Convert 1975 Afron Cherrypicker?

Technical discussion on converting internal combustion to electric
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Adverse Effects
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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Sat, 05 Mar 2011, 07:15

it dont stop you you emailing them asking if thay have a 48 volt 150amp unit

or you could just go here DS162KD01 Rhino 160A Controller with lights or reverse beeper
Last edited by Adverse Effects on Fri, 04 Mar 2011, 20:28, edited 1 time in total.

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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Sun, 06 Mar 2011, 21:53

i was just thinking

you dont need high amps

your running worm drives all you need is high RPM running at 1Kmp/h or running at 20Kmp/h will use about the same amps

this is because of the worm drive

i have seen a range rover(2.5+ ton 4X4) at idle (750 RPM) climb a hill that was over 45deg and it was moving at the same speed as it was on the flat area b4 it and then it came down at the same speed

any motor at idle at makes only a few HP (just enough to keep it spinning)

so your drive shafts will only have a low amount of load on them
Last edited by Adverse Effects on Sun, 06 Mar 2011, 10:57, edited 1 time in total.

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Convert 1975 Afron Cherrypicker?

Post by Trogdor! » Mon, 07 Mar 2011, 02:37

I agree that the torque on the drive shafts should be more or less constant (while travelling on level ground) regardless of speed, however as the RPM on the shafts increase, so will the power required (Power = torque x 2pi x revs per second).

Thus for some target maximum speed, I will need a certain amount of power, so in looking at motors, it's that power figure I'm paying attention to.


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Convert 1975 Afron Cherrypicker?

Post by Electrocycle » Tue, 08 Mar 2011, 03:31

yep, exactly right.

There is no way around it needing X amount of power to move its weight up a certain incline, or over soft ground, etc at a given speed.
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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Thu, 17 Mar 2011, 18:36

Electrocycle wrote: yep, exactly right.

There is no way around it needing X amount of power to move its weight up a certain incline, or over soft ground, etc at a given speed.


my point was he needs to look at RPM first then everything else

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Post by Trogdor! » Thu, 05 May 2011, 21:04

Having appraised the feasibility and cost of the conversion, much of that with the help of the good folk here, I've decided to go ahead with it.

The negotiation with the neighbours who own it went surprisingly well - they decided to give it to me for free on the basis that they can borrow it as needed Image

Better still they've offered me a pile of ex-phone-exchange batteries - they may end up too heavy or inappropriate for mobile use, but for the time being they'll be very handy for getting the thing going. Image

Being the fashionable thing to do, and to help with my rotten memory, I've put up a build log here:
http://e-afron.blogspot.com/

Some pics you've seen in this thread, some more recent as I've started work on the machine.

First off the block, after cutting off some previous modifications to reduce size and weight, is the hydraulics. The blog explains the process of estimating how much power is needed for the boom lift cylinder, and I've bought a 24v 2.2kW power pack off Ebay.

I want to sort out the hydraulic bit before getting on to the wheels as I may want to order a third speed controller in my order from Kelly Controllers to run the hydraulic pack. I'd get a 48v controller so that I can connect it to the main 48v battery pack - this also would give me the option of upping the power from the hydraulic drive if it proves too slow.

Probably the only thing I'm still not sure about is coupling the drive motors to the wheel gearboxes - I'm guessing I'll need an intermediate bearing or two to keep shaft under control, but it's something I don't have much of a clue about. Image
Last edited by Trogdor! on Thu, 05 May 2011, 11:06, edited 1 time in total.

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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Fri, 06 May 2011, 01:06

that is awesome mate

i carnt believe that just gave it to you WOW that is a dam good start

i will be watching this with great interest

and i said it once i'll say it agan i dout you will need as much as 2HP for each wheel   more like 1HP

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Post by Trogdor! » Fri, 06 May 2011, 01:40

They're very nice neighbours, and the machine is pretty old in the tooth - I'd done a fair few repairs to it during the past few months we've had it, and the shaft seals on the gearbox all constantly leak oil, which is going to be a big job.

You may well be right about the power requirements. I did some more torque tests today and think my previous calculations were wrong. To move the machine forward on flat ground it takes between 6-14Nm of torque - if we assume 14Nm, at the 1200rpm shaft speed it equals 1.75kW, or 2.3HP, so a bit over a HP on each side.

But that's on the flat, and that's also with the machine being too slow. If I want it to go 3 times as fast, that's 5.2kW or 7HP, more if going up an incline at speed.

Anyway, eventually I'll find out if it's way overpowered Image

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Post by Electrocycle » Fri, 06 May 2011, 03:30

yep, better to have oversized motors than undersized :)
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Post by Trogdor! » Wed, 11 May 2011, 04:43

I've done some more testing and messing about with the machine. My latest conclusion is that it should only require about 440W to move it at the current speed on level ground:
http://e-afron.blogspot.com/2011/05/how-much-power.html
Not sure what this means in terms of my choice of motors though...

While I ponder that, my hydraulic power pack turned up:
http://e-afron.blogspot.com/2011/05/hyd ... -pack.html

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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Wed, 11 May 2011, 14:55

you could slap 2 of thes babys on
http://www.hobbyking.com/hobbyking/stor ... oduct=5142

main thigs are

Voltage Range: 20-48v
Input Voltage : max. 48V
Kv : 130 rpm/V . . . . . @24VDC you get 3120rpm
Maximum Power: 6500W
Equivalent: 60-80cc Gas Engine
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Convert 1975 Afron Cherrypicker?

Post by Trogdor! » Thu, 12 May 2011, 01:36

http://www.hobbyking.com/hobbyking/stor ... oduct=5142

Damn that looks tempting! Can't argue with the price either. It'd require a bit more control trickery to get it to do skid-steer, as I don't think reversing brushless speed controllers are very common.

