Harold in CR's First Build

[Harold in CR]

Well, it's been a LONG time coming , but, now I have nearly everything I need to kill myself. :lol: :lol:

Cut a head post out of a BMX very heavy frame, and welded it into a round tube frame that I fashioned from parts laying around.
Bought a 14" Moped Yamahopper front wheel and put a decent tire and heavy duty tube in that.
Had to cut a set of forks out of another frame, and cut and chisel the aluminum steering post out of the fork tube. Had enough extra so no sweat there.
Bought a 2 speed motor from John in CR, and put a decent tubeless tire on that wheel. It comes in at 17½" height, so matches up close to that 14" front wheel.
Have a rear shock from a Kawasaki moto that I bought parts off of on Fleebay.
Bought an Infineon controller that needs the 72V mod resistor and check out the caps. A Leo controller is in the future when money frees up a little.
Bought a new full twist throttle.
Bought one of those $12.00? V-A-Ahr meters that were shown on the forum. Bought a V-A meter. all are LED.
Got a freebie 72V-12V Dc/Dc converter for lighting and such, to include an E-Airhorn, if I can locate one.
Made a deal with a member-vendor for nearly 500 26650 M1-A LiFePo4 cells.
Bought a wad of accessories also.

Now, to get it all put together.
Inside the frame, I will put a center plywood panel, similar to what Aussie Jester did, to mount the batteries to. They will stand upright and be in long rows of 23S 18P, if I go to that setup. :lol: The batteries will sit on "Shelves" that stick through the center panel, and, will be built similar to a spice rack, on a kitchen cabinet door.
That will make them firmly attached with strips mounted underneath to support the weight. All will be tied in real well, and sit in shredded foam carpet underlayment, to absorb all the roughness from the rocky ¼ mile ride in and out of where I live, to reach the blacktop.

The frame will be beefed up with ribs of some sort, so I can stretch light weight plastic fairings over the frame to protect the batteries and keep them weather resistant, and, keep out the wandering fingers.
Controller will-should fit under the moto type seat above the rear wheel, protected from the elements, but, hopefully have an air stream focused on it to help cool it if need be.

Distance inside the frame at the curved seat area is 10½" high. Length is 26 inside and wheelbase is right at 50" c/c of the axles.

The frame is a combo of cruiser-dirtbike-cargo bike, kinda. It will be our main source of transport, so, I need to be able to strap the little woman on the back, along with her back pack, when she goes to the big city and back. Should be able to carry 50-75# of feed and or groceries on the back. I'm sure I have left out a bunch of stuff that will need to be added later on. Top of frame tube is 23" from the floor, so, my short legs will be comfortable sitting on it with feet flat on the floor. Down here, these little guys mostly ride high sitting dirt bikes on the road. They can barely balance it sitting still with tippy toes touching the road on one side or the other

Still need to get the steel box tube to build the swingarm. That whitish piece of 2 X 2 represents the swingarm position.

Only time will tell.

Here is what I have so far. It's a slight;y different view with handle bars showing better in the second photo. They are not what be used, but, works to get a "feel" sitting on the frame. I have short arms, so, had to adjust things to get a comfortable feel.

 

[randel24]

Harold, relax that fork angle, kick that front wheel out some . It looks like those forks are way to vertical! Ithey will make handling way to sketchy. Will be checking in. Randel

 

[motomech]

gee, I hate to be rude, but I see lot's of things that need to be rethought.
But for starters, I will just mention the things most likely to kill you.
Aside from the lack of fork rake, I would question the use of a Yamahopper frt. wheel. A QT50 weighs around 100 lb.s without the rider and with 23S/18P[?]of batteries, I believe it will fold at the first impact with a Costa Rician pot-hole. The forks are pretty iffy for that thing as well.
Is there some reason you don't want to convert a motorcycle?

