kiltedcelt said:
While I like the looks of the Velove quads, and understand why're they're made the way they are, I feel it's too complicated and at this juncture there's WAY too much extra work in trying to put together my own multi-link front and rear suspension.
another problem with quads is that in many areas, quads of any kind are not bicycles, and may not even be a legal class of vehicle or hpv to use on public roads or paths or sidewalks. many places use some variant of the definition "a bicycle has a maximum of three wheels in contact with the ground", which makes any "normal" quad not a bicycle, and there is not usually any other definition it matches either. whether that makes it a "gray area" or simply not allowed at all depends on law enforcement in the area more than anything else.
for example, they would not be legal here in arizona, although leos would be unlikely to care, they could use that against you if they had any other reason (or desire) to stop you in the first place.
that's the primary reason i have never built one. the secondary is the extreme (for me) complication of suspension (and/or complicated frame design) being required in order to keep traction on all the wheels.
Also, a delta configuration, like a Hase Kettwiesel, means I'm able to have a much tighter turning radius. I started looking at differentials and such, and I see a company makes a freewheel type differential where they've already done the work for you and you just need to supply your axles.
unless it's some radically different design than i've ever seen, then as i noted before, a fw diff doesn't do what you will want it to do. it will force you into a wider turn, and prevent a tighter one, if the power goes thru that, because it will put the power to the inboard wheel, when it needs to go to the outboard wheel.
you'll need something like a peerless diff or similar to spread the power appropriately to each wheel in a turn. these are not all that expensive if you don't need massive torque thru them. $150-200 for lawnmower/lawntractor types. probably less if you poke around.
if you provide a link to the company in question, or at least to someplace with pictures of their setup, i can look at it and tell you if it will do what you want.
1. Two separate axles, but the BBSHD drives only one wheel.
just like any other one-sided-power system, it works well enough in a straight line on smooth terrain. if you are at faster speeds on bumpy terrain such that the powered wheel loses traction it can result in undesired behavior. when pedalling is the power source that's not a problem because you can naturally lessen or stop power input easily as needed during the actual bumps, but when using a motor the delays in the system depending on control method may not allow this.
in turns, it only works really well when the powered side is outboard. when it's inboard, it's difficult to make a tight turn unless you stop powering the wheel and then just coast thru the turn.
if you really can only power one wheel, perhaps the front wheel would be a better choice. if you remotely control the bbshd from just a throttle, and/or a separate pas sensor on your regular cranks (whcih also solves a number of other mechanical issues various people have with middrives built onto the cranks), then the bbshd can be mounted on the fork of the front wheel, and power that wheel directly via chain. use a bmx rear hub for the wheel and a single speed freewheel, or use a fatbike fork and a regular rear wheel hub with multispeed freewheel. then you just have to put a derailer hanger on the fork with an adapter plate at the dropout, and make a mount for the bbshd above or behind the wheel itself, that mounts to the fork crown or stanchions.
2. A solid axle in the rear - BBSHD drives both wheels equally, but as I understand it, in a turn there is scrubbing on the wheel that is moving less (the inside wheel in a turn?), or do I have that backwards and the scrubbing is on the outside wheel? Also seems like a less than favorable solution.
scrubbing is on the inboard wheel, as it's trying to push forward as hard as the outboar wheel but can't. it's also going to try to push you in a straight line and won't tend to have as tight a turn radius.
One thing that occurs to me about the above 3 options is how do I provide suspension for the rear? I've already decided on a suspension fork for the front, and I'm mulling over 20" front versus 24". A lesser consideration would be whether I can make this with fat tires - full 4" wide front and 4" wide for the rear, or at least maybe 3" if I'm going with 20" rear wheels.
if you don't use small wheels, and go for 26" or larger, you may not need as much suspension, because larger wheels roll over bigger terrain problems than small ones.
you could use fat tires to help with the vibrationally-annoying stuff, though they won't help all taht much with big hits, especially if they're small diameter.
if you are going fast enough on rough terrain to need suspension, there's a number of ways you can do it, but it's all going to complicate your drivetrain, frame design, and cargo handling (because suspension response will change with loading--if you design it to respond best with a heavy load, you'll probably bounce all over the place when empty, and it raises the deck that much farther above the road).
