Hi Folks,
I thought some of you might be interested in pictures of my RC-middrive build for the HP Velo Scorpion FS recumbent trike.
My wife said three things when I told her I wanted to put electric motors on our trikes (obtained as stable comfy more old-age-appropriate ride-replacements for our mountain bikes):
1. Don’t you dare trash my trike.
2. Make is not scary (for a non-tech person).
3. Make it pretty.
My own goals were 1) to easily make the run from town up to my house (~3000 vertical feet in 4.5 miles), 2) run efficiently at both low and high speed.
I tested a BMC hub-motor but didn’t like the narrow power band, nor the gear knashing noises, and was kinda turned off with the required rear-fork mods, the disc brake misfit, and having to bend the fork to get in a 9-speed cassette. Encouraged by this forum, I chose RC mid-drive with a belt reducer, since, in part, I always loved the look of the MadMax movie's Interceptor, which had it’s way-cool big timing-belt turbo spinning up at the flick of a switch. A belt-reduction unit would be user field-serviceable, and that seemed a big plus. The main problem with the HP Scorpion is that because of the full suspension and complicated driveline, there is little usable space behind the seat to locate a reduction unit, as has been nicely done on a number of other trikes that have squarish, spacious, and/or extendable frames. Fortunately Matt S (recumpence) offered to build me a couple of flexible and beautifully-made 2-stage reduction units that I could modify to fit under the front boom. The key idea was simply to rotate the boom extension 180 degrees to put the symmetric (i.e. works the same CW or CCW) Schlumpf high-speed pedal-drive on the left side. This allowed for installation of a double freewheel and a jackshaft over to the main chain-line on the right. Here are some pictures of the build.
The main modification to the two stage davinci drive was to replace the 2nd stage bearing tube with a new one, holding a keyed 5/8 shaft (vs. unkeyed ½”). This allowed two ENO freewheels (linking to the 8mm drive pulley and the pedal chain) to be squeezed side by side in the small area between the left pedal and the boom.
Black parts by Matt, silver parts and chain rollers are my mods. Total weight with Astro 3215 motor = 11 pounds. My mods (heavy ENO freewheels, bigger shafting & bearings etc.) added ~3 pounds.
My wife and I are short, so everything is tight. But it all runs smooth with no scrapes or bindups, in the first few hundred miles anyway. The motor unit is held by two super-neat recumpence boom clamps, and by extending three large existing frame bolts into custom attachments I put on the reducer body. Nice thing about the Schlumpf high speed drive is that with motor at full speed, you can still pedal-assist at a reasonable turnover rate (about 90rpm).
View attachment 5
The pulleys are 20-80 (for the 5mm pitch x 1”wide 1’rst stage), 14-50 (8mm pitch x 7/8”wide 2nd stage), and 16T driving a 9 speed cassette (11T – 34T) in the back.
After foolishly showing my wife some videos of LiPo’s burning, I calmed her down a bit by installing quick release battery mounts. Though under the seat (well, there seemed no better place, while keeping the cable runs very short), a quarter turn of two huge wingnuts and a light pull gets the thing off. I sure would hate to torch these trikes (see my wife’s point #1).
Some specs: Fullup weight (with one 13 pound 12S, 16Ah battery) about 73 pounds. Min ground clearance: 4.5”. Top speed with AstroFlight3215 – 40mph, Astro3220 – 45mph. I’m sure a different gearing would get you over 50, but holy crap, even 40 seems pretty scary to me! It takes about 7Ah to go the 9 miles home from downtown (4.5miles on the flats and then 4.5 miles up about 3000 feet). And the Astroflight3215 + tooth noise makes a kind of beautiful spin-up whine as the power kicks in.
Great fun, and only possible after reading so much valuable information here! Thanks to all for a great forum.
John
Boulder, CO
PS – If anyone is into 3D, there are some stereo pictures of the trikes at http://hart3d.com/projects/Projects.htm
I thought some of you might be interested in pictures of my RC-middrive build for the HP Velo Scorpion FS recumbent trike.
