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  #61  
Old 02-10-2020, 09:19 AM
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Quote:
Originally Posted by Bgt2u View Post
Hi there, it seems like you are building something along the lines of what l have built. I can go into detail of what l used, and how it was accompanied, if you would like. My hight speed power chair tops out at 35mph, and has a range of about 5 miles.
That is magnificent!

Please do post full details and more pictures of your rover.

I would love to read all the details, why you did this and that, how it has worked out, and what you might do differently next time.

Your machine is like something NASA would design while mine is like a farm boy design.
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Old 02-10-2020, 11:40 AM
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Thank you! Lol, l do appreciate the compliment. I am a retired Electro/Mechanical/Structural Engineer, so that might have given me a slight advantage. When, l have time, l will provide more details, and pictures. I basically built this on the same premise that you built yours, only l made it for myself. I am disabled, and have a Hoveround power chair, that clearly has it's limits, and refuses to do much of anything outdoors. I like to putt around town, other than in my car, so, l figured.....l'll just make my own offroad capable high speed piwerchair. Right now, it is patent pending, and l plan to sell them to disabled people, kids, or whomever just wants one. Believe it or not, l actually get stopped all of the time, with compliments, and questions. Bye the way, l am impressed with your "farm boy" design. Good job!
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  #63  
Old 02-11-2020, 02:07 PM
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I do believe people stop you and want to learn about it!
Patent pending is really something so I hope it works out well.
You have a huge advantage with your training and experience, and that is why your design came out so well. As a user, you understand what others will want in a power chair.

I look forward to reading all about it, soon I hope!
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  #64  
Old 02-11-2020, 02:21 PM
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Default Shaping

Last night I only had a little time but I did get the foam "hood" area shaped and ready to be glassed.

Before:
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After roughing the curve with a belt sander:
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After hand sanding:

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Next up is covering the foam and then primer... paint... more paint... etc.
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  #65  
Old 02-11-2020, 10:39 PM
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Nice work on the hood!!
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  #66  
Old 02-14-2020, 02:53 PM
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Default Minor progress

I had half an hour last night so I "glassed" the hood, with out fiberglass.

Have you read about PMF?
That stands for Poor Mans Fiberglass where they use various fabrics and various liquids to coat objects prior to painting them.

People use old Tee shirts, new cotton roll fabrics, canvas drop cloths, and just about any fabric, woven or not.

Then they coat it, and saturate it with paint, varnish, glue, resin, or whatever they have on hand to try that will dry and hopefully glue the fabric on and harden up.

I have some epoxy left over from other projects so I mixed a bit of it up...

And covered this:

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With two layers of fabric:

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And this is the fabric I used:

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Tonight I will trim off the excess and see how well the fabric worked.

I have about 275 ft(!) of 42" wide 4 oz fiberglass cloth left on the roll I bought a few years ago but it is up high on a shelf that requires ladder access and it is heavy. If the PMF isn't good enough I will climb up and get it down to cut off a little piece to bond over the weed fabric.

Or maybe I should see what cotton cloth Robyn has in her sewing room that she has no plans for?

All good fun, eh?
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  #67  
Old 02-19-2020, 08:31 AM
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Default Paint!

First coat of paint is on

Primer:

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Flat black undercoat:

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Desert Sand (Flat) body color:

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Front end set in place to see how it is going to look:

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I put one of the headlight reflectors in place (not installed) to see if I like it. I think I will use them. They will be centered in the cutout.

More coats of paint to put on and the grill will be glued on (it is just hanging on one nail in the picture) before final installation of the body.
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  #68  
Old 02-19-2020, 11:24 AM
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Love it!! Great job
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  #69  
Old 02-19-2020, 07:30 PM
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looking awesome!
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  #70  
Old 02-20-2020, 06:14 AM
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Awesome build so far..

I think the box now needs some cosmetics to make it
"theme match" the jeep body
(say a safari luggage rack decal )

And I'm sorry to warm that up but I have to:
Quote:
Originally Posted by Functional Artist View Post
It looks like you got (2) 24V 4AH batteries, wired in series, to form (1) 48V 4AH battery pack

...to power a 48V 1,800W motor that draws IIRC ~40A

A 48V 4AH battery pack can supply 4A for (1) hour
...or ~8A for 1/2 hour (~30 min.)
...or ~16A for 1/4 hour (~15 min.)
...or ~32A for ~7.5 min.
& then, there's probably gonna be some Voltage drop/sag too
That's is a perfectly valid concern.
If you need 40Amps, 4Ah are not going to last very long

whereas that response to it:
Quote:
Originally Posted by Quinc View Post
Different animal compared to lead.
is a complete and utter BS I'm afraid,

battery capacitance and current demand
as calculated by Kevin above have absolutely ZERO to do with
battery technology.

