Mountain Bike Conversion 24v 3/4hp
This blog is a work in progress, an evolution in design you might say. As you migrate through the Parts (Chapters, if you will), please note that the blog follows my process of thought, design, failure, re-design, more thought, refinement or even different design etc. Hopefully, all the way to success.
(For example, I had some ideas for how to place the batteries, I tried one way, it became obvious that it wasn't going to achieve my goals, I tried another way and it still didn't seem right. Eventually, it came together in such a way that I now feel confident that it will work well.) This is true of various aspects of this project and things may change and change again.
I tell you this because it's important to not get too disappointed when approaching a project like this, not give up the ship. It may not be easy but you will find a way and it will take mistakes to get there.
(I'll be working on making the blog better too, in time.)
I'd like to introduce myself.
I'm Dave and I live in Carson, WA.
Carson is located in the beautiful, Columbia River Gorge at the foothills of the Cascade Mountain Range in the Pacific Northwest. Much of the terrain here is rather steep and there are many abandoned back roads to traverse here. I also want to use the bike for local errands.
I've got a 1985 Bridgestone MB-1 which I am in the process of converting to a Pedal Assist Electric Mountain Bike.
Since the bike is a vintage model, any conversion that I do will not make any permanent changes to the bike.
Motor: Scott 3/4hp, 560W, 24VDC (3000 RPM)
Controller: Alltrax AXE4824 (Upgraded from a Navitas 100-36)
Throttle: 0-5k Twist Grip
Batteries: 8ea 12V-9Ah (36Ah total at 24V)
Reduction: Belt/ Chain 12:1 (total reduction)
Jackshaft: Converts Belt to Chain Drive w/ Freewheel
Charger: Iota 15A 12V w/ IQ4 3-stage circuit
Top Speed - 20mph
Range - 20 miles (at reduced speed, level ground)
Ability to traverse some rather steep inclines as needed
Charge batteries using my Wind Generator and Solar Panels. (Wind ~ 50W/ Solar ~ 37W)
So far, I've tuned up the bike. Put in new bearings, disassembled, cleaned, reassembled and adjusted every mechanism on the bike.
I have the Scott 24V motor, a "Doc Watson" digital DC ammeter, amp hour meter and just ordered the 100 Amp Controller. I also just placed an order for the batteries and the twist grip throttle.
I found a guy on eBay that makes jackshafts for go-karts and sent him some plans for what I need.
The real challenges will be securely and strategically placing the 8 batteries and attaching the 60 tooth #35 chain sprocket to the left side of the rear wheel (without compromising the bike).
I plan on sandwiching the spokes between the 60T sprocket and a split ring with some neoprene (inner tube) gaskets. I'll probably have some spacers at each bolt.
As for the batteries, I plan on placing 6 of them within the frame opening below the horizontal bar and two more below the frame. To hold them in place, I'm making an acrylic frame (trianguar box) and will use expanding foam to secure the batteries within that.
I'll post some pics of the e-bike in progress and after as I work on it.
(I haven't posted pics here before, so I'm not sure what size works best, I appologize if these are too big)
Wish me luck!
This is the MB-1
spookytooth cycles in arizona has a rear sprocket attachment. I used the stanton hub from stanton inc for my bike. Did you read Eric Peltzer, google it up. I designed a jackshaft in cad, will see if I can post it. Never made the jackshaft.
I used the gates pg2 belt5mr700-15 belt and the 21 tooth motor sprocket and 64 tooth jackshaft sprocket. for the final drive the wheel sprocket is 45 tooth. final ratio was "i think" about 10 to 1. I tried 9 to 1. My new bike
comment on building this. I looked at your drawing. I built version one about the same, motor directly above the rear axle. This was a mistake, the bike flexed to much, put the motor as close to the seat as possible. I used maxxis hookworm 2 1/2" 26" rims. If you use 11 to 1 gearing you should power up hills. I don't know how to properly post pictures here, also, for some reason, on this website, my keyboard dies so I can rarely finish a reply.
My final version using the scott 1 hp motor, 24 volt, 56 lbs of battery, 4 oddysey pc 625 batteries, maxxis tires from above, 10.4 to 1 gearing. On the flat, 25.5 mph. On good grades 5 to 10%, 22.5 mph,, downhills 27 mph. bike weighs about 100 lbs, I way 215 lbs. Riding the bike as hard as I can, fast starts, many hard stops, up and down hills and with a 30 mph headwind, 15 mile range at top speed. ps, also using an alltrax 180 amp controller
If i had to build this again, i would build it just like Eric's. Why, chain adjustment, if you look at my rack at the axle the threads for the adjuster are visible. The chain for the 1st hundred miles stretched a lot. But, one full turn of the adjuster was too much. If you go with a rack, which sounds easier, make sure chain tension can be easily adjusted. A quarter turn will take up a 1/4" of chain slack. I own a welding shop, metal saws, drill presses, end mill, mig and arc welders, vises. And yet, it took me probably 20 hrs to build the rack, then, probably that much or more time modifying.
