My Baja Minibike Project Begins

[Bitswap]

Hello everyone,

I'm a long-time lurker and have finally decided to build something small that I can use to roam a parcel I have in a remote location. It has some steep hills to traverse so I opted for a system with higher current. My electronics knowledge is extensive, but not with high-amp DC circuits. At one point in my history I designed PLL transmitters/receivers kits up to 450mhz using the PIC microcontroller among other things.

The Donor Is a Baja Minibike: http://www.bajamotorsportsonline.com/product_info.php?cPath=3&products_id=97 I'm planning on a 4.5:1 gear ratio to the wheel which has a 54" circumference. I'm aiming for good torque and 30 mph.

The Kit is this: http://www.cloudelectric.com/product_p/pk-el-m909-a300-axe.htm

For starters I'm planning on 12 3.2v 40ah LiFePo4 batteries wired for 36 volts.

I have some various other things coming in like a Cycle Analyst and Data Logger from Spark Fun.

Now for my endless stream of questions....

I'm tossed between using a Balance Charger like the Hyperion EOS 0601I Duo or building a BMS like the one designed here. It appears the danger of not using a BMS is when you wire the batteries in parallel. This is not my case however and should easily detect if an open occurs since my batteries will be wired in series. Plus the fact that the current version of the BMS here is in flux and entering its final stages of development and will not be available for planned completion date in a few weeks for rough trials.

Next is a tough one... can I charge my batteries while using them? Anything special I need to add to do this? I've yet to see a hybrid system schematic but it is possible that I'll tow a generator on very long trips to charge the batteries. My first thought was to get another bank and replace but that seems so inefficient.

Now the motor bracket. Most brackets I've seen are just a plate of steel welded to the frame perpendicular to the motor's drive shaft. Is that enough? It seems there would be lateral forces that need to be dealt with in the brackets design.

FINALLY!! Last question! I promise!!! (for now ) Many in the Baja Gas Community applied a Comit Torque Converter to increase low-end torque and high-end speed. This is an amazing device that incorporates a clutch and variable drive mechanism that increases in diameter as rpm increases... kinda like an automatic transmission. I can see this applied to my project since it 'should' decrease 'stalled' amps and give me the benefits of the gas application. Thoughts?

That's all the major questions for now.

Thanks in advance,
Bit

 

[mdd0127]

Sounds like a fun project. Every time I see a Rokon, I think, "Wow, that would be cool with a couple of hub motors!" Those little Baja bikes are a blast. I've never crashed as hard on a big bike as I have on little bikes though. "Don't worry, it's only an 80! Watch this!......Owwww!"


You could use a little weed eater engine and/or a couple solar panels, carry your gear on the trailer, and recharge while you're camped. It's a great idea.

That sounds like a whole lot of battery(36ish lbs?). I'm way too tired to do math right now though.

Anyway, build it! Post pics!

 

[mdd0127]

I didn't answer any of your questions.

As long as you're not planning on production, I'd just get a good charger and charge the batteries like you would with RC stuff. I don't think a built in BMS would really be worth the extra effort. Doesn't the controller have a low voltage cut off? I'd probably put a cell monitor on it, mainly to see whats going on, or catch any problems on the ride before they become issues.

If you want a true hybrid, charge while driving system, I believe that the motor/generator will need to be big enough to power the bike plus charge the batteries. I'd guess it's possible, but using a smaller supplemental system to trickle charge while driving would seem to me to be relatively difficult to engineer. You'd have to prevent the controller from being able to pull too much current through your generator setup.

As far as motor mounts go, I always try to build a little stronger than mathematically necessary. I wouldn't use one flat plate. I had to rebuild a bunch of single plate motor mounts at the plant, and support them from both sides, gusset, etc. You'd be very surprised how much torque a little electric motor can put out. If your motor twists, you will have chain issues.

Also, watch your weight on this thing and make sure the frame, axles and stuff are up to the extra weight. I don't know specifics on your bike but have seen some low quality parts/welds on ones like it. Just be careful.