I know lead acids cut off sooner than Lipos do on the same occasion;
and so does Kevin for sure;
but the controller doesn't know what battery is connected.
and most cut off sooner than a lead acid would anyways in order to keep those safe and rechargeable.
And in fact:
none of that is (or needed to be) part of the simple x/y=z equation from Kevin above

If you flush your loo with 40 gallons per minute and
have a four gallon tank, it doesn't matter if that tank is ceramic or plastic or steel,
it's empty in six seconds.. period!

I think I know what actually happened here,
namely your ride was still far away from full power
(and don't get me wrong, that's perfect!)

If the motor never needed anything like 1800W even under full throttle, then it just wasn't drawing 40'ish amps.. but maybe only half of that.
makes me wonder.. have you set the speed limiter perhaps?
which on those controllers is actually a throttle divider,
(usually throttle signal will be cut in half for mid and in third for slow speed)
since that results in cut in half/third power
(PWM is 50% duty cycle peak power doesn't change.. available power does.. nevermind)
and 16 amps max for ten minutes
and 10 minutes of maybe 4 Amps
results 3.3Ah of capacitance used
in twenty minutes... sounds plausible to me looking at your results ...
Quote:
Originally Posted by JagLite View Post
I rode it for twenty minutes almost continuously and at full throttle most of the time.
The battery monitor had me at 25% for the last five minutes and the top speed dropped by half in medium range but stayed the same in low range at 5 mph GPS speed.

I forgot to check the top speed in medium before the battery dropped to 25% so the fastest recorded was 7 mph.
with 7mph top speed there isn't much acceleration going on (which causes the highest demand)
and even under full throttle 7mph isn't requiring anything like 900Watts;
maybe in the realms of 350-400 Watts max.
So mid speed setting wasn't even maxed out really.

I think just cruising would take you about 200Watts on your kart
I think you can (on level road) get a cruising runtime of
about'ish 45minutes or so from your 4Ah batteries.
if you can tell me what that mobscooter weighs with you on it..
I can get you a better guesstimation
or you can calculate it yourself from this

Anyways;
I'd too suggest to stack a pair of backup cells into the trunk
to swap them out in case you need a bit more oomph and thus greatly reduced the mileage (say climbing an inclination)
just in case.

Since after all, at worst that motor will draw almost 40Amps
and even a 4Ah LiPo pack will not be fully drainable
and only provide you with maybe 3.5-3.7AH of useable capacitance.
So at worst that battery is empty within five to six minutes of full power,
if the controller doesn't cut out earlier that is

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  #71  
Old 02-20-2020, 09:29 AM
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Thanks Sid, the controller does have the three levels of power and I have a switch to choose between low and medium. My dad will most likely only use low and he says 5 mph is just right.

That may change as he gets used to it of course, but the gearing should keep it slow for safety.

The Jeep weighs 175 Lbs and Dad weighs 185 Lbs so the total will be about 360 Lbs for the little motor to haul around. He will use it on mostly level ground and just cruising along.

I am sure you are correct that we are only use a small amount of what the motor is capable of so that will help a lot with battery life.

We are planning to buy another pair of batteries to keep in the storage box. After finding out how long/how far the 4AH batteries last we will get either the 2AH, 4AH, or 6AH pair.

Dad thinks that maybe he will use it twice a day (on sunny days) to ride two blocks to the lake and sit there to watch the kids and rowers for a while before riding back home, making the trip in the morning and in the afternoon. I just want him to have plenty of reserve to get home.
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  #72  
Old 02-20-2020, 10:16 AM
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I'd dial towards the 6AH pair..
since even if the 4Ah set is sufficient usually..
you will recharge them more often,,
And the number of charging cycles is limited on LiPos (usually around 1000 full cycles)
so in the end, a bigger pack may not physically be needed, but pays off since it just holds years longer

Since Watts are metric... I'll convert to scientifically relevant formats
360lbs are roughly 165kg (rounded up a bit .. a heavy coat in the winter or so)
5mph are a bit less than 2.3 m/s (meters.. )
7mph are a bit more than 3.1 m/s and finally
10 mph are just under 4.5 m/s (yes I'm easing the calculation a bit)

cruising speed requirements on level road
165 kg * 9.81 m/s * 0.02 * X m/s +
0.5 * 1.2 kg/m * 0.7 * 0.9 m * (X m/s)
since we'll reuse that for different speeds
just simplifying that to
32.373 kg m/s * X m/s + 0.378 kg/m * (X m/s)

makes
less than 80 Watts at 5mph (100 W)
less than 120 Watts at 7mph (150 W) and
about 180 Watts at 10mph (225 W)

cruising speed requires less than I thought tbh

and climbing up a ~9% slope
requires ~ 141 Newton (165kg * 9.81 kgm/s * sin(5))
makes (just times speed to get the power)

less than 325 Watts at 5mph (405 W)
less than 440 Watts at 7mph (550 W) and
less than 635 Watts at 10mph (794 W)


black numbers are purely mechanical power...
fair to assume an efficiency of 80% for your motor (maybe a bit better even),
so your powerdraw will be 1.25 times those numbers (added in red)
the occasional stick and stone curb to climb etc left aside.

it's got enough power to provide comfort (even for some advanced grocery shopping)
and still has the power to climb up that nasty curb most of the time.

