at around 1200. you should be able to plug and play. The clutch extends out about a 1/4" past the end of the shaft and the bolt that retains it is only holding it on the shaft it is not being stressed or pulled on. There's no tendancy for the motor to pull it off. In fact if you think about it it would have to pull the pulley off too. also you will not have to have it out as far if you don't have a trans. back plate to clear.
Maybe I'm confused here but I thought the HF Greyhound was a low 3600 max rpm motor? Am I wrong in thinking this? I didn't see any rpm specs in the owners manual at the HF web sight. Aren't these motors clones of the Honda GX160 and GX200? I realize that the 2.5hp motor is only 79cc. In the first photo of my previous post you can see the special shaft extender piece that is necessary to fit the HTD clutch to the short 1 1/4 in. Honda crankshaft. Two years ago when I purchased my HTD clutch Jim had reservations about how I was planning to use it and he recommended the same set up (putting the clutch on the jackshaft with a 2:1 reduction) But I couldn't get the overall reduction that I needed with just 2:1 as the primary reduction. The spec. I saw in the HF manual indicates that the 5/8 portion of its shaft is 50.5mm (almost 2 in.) Trysliders posts seem to indicate the the HF motor must idle around 1000 rpm - 1200 rpm ?
ocscully
ocscully
So I'm about ready to order parts and get this thing built but I'm still up in the air about the pulley size. I'm confident that I'll use the max torque HTD, and a Pfeifer pulley and belt (v-belt and chain out). I'm still afraid to ask what they won't for a 11" pulley. It might ruin my whole project. I hope its the same price as ocscully's pulleys. tyrslider thinks I need a 9" (1.5" to 9" is 6:1). But I'm thinking that will be too low. my original thought was for a 12" for a high ratio. I was a little confused with MotorbikeMike's suggestions but he seems to know whats going on. Is there a way to figure this out using physics? I mean crunch engine performance data with weight, torque, friction loss, engine efficiency, belt slippage, rotational acceleration and all that other jargon? I'd really like to be sure this is a good idea before flopping down $500.
I will need a belt about 6ft long. Is this a good idea? I have no experience with belts. to much stretch?
tyrslider, I assume your mount is universal and can fit my frame. my seat tube is 1.25" and down tube is 1.5". What is an estimate on engine dimensions with your mount? I recall you said 8.5 by 11. also did you use wider cranks on your bike? I'm not sure if I can mount the engine high enough. Will wide cranks clear the engine if mounted low?
I will need a belt about 6ft long. Is this a good idea? I have no experience with belts. to much stretch?
tyrslider, I assume your mount is universal and can fit my frame. my seat tube is 1.25" and down tube is 1.5". What is an estimate on engine dimensions with your mount? I recall you said 8.5 by 11. also did you use wider cranks on your bike? I'm not sure if I can mount the engine high enough. Will wide cranks clear the engine if mounted low?
Last edited:
I think your complicating things a bit. The ratios I discussed will work. 6:1 Primary w/ a 10 tooth drive to the rear freewheel. But if you run a 1.5"/11" or 7.333:1 and an 18t rear on a 26x2.125 tyre you'll be going like 37mph in middle gear w/ a similar SRAM freewheel (couldn't find yours in the calculator). you need to go smaller on the rear drive like a twelve would put you at 30ish in middle gear. Also you need to find an accurate belt calculator and see if that length is ok. Is it available that long and can it take the rpms at that length are good ?'s to start w/. Good luck I'm pullin' for ya!
18t is as small as i can go on the jackshaft output. the chain stays will interfere when I go to the 14t sprocket on the cassett
When you use that timing belt I think you will want to use the # of teeth not diamiter to figur out ratio. So the Max torque htd is 23t the pulley they have is 176, thats 176/23 or 7.652/1 ratio. multiply that by .78 and 1.78 and you have 5.970/1 and 13.621/1. By my calculations your top speed 4500 rpms is 57.389 mph and 25.153 mph. I think that might be a little too fast.
Looking at the pic I believe he only listed hi/lo on a 7 speed cog (I could be wrong). Your calculations sound right.
I just used the sheldon brown gear calc and an SRAM 7 speed cog w/ similar gearing.
BTW does not matter whether you use teeth or diameter in ratio calculations; it's the same.
I just used the sheldon brown gear calc and an SRAM 7 speed cog w/ similar gearing.
BTW does not matter whether you use teeth or diameter in ratio calculations; it's the same.
Yeah I got to looking at the difference in our numbers and they are really close.
I round #'s a little too so they're close but not exact.
Your engagement speeds sound right, you can slip it a little too.
ocscully where did you get that shaft extension? The only thing I can find is this shaft. To use the shaft I found you would have to drill the engine shaft with a 5/16 bit and re-tap it to 3/8-16. After that you would probably want to cut the extension down to about an inch.
Felton,
The shaft extension came with the Max Torque HTD clutch when I purchased it. Jim at max Torque might still have them but I'm not sure? Back when I bought my clutch, Max Torque had just recently made a batch of clutches for a client who was making some type of Robot that was powered by a GXH50 motor. When I contacted Jim about a clutch for my bike project he sold me one of the special clutches he had left over from the robot project.
ocscully
The shaft extension came with the Max Torque HTD clutch when I purchased it. Jim at max Torque might still have them but I'm not sure? Back when I bought my clutch, Max Torque had just recently made a batch of clutches for a client who was making some type of Robot that was powered by a GXH50 motor. When I contacted Jim about a clutch for my bike project he sold me one of the special clutches he had left over from the robot project.
ocscully