 

[Harold in CR]

OK. I very carefully took the head post angle from the MTN Bike frame I took the fork from. Then, I drew out the whole frame design on a large piece of cardboard. Then I carefully kept things relative to that drawing. I don't like the frame nearly hitting the front tire IF the fork gets bent. Right now, it does have enough clearance to bottom the suspension at ¾" from hitting the frame. Thanks, Randel

Motomech
Compared to a bicycle front wheel, the one I used is heavier, with stronger spokes. This is my first build. The frame is longer than a Moped, so, I figured less weight strain on the whole front end. I will be sitting in the drop curved section of the frame. Any additional weight will be rear ward of that, and right above the rear suspension.

I won't be going the whole 18P battery right away. I have been looking for a used blown up 125 Moto frame. That would be my second attempt. I also don't plan on going WOT down the hwy right away, either. Need to see where things flex and find the weak places, before going full tilt.

Appreciate all the input. I will do some studying and see how things need to be altered.

 

[motomech]

I hate to sound like a broken record, but I lived in Costa Rica for 10 years and I know how the roads can get. I've been put down by a water filled pot-hole on a full size BMW. And I wasn't going fast.
There are plenty of dirt bikes with bad motors around, or if nothing else, go to transito's boneyard and pick up one of the dozens of rusted out bikes they have in their pen. They probably wouldn't sell you a complete bike, but one of the rusted out ones, they might let you have for cheap.
I was a motorcycle mechanic for 22 years and I have an eye for what will work and what won't....and you have a long way to go.
Pura Vida

 

[Harold in CR]

OK. Checked the geometry for bicycles and 73° is average. That would be 17° as I can measure it. Mine is 11°. So, somehow, I will try to change that.

If you see so much wrong, I would like to know everything you see. Give me a list.

 

[John in CR]

Harold,

The guys are right, you really can't ride it like that. The head tube angle is only one aspect, and for a given fork is the cause, but you can't look only at head tube angle. Trail is the end number you have to look at as related to stability especially at speed. Trail is the distance between a straight line drawn through the center of your steering axis, your head tube, to the ground and a vertical line drawn through your axle, which is where the tire touches the ground. Laying the head tube angle back and a larger wheel size both increase the trail. The offset from the steering center built into the fork, a smaller wheel, and compression of the front suspension, all decrease trail.

An MTB isn't a geometry to copy for use on an ebike unless the plan is to ride your ebike at slow pedal bike speeds picking your way through off road trails. That's because they typically have a steep head tube angle and a short trail for more responsive and quick steering. While that may sound good for the road, especially that rocky road the last 1/4 mile to your house, it's not what you want on pavement at moderate speed and above, because it becomes overly sensitive and unstable. Stability is what you want on the road.

My blue bike that you rode started as an MTB frame, and I laid the head tube back a bit from how it was on the bike, but the trail ended up less than 2" due to the fork having more offset than the bike's original fork. I rode it for a few days, and while it was kinda ok, I felt like I had to keep both hands on the bars at all times, and when the CG was more forward like tucking low for better aero into a headwind, the bike got squirrely. I hacked the head tube off and laid it back some more. I overshot my 3" trail target, and ended up more than 4". The result is at very slow speed, just a few mph, steering is sluggish making it difficult to stay dead straight at extremely low speed. That's only an issue riding along with someone who is walking. Above that speed and right up to 60mph it tracks like on rails. In fact, when I get on the highway and tuck down to go for max speed, it's so stable that I hold the bar with one hand and bring my left arm in to center for better aero. My Super V isn't even close to that stable.

Here's a couple of drawings showing what trail is and how the offset of the fork itself reduces trail. The reason yours sticks out like a sore thumb is that you actually have negative trail, and you really should change it even before taking a test ride.

 

[motomech]

Another item is torsional rigidity. It's hard to tell from a 2 dimensional photo, but I don't see anything to prevent frame twisting when one wheel takes a side impact. The resulting deflection would put the two wheels out of alignment, with resulting instability.

 

[Harold in CR]

Yes, not the best fork. I just don't have $100.00 for the new one. Thanks for the photos John. MUCH help.

The frame is only shown as a design, for now. It will have more rigidity built in. I wanted to get input before I built the swingarm, and, appreciate all that was stated. There is plenty of road clearance for the shorter fork. It will probably increase C/G also, being lower.

Thanks guys.