Nice setup indeed

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  #73  
Old 02-21-2020, 03:06 PM
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Thanks Sid!

The final results you figured out look great to me.

I don't know what that is written in some foreign language though...?

Chinese? Arabic? Hieroglyphics? Atlantian? Numerology? Egyptian?

165 kg * 9.81 m/s * 0.02 * X m/s +
0.5 * 1.2 kg/m * 0.7 * 0.9 m * (X m/s)
since we'll reuse that for different speeds
just simplifying that to
32.373 kg m/s * X m/s + 0.378 kg/m * (X m/s)

As my maths teacher in middle school said:
"There are 3 kinds of people in the world, those who understand math, and those who don't". You can guess which group I am in.

However, since you gave me the answers that I can understand, all is good.

Certainly the 6AH batteries will be the best, they just cost a lot more (2X the 4AH) so we will see how much Dad actually uses his little Jeep.

I put the second coat of paint on the body last night but no pictures, it doesn't look any different...

I asked on another forum (where I have a more detailed build thread) what others think about the storage box. Paint it to match or leave it as is? Or just paint the red top to match and leave the box black?

What say you?
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  #74  
Old 02-21-2020, 08:46 PM
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you're welcome.

Math and Physics (in the realms that we need to deal with around)
is simple really, you only need a few tools up your sleeve
know what dimensions are and what they break into really
like mechanical power Watts are kgm/s
Torque is Newtonmeters or kgm/s
Force is Newton or kgm/s
And you suddenly realise there will never be power without torque
see.. that easy

Judging by the smile on your dad's face while testriding it (love that!)
I'd assume he'll be riding it whenever he get's a chance

But yeah if 6Ah batpacks are twice the price of 4Ah batpacks,
then the manufacturer or retailer is an idiot I'm afraid;
I'd too would rather buy four 4Ah batteries then.

Box..
too bad it's not round, then you could've just disguised it as a spare tyre.
I wasn't kidding ont he luggae rack though..
painting the lid black maybe brown
adding a few lines of aluminium tape (cut into narrower strips)
maybe halfway up the prodruding box to fake the rack
aaand leather strips with buckels as old timey fasteners perhaps *shrugs*

Or you could find some African Safari decals or Camel Trophy.. Ralley paris-dakar or something.. to cover the box in.. weather them properly and it'll look good I bet.

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  #75  
Old 02-24-2020, 09:03 AM
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Easy!

Hahahahahahahahahahaha

Simple, everything is either kgm/s, kgm/s, or kgm/s


Uh, what language is that?


Thanks for your help Sid, but I never had any teaching beyond basic math. I flunked 2nd grade because I couldn't read so I had special ed reading classes and struggled in school to just get "C" grades. It wasn't until long after I was out of school that I realized my memory doesn't work like most people. I have a very difficult time remembering anything. I can't even remember my own phone number and address. I have thing written down because I won't remember...

So much of what we consider intelligence is all memory, the better a persons memory is, the smarter they are. I was invited to join Densa but I forgot to send in the paperwork.

But, back to the project!

Speaking of memory, yesterday I was very good at remembering to take pictures of each step as I worked on it, then last night when I was going to download the pictures to my computer I discovered that the camera memory card was still in the computer... I forgot to put it back in the camera.





But I did get a picture of Dad when he came out to check on progress

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  #76  
Old 02-24-2020, 09:44 AM
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memory is good to have alright..
but intelligence is more about being able to figure things out to solve a problem.

Aaanyways.. there's your happily smiling dad again..
I get a feeling he's still in contact with his inner kid; that's awesome!


beige lid looks much better than the red
Almost inclined to say to leave it at that

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Old 02-24-2020, 12:41 PM
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Exactly!

I can figure things out and solve problems, I just can't remember how I did it later.

I am always pleased when the engineers (here at work) do the calculations on something I have designed and I see how close I was on the steel beam sizes and other structural details. I draw it up in the computer and the boys do the calculations so we are all happy.

I believe I am the only one in our Civil/Structural engineering company (100+ people) who doesn't have a degree. I've only taken one University class and that was one semester to learn how to use AutoCAD.

I am not planning to paint the storage box, I am leaving it black for now at least.

Now I am installing a brush guard on the front, hooking up the longer brake hydraulic line, and bending some sheet metal to cover the front and rear of the floor area.
As well as a dozen small details...
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