I'd skip the torque converter/cvt. They're not very efficient. If you gear it right, you should have more than enough oomph to get that thing up anything you'd be comfortable going up on it, without a transmission.

Have fun!

 

[Bitswap]

Thanks for the reply mdd0127!

As luck would have it, I'm only going to receive 11 cells (one back-ordered) so I'm going to initially build a 24 volt system. That comes to about 28 pounds for the batteries. With the motor, controller and batteries, I'll actually be under the weight of the stuff I pulled off the frame! 150 lbs vs 137 lbs with a gross weight of 401 lbs. A 36 volt system will be about 5 pounds heavier. The obvious drawback here is my top speed will be around 22 mph... that's okay.

That's also easier on the Hyperion EOS 0615I Duo3 I ordered. I've been reading a lot on the battery threads and will probably build one of the BMS systems designed here when they're ready. Tons of good stuff there: Bulk charge then balance to top off is a great idea. Plus, I can use the Hyperion to charge my helicopter batteries!

I have one nagging question on that Hyperion charger and I've yet to find the answer. This is a 2x6s charger. So in order to charge, I need to threat each of the four cells like individual packs. No problem. Do I need to disconnect the 'series connection' from cell number four and five before charging? From the schematics I've seen here, it doesn't look like it but I want to be sure.

Your answer on the hybrid system complies with what I've seen out there: the generator must be able to push the motor current wise. This can be very expensive. What I've been looking at is a charge controller used in solar setups. The controller has hardware so you can trickle charge and not blow up the generator. They're designed for 12, 24 and 48 volt systems. What's nice about these controllers is you can use them as a power supply, a charger and can either have DC or AC input. For a 24 volt system at 40 amps, they're running around 400 clams. The voltage they put out will not over-charge the LiPo's either. We'll see, maybe in the future.

You have confirmed my suspicions about the motor mount! I'll have the fabricators take that into consideration.

And, the torque converter is out!

The battery monitor idea is excellent! They're cheap and who knows what quality batteries I'll be getting from China! I do have three spares so my luck may still be holding out.

(Edit) One more nagging question: Mount batteries vertically? Thoughts? My plan is to mount horizontally since it's much easier.

Thanks again!
Bit

 

[FeralDog]

Bitswap: first, welcome to the Forum!

That baja minibike may, or may not be what you need.
I ran a similar set of minibike concepts.
The virtue of the minibike is that those fat tires will handle soft sand and mud pretty well. The #1 downside (for me) was that the 5-8hp gas engine made the bike illegal on the street, unless licensed as a motorcycle.
I looked at a lot of minibike frames and "used" Bajas & Manco's to convert to electric for legality.
They are built for gas engines
In a form-follows-function design those minbike frames are made for FAT squat tires, heavy low center of gravity torquing engines, and minimal turning/shock absorbing front ends.

I looked for minibike adaptable hub motors, they are rare. If I was a to re-think the e-minibike for MY anticipated journey, I would start concept with 24 volt motor and 2 Optima battery's. Heavy, but that is what that frame was designed for.

Luck to ya!

 

[Bitswap]

Hello FeralDog!

Good advice all around and much appreciated!

I guess it's prudent to disclose the purpose of this project. I have a 640 acre parcel in a remote location at an altitude of 6500 feet off the grid. Since I live at 1500 feet, walking around the parcel wears me out. There are no roads and the ground is spongy when wet. Big tires are defiantly needed. Plus, it snows up there... about 8" max from what I've seen. There is a well 1/2 mile away and neighbors I'd like to visit about 1.5 miles away. A Rokon was actually my first choice.

This project is designed go get me around my parcel, get water and visit my neighbors. It will NEVER be used on a public thoroughfare or hard-surfaced road. I can load this guy in the back of my pickup and just cruise around my lot and enjoy. There are some 4x4 rocky hills I need to climb periodically as well. As the range of this vehicle is evaluated, I will use it to scout game in the area and possibly use it to drag the kills... elk.

I know the dangers of using 'knobby' tires on paved roads. This vehicle is strictly 'off-road' and at best will travel on established logging/fire roads.