The only question I'd have is what kind of behaviour it'd have at low speeds, as you do need a wide range of speed to allow accurate manoeuvring.

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Post by Trogdor! » Fri, 13 May 2011, 04:20

So the power pack has been set up, bench tested, oil spilt everywhere and finally installed in place of the IC-driven pump:
http://e-afron.blogspot.com/2011/05/wir ... ulics.html

In this post you get to see the 60kg deep-cycle batteries the neighbours have donated. Damn they are heavy Image

At the end of the post there's a video showing the boom lift in action, both at 12v and 24v. The difference isn't obvious at first, but at the end of the vid I show 12v versus 24v lift right after each other.

At 24v it lifts to its highest point in 10 seconds, versus 9 seconds for the IC-driven pump, which I think is a pretty decent result.

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Post by Electrocycle » Fri, 13 May 2011, 13:45

sounds like a job well done on the hydraulics :)

The R/C brushless motors are good value for the power they make, but they're not very robust, run at high rpm, and the controllers don't like starting up under load so I don't think they'd be suitable for this application.
You really need to over engineer the drive train for reliability - and it'll take a surprising amount of power to get over bumps and drive up hills.
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Convert 1975 Afron Cherrypicker?

Post by Johny » Fri, 13 May 2011, 15:54

Nice progress!

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Post by Trogdor! » Fri, 13 May 2011, 17:11

My clamp meter turned up today and I finally got a chance to find out how much current is involved. Lifting me on the platform draws 86A at 24v - 2.1kW which is just under the rating of the motor.

Looking about that Hobby City web site it occurred to me that I could probably run the lift quite happily off a 6S 5,000mAH 20C LiPo. The only catch might be the peak current - according to my meter, the 1ms peak was 530A...

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Post by Trogdor! » Fri, 13 May 2011, 17:22

Electrocycle wrote: sounds like a job well done on the hydraulics :)

The R/C brushless motors are good value for the power they make, but they're not very robust, run at high rpm, and the controllers don't like starting up under load so I don't think they'd be suitable for this application.
You really need to over engineer the drive train for reliability - and it'll take a surprising amount of power to get over bumps and drive up hills.


I've been giving this a lot of thought since Adverse Effects pointed out that motor. While on paper it'd most likely do the job quite well, particularly given the low-revving 130KV, it is ultimately designed to spin a prop, meaning it'd need a fair amount of support for the shaft to cope with the much higher torque involved.

Then there's the speed controller. The same bunch do have a car controller that can be configured to work in a skid-steer fashion, but this kind of controller has no current limiting, and is not exactly built to the most robust of standards, as it's ultimately designed for toys.

The reality is that this is a working machine and has to have the rock-solid reliability that you'd expect from the IC version, so I can't afford to have any weak or marginal components, both from a reliability and safety point of view.

For example, if the control electrics fail on the hydraulic lift, you could be stuck 4.5m in the air with pretty much no way of dropping the boom, unless someone works out how to supply power to the right 2 solenoids simultaneously to release the oil back to the tank.

That said, once those motors are back in stock I'll have to grab some just to have a play with them and maybe make up a less critical machine for them Image

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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Fri, 13 May 2011, 19:18

go kart

there has to be heavy duty controllers out there for them look here

thos motors have that much power that the clutch carnt take it and it starts to burn

i have 1 of that type of cutch and its on a 11HP ICE and the only time it gets to hot is on a realy big up hill clime with my 160Kg on it and from a standing start

if i am at speed befor i hit the hill the clutch has no problem and you can allmost touch it at the top of the hill
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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Fri, 13 May 2011, 20:19

then again you could all ways build 2 mini open revolt controllers

or you could go back to one of my prevous posts
DS162KD01 Rhino 160A Controller with lights or reverse beeper
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Post by Trogdor! » Fri, 13 May 2011, 20:44

That kart video is awesome. However the comments highlight the key problem with sensorless motors - they're not suited to starting under load as the controller needs to see back EMF to understand the rotor position, and the other point the guy made is that the controller he's using has no over-current control, hence the clutch.

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Convert 1975 Afron Cherrypicker?

Post by Adverse Effects » Sun, 15 May 2011, 05:20

here is an idear

24 volt truck starter motors?

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Post by Trogdor! » Wed, 18 May 2011, 00:19

I need a bit of advice regarding the electrical side of things:

1. I'm planning on using a 400A contactor, but not sure whether to use a 12v or 48v coil.

2. Does anyone have any ideas about wiring 3 Kelly controllers? Can I connect the signal grounds and use one 5v supply from one unit for the throttle/inputs?

3. I notice the Kelly controllers have an output to drive the main contactor - how would this work if you have three controllers?

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Post by Electrocycle » Wed, 18 May 2011, 03:09

ideal would probably be to run 3 contactors, but shouldn't be necessary.

I'd just run one contactor from one controller.

Whether to use 48v or 12v coil depends on the controller specs. If it just switches battery voltage to the coil you'll want 48v, but it might do PWM so you can use 12v.

Running all the controls from one controller's 5v supply should work ok, but ideally I'd probably run them separately from each controller, in a shielded cable since it'll have a pretty long run.
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Post by Trogdor! » Sat, 28 May 2011, 16:44

Anyone know about coupling motors?

Because of the machine's wheel, the motor can't go right up to the gearbox, rather, to be clear of the motor it'll need to be mounted a bit further away - can I get away with some kind of long coupling, or will I need an intermediate bearing to support the shaft?

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Post by Electrocycle » Sat, 28 May 2011, 23:27

A long shaft should be ok as long as everything is well aligned and mounted.
You could probably use the original universal joints and a section of the original shaft.
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