Final consideration for deck height - I want to keep the rear at 20" wheels with the cargo deck ABOVE the wheels primarily so that I have a completely flat platform for loading materials including sheet goods and/or self-contained cargo boxes similar to what the Velove quads can haul.
some thoughts, based on my experiences with various cargo and various trailer and trike designs i've used so far:
unless you have a requirement for narrow track width, then as long as the larger diameter wheels are spread far enough apart for the max width of the cargo, you can load whatever you like on there.
for sheet goods like full-sheet buildng materials, that *would* be pretty wide, something like a five-foot-wide trike, to give about four feet minimum between the wheels.
with a deck over the wheels, you'd still end up with a fairly wide trike: at least a four-foot-wide deck to fully support the sheet goods, or pallet-sized pre-containered loads. and it would still have to be a very long cargo area, about 8 feet long for building-material-type sheet goods. it dosen't have to be that long or wide if you don't need to fully support the cargo, of course, but if you have fragile stuff like sheetrock and must ride quickly on rough terrain, it has to be fully supported to ensure no cracking from flexing. (this could be done with a thick sheet of plywood or a thin sheet and a wood or metal frame under it, that is a temporary enlarged bed, just for hauling those specific items, secured to the actual cargo deck only when you need to use it, and left off completely when not).
on my present trailer with a deck hung below the axles by several inches, the sheet goods and other wide items like empty pallets have simply been hauled on their edges, tied down to vertical support triangles bolted to the deck frame. (essentially doing what the big carts at lowes/homedepot allow for manual transport from store to vehicle in the parking lot).
for the future version, if i ever need it, it would be a six foot wide unit, with duallie independent wheels on each side that takes nearly a foot of width, and a four foot wide deck between them, eight or nine feet long to fully accomodate sheet materials or two full pallets of stuff.
fwiw, one other advantage of having the deck hung between the wheels is that even with 26" wheels, the deck is still only a handspan or so (7-8") above the road, so it is very stable even with at least 4-foot-tall stuff tied down to it (liek vertical sheets, or the piano), and does not have any way to tip over.
a deck that is above 20" wheels with normal tires is a minimum of 21-22" over the road, and will be more than two feet above the road, up to two and a half, with really fat tires, and even more with suspension (because you have to have space for the suspension travel). this, plus it likely being narrower track width, will mean it is potentially prone to tipping under adverse conditions.
A raised cargo bed also gives the option of a bit of space underneath for battery storage.
if you build a cargo box under the seat like i did on my trikes, you can use that for battery, small cargo, etc. others have done this on othe trikes, including tadpole kmx's. iirc i have more than three cubic feet in sb cruiser's cargo box, and closer to 5 or six on the raine trike.
a consideration based on my experiences with both normal riding (desert city) and flash floods:
for battery storage (or other electrical) under the deck is it must be completely waterproof, or any puddles you splash thru will get water inside it. if you end up in a flash flood or have to ride thru deep enough water to submerge it for any length of time, it will get a lot of water inside it. alternately it could have extreme drainage and something like heaters/fans to force moisture out when it does get inside.
fwiw, i had been about to put my battery under the trike when i experienced the first flash flood on my commute home, and ended up in water over a foot deep (probably closer to two). if i had built the battery under there the way i had planned, it would have been completely drowned. i don't know if it would have damaged it but i suspect that long term the water ingress in between cells and interconnects would have corroded things, even if i dried it all out as well as possible as soon as i got home.
so i never did put it under the deck as planned, as i havent' been able to build a guaranteed-waterproof casing for them, that i can be *sure* will not ever be able to leak, but is easy to open for observation and servicing if required. i have ideas...but not yet able to implement them.