I actually bought two of these Baja's at a fire-sale my company had for $150 each. I'm keeping one gas. I'm aware of the 'too-stiff' front suspension and seat problems. I was thinking of adding rear suspension or 'springing' the seat like they do on bicycles. Things can be beefed-up or modified. The thing is, I have something to build on.

Traversing rocks, loose gravel and sand to be acceptable for this bike. Although bumpy, not too bad. If the Baja frame doesn't work out, I'll probably put the electronics on a quad. I anticipate my average speed will be less than 10 mph since there's no way to go in a straight line in my lot because of the trees. I have a Suzuki DR-650 as backup which is much smoother but harder to load up.

I'll have to debate you on the seat not being comfortable... it's all relative. When I got back into motorcycles I bought a Honda 230 trainer and it was like sitting on a 2x4... OUCH!!!

Thanks for pointing out the front fork problems... Later,
Bit

 

[FeralDog]

In the area of creativity ... and just diddling the idea ... I wonder if you could keep the ICE engine and somehow Rokon-like the front wheel as an electric powered. Make a 2 wheel drive (as needed) for them mountains?

 

[wasp]

these look like the minibikes canadian tire sells?
i thought about using one for electric but decided to keep a eye out for a yamaha 350 bigwheel
much bigger(same engine as the 350 yamaha quads of the time)and a real suspention
i used to ride my buddies as a kid and loved it in the mud,snow(ice fishing) all around a fun bike
i will be watching this with interest
btw the canadian tire one is a 150 or 180cc

 

[Bitswap]

In the area of creativity ... and just diddling the idea ... I wonder if you could keep the ICE engine and somehow Rokon-like the front wheel as an electric powered. Make a 2 wheel drive (as needed) for them mountains?

GMTA. I've been keeping my eye out for a Rokon but If I were to use it, I'd keep the front/rear drive-train enact and replace the 15hp motor with an ME-709 or something similar with 15 hp nominal. They have all the bugs worked out on synchronizing the wheels already and why 'reinvent the wheel'?

The mini I'm building will help me evaluate gas vs electric motors since this is all new to me. Gas is odd, it yields 15 hp at a certain RPM and has a clutch. From what I understand, and electric has 15 hp at 1 RPM if you have enough amps... guess that's why the use them in diesel-electric trains these days.

Supports my pet theory of "Extremes Meet'. In the beginning we used steam, which also would have 15 hp at 1 RPM.

Good form Feral!
Bit

 

[Bitswap]

Hello Wasp!

My first criteria for the frame were the fattest tires I could find. I've been riding motorcycles forever and found when riding in snow, mud or sand that is the way to go. The next criteria is a low seat. It's nice to be able to stabilize yourself with your legs without straddling the seat and that means a low frame. If your climbing a rocky hill chances are you will lose momentum in which case you need to use your legs when you need to go forward or try again. I like it when I can put two feet on the ground.

I'm a motorcycle guy, not a quad guy and that is my preference. Guess I'm old-school. Who knows, that may change.

These Baja's are manufactured by various companies. A very successful design and I'm not surprised you see the same model in Canada. They have a pretty good following if you look for it. It's an 'adult' minibike, but then again, isn't the Rokon?

I'm going to try not bore the board anymore with these things. Next up will be the build and eventually performance specs. All the parts should be in this week and we can begin to fabricate.

Cheers,
Bit

 

[FeralDog]

Bitswap:
If you used your existing minibike, and "upped the gas motor" to an electric start version with alternator (say Robin Subaru say: Ex17 or Ex21 http://www.robinamerica.com/pmanuals.aspx?pid=8}
you may gain some ability to charge batteries. It will not be like a diesel electric locomotive, but it may supply you with a small ability to charge e-powered front batteries (depends a lot on the ICE alternator output).

At lower speeds (25mph) I currently can't think of a need to sync the electric front motor with the rear ICE. My e-bike front DD hub doesn't sync with my rear pedal (human powered) rear.
I guess the front e-drive may be useful 25-40% of your slower speed trip , rocks/hills squishy ground?
Thus an easy calculation for what you may need versus 100% full electric motive force.
The front existing forks could be locked solid (more robust), as many of them are just junk internal springs, and the tires give an adult rider sufficient "bounce".

