recumbent trike conversion

[Charlie_R]

Long time lurker, first time posting.

A couple of years ago, I built an Atomic Zombie Loderunner. I'm wanting to convert it from pedal only to electric assist.

I've been given a Unite MY1016 250W 24/36V motor, and will be wanting to add it to the trike. I do have a cheap e-bay 36V controller.

What I'm having difficulty with is the reduction gear set. On hand, I have the 10T sprocket (#25 chain) on the motor, and a 65T with freewheel. I'm planning on driving the trike through the mid drive I've been using for pedal power, a much needed accessory due to the hills I have to ride with fairly heavy loads (200+ lbs of me, and anywhere from 60-100 lbs of papers) Trike currently weighs about 85 lbs.

Right now, my budget doesn't allow for LiPo or better batteries, so I'm sort of stuck with SLA. I have three 12V 10AH batteries, and will be ordering 3 more of the same for a 3S2P set. From doing some reading hear and elsewhere, I have the impression that at best I can expect about half the Ah rating to be usable from SLA, unless I want to kill the batteries by overdischarge.

I have the motor bolted down on a test rig, and have been doing a few electrical measurements. So far, I haven't been able to stall the motor, and max current draw has been around 16A. No load draw is lower than the spec sheet says, at 0.8A. Supposed to be double that, no load.

The question I have is how do I figure out if I need to go with a double reduction gearset, or if the 10T:65T will be enough.

 

[Charlie_R]

Today I will be trying a few things with the test rig.

I have, from a failed build of this trike, a pair of wheels still on their axles. I'll set one of these up with the motor, and check the speed of the wheel and see if I can stall the motor.

This being my first foray into electric vehicles, and being on a very limited budget, I'm at a loss on how to best proceed.

I'm definitely not in the same class as recumpence. I love his builds! I'm just trying to add some assist for my work trike.

 

[Geebee]

You will need much more reduction than 10 to 65 if you are going to run it through the pedals as it will still be doing over 500 rpm, a comfortable pedalling cadence would be closer to 60~70 rpm, so a second stage of the same ratios would get you close to 80 rpm assuming you are not over volting a 24volt version of the motor.

 

[Charlie_R]

You will need much more reduction than 10 to 65 if you are going to run it through the pedals as it will still be doing over 500 rpm, a comfortable pedalling cadence would be closer to 60~70 rpm, so a second stage of the same ratios would get you close to 80 rpm assuming you are not over volting a 24volt version of the motor.

Thanks for that!

Messing with the test rig, I came up with a speed of 52 mph using a cheap bike speedo with just the 10:65. Way too fast. So yes, I'll be using double reduction gearing. I think that a 16:90 will bring it down enough, as it is feeding into a mid drive. Mid drive output will be determined based on the results of further testing.

The person that gave me the motor claims it came out of a razor scooter. While the label says 24V, a short search hints that it may be a 36V that was undervolted for that application. A small part of the visible label is torn, and there is what appears to be a second label under it as well. Maybe a replacement motor? I don't know, and not sure I'd care. What is important to me is that it works.

 

[Charlie_R]

I've been doing quite a bit more reading about mid drive style electric assist, and have come to the conclusion that this MY1016 motor will be a temporary solution. Seeing many threads here on the use of hub motors in a mid drive shows me that this may be the way to go.

When I am able, it shouldn't need much modification to change over from current workings to a better system. Just a little rework of the mounting, gearing, and much better motor and controller.

For those who are interested, here are a few pics:

1. This is what I'm working with. I have had to modify the original trike to handle the loads I put on it, not the least of which is me.



2. My "test rig", motor has an 11T sprocket on it, and I'm thinking on finding a 15T better for it. The driven is the 90T I had on hand. The wheel is a 26" from my first attempt on the trike, with 5/8" axle. Yes, I make my own adapters.



3. Test rig with the 65T on a freewheel. Chain is slack because I set this up just for the pics this morning. When I was actually testing, I had the motor placed back further.