Truly, it would have been easier to build Eric's design, I lived and learned.
It took me 48 hrs to build my second bike, I purchased John Bidwells book the Cheetah, in Texas I don't have to have pedals so its still legal as a bike to 20 mph. The rack as simple as it seems, was extremely difficult to build. Clearances, chain, pillow block bolts, motor mount bolts, a 1/16" clearance here there and every where, all parts where in the way of other parts, very frustrating.
I did'nt Build it like Eric's because I do not own a metal lathe to make the jack shaft.
When I moved the motor under the seat, my seat was a tad too high for comfort, all the weight was too high, but, it eliminated the torsion flex, which was severe when the motor was about 5" farther back. Putting the motor low like Erics would have been ideal on my set up.
The original bike, the raleigh, is a chrome moly frame. Very strong. No suspension. At speed, say 20 to 25 mph, I could not track in a straight line. I always got a little knot in my stomach riding. Then, I put a cheap rst suspension fork on the bike. Even though the fork always bottomed out, my tracking became very good, much more comfortable. The pc 625 oddysey batteries are 18 amp hour. This bike had 2 for a 432 watt hr pack, at the 1/2 hour rate they are rated at 12 amp hour. Very hard riding, stops and starts and hills on windy days, 7 miles, batteries basically dead. I never rode the bike easy, but, unassisted, 15 mph, easy riding, probably 15 miles no wind, slight hills.
Will try to answer 3 questions here. Does the belt slip, Is the suspension good, and an addition question, power to the wheel.
On the 2nd bike, using the short center, I think it is the last picture, yes, the belt did slip. Why, the motor cooling fins were touching the chain sprocket. I was unable to properly line up the belt. Slip was only on rocket acceleration. Further, the 21 tooth belt drive sprocket was not tightened securely, after a couple of hundred miles it came loose and wore the belt on the edge. I continued using the worn belt for several hundred more miles, I carried a second belt with me in case the belt failed. I moved the jackshaft last week from the top of the swing arm to underneath the swingarm and my centers are about 3 inches longer. I have a 180 amp controller times 24 volts, which is in theory over 4000 watts to the belt. It absolutely does not slip. This belt per the gates software should handle 1.3 hp continues duty 8 hours a day with moderate shock loads.
The suspension is weak. Front fork not up to the weight, but is solid, much better than the rst fork. The rear shock has an 800lb spring, the Bidwell maual specifies that this spring should be about 450 lb rated. So, I would say the suspension is about equivalent to a old style dirt bike, commonly refered to as a lead sled. I have the 450 lb spring ordered, just has not arrived yet. When it comes in I will move the bike seat back a few inches, use a different handle bar so that I will sit back further. This will take a lot of the weight off of the front forks, hopefully I will have a decent ride after these changes.
I should probably increase the gear ration to ll or even 12 to 1. During the winter, the motor never got above warm, controller never had a perceptable increase in heat. Now that air temperatures are in the mid 80's, my motor is hot after a 6 mi ride. To hot to touch for more than a few seconds. Changing gear ratios is a project. Move the jackshaft, add a link of chain, move the motor, buy another belt, drill some more holes. Current gear ratio is 10.4 to one. I have changed ratios often. On the first bike I think I had a 11/1 ratio and the bike was fast. Then, when I converted to belt I went 9/1 ratio, way slower, bogged down. Tried to find the sweet spot, went to 10/1, still not as fast. After building the 2nd bike installed a 10.4 to 1 ratio, now with a bike speedometer. No speedometer with former ratio's, but could not pedal at top speed at 11/1 ratio, could pedal at top speed with all of the others. Ratio changes take a lot of time, and, money. I have lots of belts and gears in a box, probably paid $300 for extra gears and belts. Eric says his is about 9 to 1 I think. Probably to steep but he weighs a lot less,
have you thought of adding some sort of spring tensioning device that would perform much the same function as a rear derailleur on a geared mountain bike? If you made it stiff enough you would have a predetermined tension that would be stable even as the chain stretches (spring constant). The one downfall I can really see with this is added parts, and if the tensioning device had enough mass in the wrong places, rough terrain or large bumps would greatly affect the tension for brief periods which could lead to trouble, however if you used a two sprocket design, again like a derailleur on bike, this could be greatly reduced.
Looks like your making some good progress.
My chain adjustment was not easy to accomplish. Also, I was using #41 chain, and the drive sprocket was a 9 tooth. You are using #35 chain with a 22 tooth drive sprocket. There is a break in period on the chain and using small drive sprockets accelerate chain wear. Also, I did not use top of the line chain because my supplier, purvis bearing was out of stock. Chain runs best loose, a little slack of about 3/16 or 3/8" overall deflection on the centers you are using would be considered a tight chain about as tight as needed. When the deflection is 3/4" or so overall, I started to feel it as I was cruising, kind of a bobbing sensation, the bike pulses as the chain bounces. Easy to make chain adjustment in very small increments is necessary. Looks like your on your way there, I am not sure about the spring, but, we have to experiment. I am still using my original chain, it has about 2 thousand miles on it. I use what the motorcyle shop said was the best synthetic lubricant, made by fuchs and is named silkolene. I use my current bike as transportation, 12 miles a day to work and to my parents house 4 miles away 2 time a week, take out inclement weather days and I am commuting about 70 to 80 miles a week. I can't think of when I made my last chain adjustment, but maybe now it is once every 2 months.