 

[Bitswap]

Good stuff FeralDog.

Locking the front forks is a great idea!

I don't want to give the wrong impression here with regards to the use of this bike. My parcel is very flat and not rocky at all. I doubt there are any slopes greater than 10 degrees and no rocks that can't be avoided. Very mild terrain that any e-bike could handle if the ground were dry, which is most of the time.

Going to the well or neighbor's house is one hill I need to climb. It's about 25 degrees and 150 feet long with some rocks but nothing a 2x2 can't handle. Now the 'shortcut' is a 4x4 hill that I really don't need to take if this bike can't handle it.

My original plan for the hybrid defiantly needs explaining. I was going to tow a generator on a trailer to charge the batteries. That may come later. The generator I was going to use is a Honda 2000i, very light (48 lbs), quiet and efficient. I guess hybrid is the wrong term altogether. I got the trailer idea from Rokon. There is no way this generator can push the motor by itself. But if the batteries go dead, I can recharge them in a few hours or hopefully charge the batteries while traveling with a charge controller to extend the range... just experimenting at this point.

I hope this clears thing up a bit!
Bit

 

[Bitswap]

Hello Everyone!

All the parts for my project finally came in last Friday (04/16/2010). Oddly enough the first part I ordered was the last to arrive which was a sprocket for the motor. I have two 3.2v 40 ah batteries on back-order but I have enough to build a 24 volt system for testing. The batteries take a 6mm x 1.00 pitch x 12mm long nut and will accommodate a 5/16" crimp terminal nicely. These are the China types from EV Components. EV Components also include copper straps (WOOT!), nuts/washers for the terminals and some mounting brackets... totally unexpected.

I'm going to answer a few of my outstanding questions and add some comments that may actually contribute to this board's content!

Web Master: Feel free to move this thread to the appropriate build forum (mini bike/scooter).

First unanswered question: Should I position the LiFePo4's vertically? Answer: Yes if you want them to last.

Second unanswered question: Do I need to remove the serial wire to isolate the two 12v battery banks? Answer: It depends if your charger x2 is isolated or not. Determine by measuring resistance from power input to charging output. Megaohoms or 'opens' are a good sign.

This weekend I wired up the pack for charging. I bought some 12-pin male/female connectors from Rat Shack to provide the connections. Although they're only rated for 18 AWG wire (max), I used two pins for the main charging connections to the batteries and five of them for the balance connections. I'm not real happy with these cheap connectors but they will get me through the trials. Hyperion uses 12 awg for the main power leads and 22 awg for the balance leads.

I spent a lot of time analyzing the Hyperion balance connections. I have the EOS 0615I Duo III pushed by a Pyramid 12-15v 35 amp linear power supply. When looking at the balance connectors at the front of the case, you'll notice six black wires and one red wire. The black wire to the right is the 'most negative' and the red wire to the left is 'most positive'. This makes sense since it's designed for packs ranging from 1s to 6s: As you add more cells, you add more positive connections. Consider the right-most pin as ground, then add a wire for each cell progressing to the left if you have your cells wired in series. For mine (4s) I used five wires with the last one (12v) landing on the fifth pin from the right. Look at the Hyperion schematics (very poorly done) because sometimes they skip a pin.

After checking for shorts and attaching to the Hyperion, I was glad to see the charger was happy with my arrangement. With LiFePo4's, you need to select 'A123' type batteries to get correct charging.

So that's where I am in the build. Next is to have a pro build a motor bracket for me while I start working the the controller and associated parts (Cycle Analyst, Data Logger, etc).

A clear winner in this project so far is an 8-ton hydraulic crimp from Harbor Freight. The awg's are very very off but will work for 12 awg terminals and 6 awg terminals (max). Undersized dies are well known for this but for 50 clams it's hard to beat. I tinned then crimped then re-flowed my terminals... probably overkill, but it's all good in the long run.

Later,
Bit

 

[Bitswap]

Hello All.