My wife said three things when I told her I wanted to put electric motors on our trikes (obtained as stable comfy more old-age-appropriate ride-replacements for our mountain bikes):
1. Don’t you dare trash my trike.
2. Make is not scary (for a non-tech person).
3. Make it pretty.
My own goals were 1) to easily make the run from town up to my house (~3000 vertical feet in 4.5 miles), 2) run efficiently at both low and high speed.
I tested a BMC hub-motor but didn’t like the narrow power band, nor the gear knashing noises, and was kinda turned off with the required rear-fork mods, the disc brake misfit, and having to bend the fork to get in a 9-speed cassette. Encouraged by this forum, I chose RC mid-drive with a belt reducer, since, in part, I always loved the look of the MadMax movie's Interceptor, which had it’s way-cool big timing-belt turbo spinning up at the flick of a switch. A belt-reduction unit would be user field-serviceable, and that seemed a big plus. The main problem with the HP Scorpion is that because of the full suspension and complicated driveline, there is little usable space behind the seat to locate a reduction unit, as has been nicely done on a number of other trikes that have squarish, spacious, and/or extendable frames. Fortunately Matt S (recumpence) offered to build me a couple of flexible and beautifully-made 2-stage reduction units that I could modify to fit under the front boom. The key idea was simply to rotate the boom extension 180 degrees to put the symmetric (i.e. works the same CW or CCW) Schlumpf high-speed pedal-drive on the left side. This allowed for installation of a double freewheel and a jackshaft over to the main chain-line on the right. Here are some pictures of the build.
The main modification to the two stage davinci drive was to replace the 2nd stage bearing tube with a new one, holding a keyed 5/8 shaft (vs. unkeyed ½”). This allowed two ENO freewheels (linking to the 8mm drive pulley and the pedal chain) to be squeezed side by side in the small area between the left pedal and the boom.
Black parts by Matt, silver parts and chain rollers are my mods. Total weight with Astro 3215 motor = 11 pounds. My mods (heavy ENO freewheels, bigger shafting & bearings etc.) added ~3 pounds.
My wife and I are short, so everything is tight. But it all runs smooth with no scrapes or bindups, in the first few hundred miles anyway. The motor unit is held by two super-neat recumpence boom clamps, and by extending three large existing frame bolts into custom attachments I put on the reducer body. Nice thing about the Schlumpf high speed drive is that with motor at full speed, you can still pedal-assist at a reasonable turnover rate (about 90rpm).
View attachment 5
The pulleys are 20-80 (for the 5mm pitch x 1”wide 1’rst stage), 14-50 (8mm pitch x 7/8”wide 2nd stage), and 16T driving a 9 speed cassette (11T – 34T) in the back.
After foolishly showing my wife some videos of LiPo’s burning, I calmed her down a bit by installing quick release battery mounts. Though under the seat (well, there seemed no better place, while keeping the cable runs very short), a quarter turn of two huge wingnuts and a light pull gets the thing off. I sure would hate to torch these trikes (see my wife’s point #1).
Some specs: Fullup weight (with one 13 pound 12S, 16Ah battery) about 73 pounds. Min ground clearance: 4.5”. Top speed with AstroFlight3215 – 40mph, Astro3220 – 45mph. I’m sure a different gearing would get you over 50, but holy crap, even 40 seems pretty scary to me! It takes about 7Ah to go the 9 miles home from downtown (4.5miles on the flats and then 4.5 miles up about 3000 feet). And the Astroflight3215 + tooth noise makes a kind of beautiful spin-up whine as the power kicks in.
Great fun, and only possible after reading so much valuable information here! Thanks to all for a great forum.
John
Boulder, CO
PS – If anyone is into 3D, there are some stereo pictures of the trikes at http://hart3d.com/projects/Projects.htm