Will I need to use a chain tensioner for this stage of reduction gearing, or will slots for the motor mount be sufficient with an adjustment bolt? I'll probably need one for the second stage, as it will have a longer chain between the sprockets and won't have the option of sliding adjustment.

Current option on power is the SLA, but I am really wanting to go with LiPo. Is it possible to buy just a few cells/small packs at a time and not have them go bad while I purchase enough for a decent Ah rating on the final pack?

 

[Geebee]

The motor slots should be fine for a single stage reduction, but if you are going to run it as an mid drive it will need both reductions (2 stage) to get the rpms down to around 80 rpm.

 

[Charlie_R]

I'm waiting on a couple of sprockets, should be here by next weekend. I will then be able to get the second reduction set up with the mid drive. This looks also to be a precursor to being able to go to a better motor.

I still need to know if any LiPo chemistries would stand up to my low budget constraint of being able to buy only a couple of cells at a time, and not have them be worthless by the time I can put together a 20-30Ah pack. I'm still reading up on protected cells vs going with non protected and using a BMS. Or is the BMS going to be needed even with protected cells?

 

[Charlie_R]

Here are a few more pics of the slow progress on the trike:

The seat is temporary, just for getting clearances right for legs, cranks and so forth. I've had to lose the under seat steering, and will be putting together the over seat remote steering later.



The front part of the base plate may get cut off, or I may keep it as additional battery space. Planning on cutting a slot for the output of this stage, and attaching the mid drive above and forward of the stage 1 reduction. Adjustment of stage 2 will be done with the bearing mount bolts. The long axle will be cut quite a bit shorter, and the left side bearing probably moved inboard closer to the stage 1 out when I get the sprockets.



Behind the seat is where I'm planning on putting the first set of batteries, 6 total here. If I need to add more Wh capacity, I can place a couple on top of the forward boom, and one underneath on the front of the reduction plate.



Adding the motor mount plate has also given a side benefit. Frame flex had been reduced.

 

[amberwolf]

You might look up my treadmill motor reduction setup I was going to use on CrazyBike2 originally. There is a little bit about it in hte first page(s) of my CB2 thread here on ES, but a lot more over on my old http://electricle.blogspot.com pages from before I joined ES.


I also had one of those little Unites, but burned it up n pre-CB2 experiments because i didn't use sufficient reduction, mostly.


As for buying RC LiPo a little at a time: Why? Why not just wait till you have enough money and buy all you need at one time? It'd be more likely to be from the same batch(es), and be more likley to have the same characteristics and match closer to each other. Plus its more likely to all have about hte same lifespan as each other.

And also, if for some reason (before you buy them) you change your mind about power source or project or whatever, you'd still have all your money to spend on something else.

 

[Charlie_R]

Ok, as you suggest, I have started a savings program to convert to LiPo batteries.

I do have a bit of a question about hooking up the s-p set. 36V controller, 3s 12V SLA current power source. Fully charged, this pack shows 40.2V. Controller accepts this just fine. When I order the LiPo, do I shoot for close to this for fully charged cells? Like a pair of 4s and a 3s pack for 40.7V fully charged, then parallel as many sets of these as needed to make up the Ah I require? In short, what should my fully charged target be, and then the safe discharge cut-off?

Yes, I do want to add a CA or something similar to the power circuit to ensure I don't go up in a ball of flame, or destroy the investment in these packs.

Amberwolf, you know what it is like being on an extremely limited budget, so you do know where I'm at.

I do have a 90V treadmill motor, but that thing is extremely heavy. Guesstimate is about 70 lbs. Not sure I'd like to try undervolting that at even 60V for use on the trike.

Edit:

I took the treadmill motor out to my work area, and checked it on 36V. Yes it turns, but not much torque at that V. Took the flywheel off, and that seems to be where 75% of the motor weight comes from. Still, it's a heavy motor. I'll keep it in mind for possible future use at closer to it's rated voltage. One problem with it is that it's an open ended case, not designed for outdoor use. The cooling fan for it is integral to the flywheel, so I'd have to come up with another method to keep cooling airflow through the motor. I'm not sure if it has bearings or bushings, as I haven't taken it apart to find out. Bushings would be a non-starter for use on the trike.