This is an update of the project so far... Pictures will come later.

The only wielders I found work Monday to Friday 8:00 am to 5:00 pm and are far from me. So I decided to build the battery and motor housing myself out of wood since I don't know how to wield or have the equipment. But I do know how to work wood.

I built the boxes from 3/4" and 1/2" plywood and fit them to fit the bottom of the frame with the batteries forward. That's where I am now. The boxes are ready for mounting bolts to be finalized. It is a very snug fit overall.

Things should go quickly after I get the batteries and motor mounted.

Later,
Bit

 

[liveforphysics]

In the area of creativity ... and just diddling the idea ... I wonder if you could keep the ICE engine and somehow Rokon-like the front wheel as an electric powered. Make a 2 wheel drive (as needed) for them mountains?

FWD is absolutely not needed for obstacles of any size or type. Pulling as much weight off the front end will get you loads better results for handling obstacles than powering it.

 

[John in CR]

FWD is absolutely not needed for obstacles of any size or type. Pulling as much weight off the front end will get you loads better results for handling obstacles than powering it.

What about going up mountains off road? One of our member photographers built a 2wd and said it was great, but just couldn't find the right hub motors for his low speed inclines. I understand all that weight in the front wheel would be bad for performance riding, but otherwise why wouldn't 2wd be better off road just like 4wd is better?

John

 

[mdd0127]

2wd can come in handy in sand and mud because a non powered front wheel will act like a brake when turned. Yamaha built a 2wd dirt bike and the riders loved it in the sand. Also, around here, in the mountains, 2wd could be very handy. Sometimes, the trail is too steep/rocky to safely get your front wheel lifted for an obstacle. With 2wd, it will pull over roots and rocks instead of running into them. I've been toying with the idea of having a 2wd package option on my bike. Then it could have regen too. 2wd and regen, while arguably not worth the effort for most riding would come in very handy on gnarly mountain trails.

 

[Bitswap]

Huston, the spacecraft has cleared the tower...

What a busy day today! I finalized the mounting brackets and ended up completing the mini bike... well about 80% done. I took it for a ride about 2 am my time!!! WHAT A BLAST!!!!!

I was worried about the wood braces but they didn't even flinch. Wow that ride was fun!

I still have to program the Altrax and install the Cycle Analyst but I now have a working bike. It handles well in the dirt, grass and sand. Right now I have an 11 tooth sprocket on the motor and goes pretty fast for a 24v system. I'm impressed so far. Haven't climbed any hills yet so we'll see how the torque goes.

This is what I did today:
- bolt the battery and motor boxes to the frame
- dremeled the chain to length (couldn't find a breaker)
- put all the electronics together including the throttle and kis.

Yes it's ugly, but it's mine. Things will change as I work on it some more and evaluate its performance. Let the trials begin!

On the forward weight vs back weight, I've found the lighter the front the better. But, I have no choice with this guy cause the frame is so small. I did ride it in some sand and it appears to be okay. If you look at the Baja, you sit over the rear wheels, so it's a given you'll always (hopefully) have most the weight on the rear tire.

I'll take some pictures tomorrow to show you what it looks like.

Later,
Bit

 

[Bitswap]

Sorry for the lack of pictures, but I just finished my trials, the sun is setting and I'm totally confused.

How accurate is the Cycle Analysis (CA)? According to it, I'll get about 47.5 miles on a charge using eight 40 amp batteries. That does not seem possible since most posts I've seen are running about 55 watts per mile. Mine is showing 21.4 watts per mile.

I set the millimeter circumference to my tire (1524mm or 60 inches) on the CA and made sure it was registering the magnet. My max speed is 29 mph which agrees with my calculations. I'm using a third party shunt resistor that measures 50 mv per 100 amps. I tried to measure the R-Shunt but the resistance was zero, not in the megs as per the CA manual.

I drove 10 miles through the roughest terrain I could find including lose gravel and deep sand. I just don't believe I can get 47 miles off a single charge especially since the motor is only about 80% efficient. To make matters worse, I didn't connect the CA till after about a mile of trials the other night.

