Tomos Sprint conversion

[Jordan325ic]

Lurked here a while. I'm selling this project so I thought I'd share it before it's gone.
Link here: https://endless-sphere.com/forums/viewtopic.php?f=9&t=110600
Edit: Sold to a new home. Somebody is using it as a hunting rig, which wasn't my design intention, but it's actually pretty good at sneaking up on deer.

Found a Tomos moped on the size of the road with a "FREE" sign, only trouble was the gasoline motor and wiring harness were gone. Good conversion candidate! Technically this moped once had a VIN, it came back a 2009 Tomos Sprint 49cc, but the tax office showed it had never been titled and now could not be titled without the original motor which was long gone. So I peeled off the VIN sticker and chose to make it a slow, bike-lane friendly way to get around Austin's horrific traffic.



Had UnitPackPower make me a 48v17.5ah battery, 30a cont 50a peak, just small enough to fit into the 'gas' tank. The gas tank is a structural member so in order to counteract the weakness of adding the 'door' I welded studs to the frame and added thick aluminum brackets to hold the battery in. Been a year and no discernable frame flex or weakness. Charge port comes out the cap.
The battery build was as follows.
48v 17.5ah Samsung 35e cells, 30A BMS, cannon charge port, XT60 discharge port (dimensions not to exceed 300mmx90mmx80mm). +2A cannon charger (USA) +matching XT60 connector. 30A continuous, 50A max.
UnitPackPower on Aliexpress shipped $368





MagicPie 20" cast wheel slid right in and fit the original 16" moped tire. Fabricated 3 torque arms, quite short but quite thick, that fit onto existing nubs on the swingarm At this low power level it's fine. Welded a bracket for a mechanical disc brake.



Controller under the seat, with hidden kill switch (hardware store 20amp machine switch holding on so far!)

The controller plate was cut out of aluminum sheet. The plate has two tabs at the rear that slot into the seat support/latch bracket. There is a single screw in the front which screws into the original (still functioning) storage box mounting plate. So removal is just one screw and then slide forward. The controller had two mounting holes, which are held to the plate itself via long 5mm bolts. The edges are trimmed with some sort of door seal trim from amazon.

The battery is very snug, it does not move around at all when the door is secured. I used yoga mat material to cushion the battery all the way around, There is a plastic 'end cap' protecting the end of the battery from some metal internal supports at the point where the frame bends horizontal. The bolts holding the battery door brackets were welded to the frame.

Only instrumentation is a $5 waterproof voltmeter on the dash. DC/DC converter goes to switchable 12V system that runs the lights. Hi/low, tail/brake and speedo backlight. The mechanical speedo/headlight bucket are original.



Initially I was worried about legality, so I added this 'Electric Bicycle' certification. A year on I can say I needn't have worried. The police could care less.


With a 140lbs, 5' 7" rider we tested: 25mph cruising speed, real 25mi range.
200bs, 6'5" rider - 20mph cruising speed, real 20mi range.


Great urban commuter bike over the last year, it will outrun a Ferrari across town if there's any traffic. Moved to the country now and it's all 60mph roads, so this doesn't get used. Time to build something faster.

 

[amberwolf]

Neatly done. The label is a nice touch, actually, as is the XLR gascap. The only thing I personally would've done stylistically different is using a round analog voltmeter instead of the LED digital. (but I just like the old dial stuff)

Doesn't matter now, but the motor would run a teeny bit cooler without the clear plastic stickysheeting on the side covers, so the aluminum would be directly cooled by airflow rather than being slightly insulated by the plastic.


If you'd like to try selling it here, you can also make an ad for it in the Items For Sale - Used section.
https://endless-sphere.com/forums/viewforum.php?f=9

 

[neptronix]

Super nice and clean conversion. Good use for the 20" magic pie too, although i imagine your speeds are pretty low on 48v. Try 125v like i did

 

[Jordan325ic]

Doesn't matter now, but the motor would run a teeny bit cooler without the clear plastic stickysheeting on the side covers, so the aluminum would be directly cooled by airflow rather than being slightly insulated by the plastic.

You're right! I should have taken it off when I first got the motor, now it's horrible to get off... Comes off in tiny pieces.

Super nice and clean conversion. Good use for the 20" magic pie too, although i imagine your speeds are pretty low on 48v. Try 125v like i did

Yea, slow was the goal. 125V through a magic pie?? What controller?

 

[amberwolf]

You're right! I should have taken it off when I first got the motor, now it's horrible to get off... Comes off in tiny pieces.

Yeah, UV degrades plastic like that stuff and breaks bonds, so it no longer stays as one piece and stretchy/bendy, brittles up and fractures. (ever leave a trashbag of stuff (leaves, etc) out in the sun for a week or two? Then pick it up and it disintegrates in your hands..... )

My guess if you want tor emove it now is it would require something frictional across the surface, like the Magic Eraser sponge by Mr. Clean https://www.mrclean.com/en-us/shop-products/magic-erasers/magic-eraser-original that has some sort of gecko-grippy nano-surface to it. Feels wierd to hold, but it picks up stuff nothing else will, without scrubbing at it, so maybe it would work for this, if used dry?

 

[MorbidlyObeseKoala]

Really tidy finished product. Would you use UPP again for a new battery?

Obviously a 1500W battery is a different class of battery than some other ones we see on here, but UPP seems to have gotten some mixed reviews. Could be the users are abusing the crap out of the battery by letting it get wet or overdrawing it all the time but I don't exactly have a basement or garage to sacrifice to that experiment...

 

[Jordan325ic]

So far so good, battery is holding up well. They were responsive and good to work with regarding my very specific needs.

 

[Jordan325ic]

When I finally tried to get off the plastic wrap hub motor, lots of the paint came off with it. So I painted it all black. I like the look, but let this be a lesson to future generations. Take the plastic off sooner rather than later.

 

[amberwolf]

Looks better that way than with the GM stripes.

It would also look good enough ("original-ish") if you scrubbed the paint all off the hub itself (but not the "spokes"), and then oxidized the surface to match the "old aluminum" look of old drum brakes.