 

[amberwolf]

I do have a bit of a question about hooking up the s-p set. 36V controller, 3s 12V SLA current power source. Fully charged, this pack shows 40.2V. Controller accepts this just fine. When I order the LiPo, do I shoot for close to this for fully charged cells? Like a pair of 4s and a 3s pack for 40.7V fully charged, then parallel as many sets of these as needed to make up the Ah I require? In short, what should my fully charged target be, and then the safe discharge cut-off?

That's something you probably want to go look at the "LiPo for Noobs" thread (should be a sticky in the Battery subforum). I only charge mine up to 4.10V/cell, using the "LiIo" setting on the charger when doing it from the RC charger, and I believe my bulk charger is is set to a pack voltage that comes ou to 4.15V/cell.

Some charge to 4.20V/cell; I don't see that it gets me that much extra energy and theoretically they could last longer if not charged as high (dunno if it's true as I havent' done the test).

As for the top voltage (HVC) of the pack, number of cells in series, then yes the best to shoot for is making sure it's no higher than whatever the max voltage of your controller is, and that it's LVC (empty voltage) is the same as the controller's lowest possible voltage (because it's nice to have a safety where the controller cuts out before the pack is truly totally dead empty, just in case).

However, if you want the best performance, pick your pack size so that it's "nominal" voltage (~3.7v/cell) is at the point where it generates the typical speed you would want to ride at, so you have that speed available for the longest time. Doing this means it will have a higher possible top speed for a short while until it "burns off" the votlage between there and fully charged, each time yo charge it up. Just still make sure that you don't exceed your controller's upper voltage limit, to avoid damage.

Yes, I do want to add a CA or something similar to the power circuit to ensure I don't go up in a ball of flame, or destroy the investment in these packs.

Amberwolf, you know what it is like being on an extremely limited budget, so you do know where I'm at.

Yes, yes I do.

One thing to avoid the flames thing is to make sure you test all your packs before you use them, the first time, and to check them for balance periodically as well, at least at first. Never charge when you arent' there to watch for the whole time, either. If possible, package them in a metal box with a controlled vent so stuff don't get in there but pressure from fire could pop the vent instead fo the box. Lots of ways ot do that. (see my Ammocan pack thread for one way; there's a number of others. Dogman has some info about that too, probably in one of his build threads, maybe in a LiPo thread. )

I do have a 90V treadmill motor, but that thing is extremely heavy. Guesstimate is about 70 lbs. Not sure I'd like to try undervolting that at even 60V for use on the trike.

Edit:

I took the treadmill motor out to my work area, and checked it on 36V. Yes it turns, but not much torque at that V. Took the flywheel off, and that seems to be where 75% of the motor weight comes from. Still, it's a heavy motor. I'll keep it in mind for possible future use at closer to it's rated voltage. One problem with it is that it's an open ended case, not designed for outdoor use. The cooling fan for it is integral to the flywheel, so I'd have to come up with another method to keep cooling airflow through the motor. I'm not sure if it has bearings or bushings, as I haven't taken it apart to find out. Bushings would be a non-starter for use on the trike.

Yeah, most likely it has bearings. See my http://electricle.blogspot.com for solutions to the fan problem. But your mtor sounds much heavier than the one I tried to use--more like the other one I have in a working treadmill.

The main reason I was going to use one, was that I had it, and it was a better motor than anything else I had around at the time. Then I got hte powerchair motors, and voila! I had a really torquey solution with low speed output, easily mounted, easy to attach to sprockets, etc. Not exactly efficient, but they did work (powerful enough at 36V (vs 24v design) that they destroyed a number of chains, chainrings, wheels, bent frame bits, etc. while I was experimenting).


If you have to go buy a motor, a Direct Drive type hubmotor is probably your best bet--a rear type so you can put a sprocket on it easily, like Rassy did with his trike, is a cheap way of doing it.