I'm not complaining, but these numbers aren't even close to what I predicted except for the speed. My numbers say I should only get about 24 miles on a charge or 60 watts per mile. If the CA numbers are correct, then I built one heck of a minibike!!!

To make things even more confusing, as I watch the watts used they NEVER go below 21 watts. They more like averaging in the 80's or so. And when torque is needed it will register about 1000. What's up with that??? If I'm averaging 80 watts when running, how can CA possibly tell me I'm using 21.4 per mile? I'm at a total loss on this.

Here are the stats from the CA:

Ah:8.463
Miles: 10.060 << about right
Volts: 26.2 << started at 26.4
Watt Hours: 214.710
Watts / Mile: 21.4
Amp Max: 109.4 << soft sand, steep hills, no problem
Max Speed: 29.00 << about right
Avg Speed: 9.010 << about right
Time: 1.07 << about right

Thanks in advance,
Bit

 

[Bitswap]

I think I'm going to answer my own question posted above.

"Never overlook the obvious"

The 'mOhm' in the CA manual stands for Milli Ohm, not Mega Ohm.

Since Volts = Amps x Ohms, and my shunt is 50 mv at 100 amps, I can calculate the ohms, which should be 0.500 milli ohms in High Range mode of the CA.

I can verify this by watching the amps used by the Altrax controller which will display amps continuously with my laptop. Plus I have a clamp amp meter that will read dc amps.

We'll see.

Later,
Bit

 

[Bitswap]

Hello All,

Another busy day. Everything came together and is finally making sense.

Friday (May 7, 2010) I put the controller and associated parts on a 'real' platform instead of what I had. With the final design, I no longer need to remove the batteries to charge them. Sometimes it's the little things that count. I changed the mOhm (milli ohm) value on the Cycle Analyst (CA) to 0.500 and drained some power at the local school. Upon charging, I found the Hyperion charger versus the CA amps/watts was only 3.75% off... I'll take that!

Today I started by verifying the odometer. It was off by 0.088 miles (per mile) on the high side. Made some adjustments and now it is spot on. These 'mileage' trials took about 10 miles to get right and charged it again. Again, the CA numbers agreed with the Hyperion numbers.

So now with the wattage and miles correct I can finally get some good numbers and I'm impressed. I'm averaging 43.2 watts per mile! I ran the batteries down to around 88% discharge and got 21.72 miles. 70% discharge will give me 16.51 miles. The terrain I traveled was much like I'll see at my parcel. On graded roads, the numbers are even better. I guess the motor is over-powered for this application. It never got over 120 degrees. My top speed with an 11-tooth motor sprocket is 27 mph. I can easily go to 12 teeth but that could be scary without a front break.

Remember, this is using eight 40 amp LiFePo4's...a 24 volt system.

That's not bat IMO, I estimated between 55 and 60 watts per mile. At the end of the long-range run, my voltage at 'idle' was 25.8 volts and under a load was 21.5 volts. I didn't want to push it but think I can get a few more miles out of the batteries if I wanted to go to 100%, but I want to keep it to 70% to maximize recharge counts.

The wood brackets for the motor and battery boxes are working very well, I see no stress points or cracks so far. Guess I should prime and paint these guys.

Big winner this post is the Cycle Analyst!!! Man this little device is worth it's weight in gold. Tons of good info from it.

Big losers this post: DC clamp ammeter and ampage reading from the Altrax program. Totally worthless.

Later,
Bit

 

[Bitswap]

Hello everyone!

This project is finally coming to an end! I got the dashboard built, wired-up the SureFun data logger and got it working and got a Cell Logger 8S wired up. My Pyramid power supply died, but Amazon replaced it within days!!!

I still have lots of minor things to do but most is minor and not relevant to this board.

I finally took some pictures and am going to try to post them here. We'll see how that works out.