During your down time start looking at kick stands. The center stand did not work on my bike. I welded a bracket near the rear dropouts, this worked very well. If I had continued with this bike I would have purchased one of those double center stands so that it is easier to work on the bike.
I should have kept a log. My gear ratio's that I qouted on some previous replies are wrong. I changed ratios so much I forgot where I was at. The fastest bike was bike #1. Ratio 10 to 1 all chain all noise.
Then the gate belt arrived. 21 tooth primary and 64 tooth secondary for a 3.05 primary reduction. The wheel sprocket has 45 teeth. There was so much power at 10 to 1 I felt I could reduce the ratio. I used a 16 tooth on the jackshaft for a 8.6 to 1 ratio. No power, lower top speed. I used a 15 tooth on the jackshaft for a 9.1 to 1 ratio. Better, but still not a good as 10 to 1. I used a 14 tooth on the Jackshaft for a 9.8 to 1 ratio, getting better still, started hearing a little chain noise from using a smaller sprocket. With a bike speedometer installed 25.5 on the flat, 22.5 up hills, 28 mph max down steep hills. I need to purchase a 13 tooth jackshaft sprocket for a 10.5 to 1 reduction, hopefully before you finish your bike so I can get some speed results. As I said on an earlier reply, my motor is hot at the 9.8 to 1 ratio now that the weather is in the 80,s. Drawback, this smaller 13 tooth drive sprocket will increase the chain wear and increase the chain noise.
I have posted 2 replies, something in this website causes my keyboard to blink and beep about every third word. My number lock light goes off, then my caps lock light comes on. When I hit the preview comment button I go straight to google and off the website. This happened when I tried to respond to David Herron, the owner and adminstrator of this great site since the date of inception after the old V went down, it does not happen any where else. Hopefully, some one here can help. This is very frustating to me. I have tried different keyboards and mice. buttt, I am not computer innards literate.
Your making great progress. I spent june, july, august, septempber, planning, ordering, backordering, acquiring, putting parts together on your table is a lot of fun. Finally, I put together what I had. I spent hours, 100's of hours researching,, I am going to post, will reply again, beep every keystroke
continued, bbeeeps and all,
I just could'nt believe the speed and power of version one. I used this for to and from work at Home Depot. Exactly 5.7 miles from work. Texas is flat. Yeah, the 4 miles west from where I live to my Folks house. Easy pedaling with out a motor. Home Depot, I go thru a subdivision called Canyon Creek consisting of roads called Richardson Drive, Collins blvd and Alma. I have dial up and do not own a gps. I have a very heavy back ground in land surveying, I know what slope is. Some one on this site knows how to do the elevations on these roads, between Richardson and Plano TX, I would like to know what the true slopes are. On my mountain bike, or my Raliegh 21 lb road bike, it is 1st gear only. Worse, stop signs on the way up, stop signs on the way down. I am getting a little older, left knee clicks when I pedal, neck sore when I ride the 12 speed road bike, mountain bike more upright, more comfortable, but, June July August and September in Texas, no, you don't ride a bike to work. Well, if your in very athletic shape, you might. 8 am, 85 degrees, 5 pm 105 degrees, I can't do it. Anymore.
So, my bike is for transportation, concrete, 25 minutes from my front door to work, max. Sometimes only 20 minutes. 15 minutes by car, usually 20 minutes. Our needs are different, our choice of bikes are the same. My motor was very solidly mounted, I used the rack bosses that are, not brazed, Chrome Moly is "bronze welded". Do not worry about these lugs to use as attachment points, even the water bottle lugs, they ain't coming loose.
I had lugs right near the brake mounts. Use them if you can. My motor will bend the light aluminum mount you made. If, your jack shaft is similar to Eric's it may hold. If, you make it like I did, sprockets on opposite ends, the motor will torque to much. Probably too much movement. When I heard you say jumps, yikes, yikes. Trail riding, ok, jumps, no way.
Your coming along fast, get it on the road, addiction warning, next month will be my anniversary on electric vehicles, build it, ride it, make it better it won't stop.
just thinking a little bit about your problem, came up with an idea after seeing something out of a popular science article about individual wheel full suspension dune buggies. If you you do decide to experiment with tensioners, one idea would be to have a two gear set up, one above the chain and one below, both connected to one bar, and under rotational force, so that one pushes up and one down. this way if you have some sort of jaring force, it would make much less of a difference on the chain tension. However, again this means more parts. Personally I think this is less complicated than you are making it out to be. There are plenty of chain driven power transfer systems that do not rely on complicated setups, often simple is best.