The first picture is from the right side. The box in the front houses the batteries with the controller on top.View attachment Baja-01-Right.jpg

And the Left Side..
View attachment 6

Here's a close up of the left side battery and motor boxes.
View attachment Baja-04-LeftCloseup.jpg

From the right looking at the motor and housing.
View attachment Baja-06-ContRight.jpg

And the instrument panel... it folds down for easy access. Top-down: SureFun data logger, Cycle Analyst Cell Logger 8S.
View attachment Baja-07-Dash.jpg

Here's a detailed view of the motor housing. It actually fits into a dado of the battery box for stability. The black line you see on the back of the battery box is oil... oops.
View attachment Baja-09-Chain.jpg

The front of the battery box took some work to get it to fit.
View attachment Baja-10-Batt.jpg

And finally, I had to install a 300 amp switch to break the serial connection of the two 12v packs because the Hyperion charger didn't like it if I didn't. Talk about Bulky!!! The two white Rat Shack connectors serve dual-purpose: balance wires for the Hyperion and connectors for the Cell Logger 8S. Sweet!
View attachment Baja-11-Balance.jpg

Only thing left to do is stain and waterproof the wood, but I'm not in any big hurry to do that. Right now I'm running an 11 tooth motor sprocket which gives me 28 mph. More data on the watts/mile is incoming but so far looks like around 45 watts per mile in rough terrain.

I'll update performance specs later as I gather more data.

Cheers,
Bit

 

[bzhwindtalker]

looks cool ! you don't have acces to metal junk and tools? it would be more durable when painted? do you have a metal support under the wood to hold the motor? But your plywood seems to be really strong, 12mm?

 

[Bitswap]

looks cool ! you don't have acces to metal junk and tools? it would be more durable when painted? do you have a metal support under the wood to hold the motor? But your plywood seems to be really strong, 12mm?

I do have access to metal and tools but don't trust my wielding abilities. I'm good with wood and wanted to get this project on the road quickly. I don't think painting will effect the structural integrity of the wood. Wood is very viable and strong. Some airplanes are made entirely out of wood, like the British Mosquito. Some aircraft today use wooden wing spars.

Wood has many advantages over metal. It's alive and flexes. The fatigue strength is incredible. Plus, the strength is in the design and joints. You'll notice the motor is in a 'box' that supports stresses that may be imposed by twisting. The bottom and front are made from 3/4" plywood and the rest from 1/2" ply. All joints are dadoes and rabbits. There is a flat metal plate that runs along the bottom of the frame that the boxes are attached too.

From my trials, I haven't heard the motor box complain a bit... which actually surprised me. I need to add a top to that box and attach it to the rear metal shaft under the seat. But now, that thing doesn't move a mm and is VERY solid.

 

[Bitswap]

Hello Everyone!!!

I just got back from a two-week trip to my parcel, well last Saturday, and decided to make a final post and answer any questions regarding this project and let this thread die.

I have a montra for this bike: "When you turn the throttle, it's going with-or-without you!"

The torque and power of this bike are simply amazing! It took everything I could throw at it including sand and rocky hills with slopes at around 35 degrees (scary). I would have never though a 4.5 HP nominal motor with 14.5 HP peak could have so much power. It simply 'blows-away' the 6.5 HP ICE it originally came with... not even close.

The wooden bracket I made for the motor didn't even flinch. I have no problems with that design at all! All I have to do is sand, prime and paint it and the battery box and those part will be complete.

The bike went two weeks on one charge. I usually drove it twice a day. I put 7.79 miles on it, averaged 81.3 watts per mile and used 24.5 amps. Average speed was 4.18 mph. Obviously the big winner here was the Cycle Analyst. I couldn't read the Cell Analyzer in the daylight. The Hyperion charger matched the amps used on charging.

What is really nice is I can drive it up the ramp into my pickup, pick it up and turn it around, and drive it down the ramp. I couldn't be happier with this bike. I spent a lot of time cruising around my parcel and following game tracks. This bike makes tracking so easy! The only sound it makes is that of the ground crushing under its wheels.

I do need to do something about putting springs on the seat like a bicycle has. Running on rough terrain got very bumpy. I tuned the front shocks and they appeared to work well.

Thank you all for helping me out here and making this project an overwhelming success!

Laters,
Bit