We used 2x4500s (4s) zippy lipos in series, they wern't fully charged I think
Adam said they were around 50%-giving us around 15 volts each so
a total of 30 volts.
What was your optimum set up for the Radio control Katch giving
you the best results?.
I used Dx6i with Receiver ar610 I think ..
Left stick Forward back - Speed / ( Receiver throttle)
Right stock Left right mix - Combines motors tank steer ( Receiver Aylerones )
After my first install ( more luck thank judgement) I trialled out the other channels and I didn't get full throttle... but I've never read the manual for dx6i so I could have potential fixed it I just played to see if there was a better combination. Just a suggestion as possible contributor..
I'm testing mine with 12v x 2 and 12v x 3 24v/36v - 200 kilos this weekend. ( bot & 100kg ) so we'll see what happens or breaks.
Only things that affect yours differently to mine that I can see...... may be useful or you can just ignore me
- Chain friction - dry chain is up to 6 - 9% power loss on motorcycles, Using motul wet road lube is by far the best, almost no fling or mess.. so on smaller power sources is a huge power drain. They over heat and snap or get a lot stiffer a they warm up, they also stretch super quick when dry as in 1 inch in a single short ride. Always spray the inside of a chain so centrifugal force push it into the chain where it needs lubing. If I need a chin drive i'll be using 428 O-ring - no stretch no maintenance in comparison. Grease is retained inside the chain so almost never stretch how we use it. Not much heavier.
- Batteries can produce volts with low amps its like a tidal wave - it can read 15v and have 1 amp behind it. You need a lot more than 1 amp ..I've had plenty of arguments with workshop customers, where they claim a battery is NOT at fault as its 6 months old, but we have load tested it and showing 13.5v but fails loads test, barely enough power to light a bulb.
I would try it fully charged
- Your wiring is half the thickness of mine. reduce draw ? not sure .. I have ZERO bullet connectors all big red things
- Your motors are they used ? 24v ? MY used ones are notably slower than my new ones.. worn brushes or bearings
- Gearing combinations, I don't work stuff out I learn and play with trial an error, but...
I see you used a DID motorcycle chain etc - not sure where but... for reference and guiding you.. you can offer it up against your sprockets..
Example Aprilia rs50 - 12 52mm - 47 225mm ratio is 3.92 for a 12bhp motorcycle that weighs around 100 kilos.
So your 24v motors are being expected to work just as hard ( with internal gearbox ) without the benefit of a gearbox, but move the same weight.
Dropping to 10 tooth front -47 Rear is 4.70 - significant acceleration benefits and much faster movement since we operate at sub 10 mph I would go to 8 tooth front if I could.
food for thought.........
Last edited by katch; 29th January 2018 at 10:05.
We tested it with all the dip switches set to 0. Which is mixed RC input mode, with exponential & MCU modes disabled.
I wonder if it'll get better performance on independent mode instead of mixed.
When I purchased the batteries, I did test that they were able to draw their maximum currents. Which is 202A (45C, 4500mAh, 45 x 4.5). Using a load tester, i achieved satisfactory amounts near to that, however I no longer have the tester to measure an exact output amperage to retest with now.
The main issues I see are the size of wheels, the tyre compound and the gear-ratio. The tyres look very hard and plastic-y, so they probably won't offer much grip. May be worth running a layer of bike tyre around them to improve grip. The wheels are also very close together, which will make turning difficult. The gear ratio from the motor doesn't look that large for the size of wheel so torque may also be an issue.
Obviously changing the gear ratio would be extensive work so maybe try screwing some bike tyre onto the wheels first to see if that improves things. Halfords often have old tyres in the back from bike services that can be obtained for free.
You have hit the nail on the head Jamie-very perseptive analysis from
just a set of pictures.
We do have wheel spin and one factor is probably the hard rubber on
the wheels and also the tread.
Another factor is that the Robot is very front heavy and thus the
weight over the back wheels is too light.
The sprocket ratio is around 4 to 1 and altering this is possible
but as you deduce -not an easy task.
The distance between the wheels will have to remain-it would be easier
to cut off the front jaws and have a lightweight heavy than to alter the
wheel spacing.
Conclusion-Fixable
Yeah. That is definitely an issue we had on sunday. It was slipping on the surface we used, although we weren't able to fully decide if it was due to the wet and slippery surface, or an issue a little bit more sinister at the time. But in hindsight, Jamie is probably correct.
Weight wise, we are already probably within 5-15kg of the limit, so we can't do too much extra, unless we take stuff off. I wonder if we could weld a slab of something between the wheels, to weigh them down a little and give them extra traction.
If I recall correctly, the current wheels are wheel barrow wheels, the type that don't have air in them.
Last edited by Redirect Left; 30th January 2018 at 17:46.
Another week into 2018, another weekend of building!
Before today however, Colin had spent some time with an angle grinder, retreading the tyres. They almost look like they could have always had that tread!
We started today by weighing everything, as for the past few Sundays both myself & Colin have starting voicing concerns over the overall weight of everything, so we brought out the scales, piled everything onto it, and we are up to within 5kg of the weight limit at this point.
Next, we discussed our options for the concerns raised during the motor testing last weekend, which were somewhat disappointing. Two options were discussed, we can either get some extra sprockets in the mix, and increase the ratio from 4:1 to 8:1. There is a potential issue here though, as there isn't enough space at both sides needed for this, the right hand side would fit correctly, but the left would go over to where the jaw control sprocket, chain/belt and motor is. Whilst there is space in other places to do the same but in a different place, so it might end up a bit of a jigsaw puzzle inside. Another option, is using friction drive. There is just enough room on both side to do this, without having to jiggle things about or place things in mismatched locations at each side, we reckon. Later this week, Colin is expecting a large box of sprockets, bushes and other similar items. So next Sunday we'll take a look in there and see if there is anything in there to sway our decision.
A large portion of the day was also spent drilling out holes in the scoop and jaws, after realising we may need to add extra weight as part of the drive changes, even if we don't end up going that way, the less weight will perhaps afford us more armour in areas where needed. The holes have been drilled strategically, in places where it won't cause weaknesses, such as in the jaws themselves, which will usually be within the scoop anyway.
We ended the day by testing out the motors, but removing the ESC from the equation. The roughly 50% charge LiPos were quick to spin up the wheels, although they still skidded on their new treads. The first thing we'll do next week is probably repeat the test with the ESC, and slowly increase the speed to see if we get any better control, and if with a controlled acceleration the new treads will prevent major slips. What we find in Colins box of stuff and how that test goes will take us in the future direction for the bots drive.
Some images from today;
1) The new tread on the tyres
2 & 3) The cut holes in the jaws
4) The holes on the outside of the jaw
IMG_20180204_123549.jpgIMG_20180204_143001.jpgIMG_20180204_145206.jpgIMG_20180204_123435.jpg
Last edited by Redirect Left; 4th February 2018 at 18:22.
BRRRRR-it's been a raw day with a freezing wind but the build continues.
First task was to test the drive system via the speed controller to see
if the wheel spin problem is better with a gradual power increase,
So we set too wiring up the motors and the speed controller and the
radio control-this seemed to take quite a while, I think mainly because
the wiring circuit is not so much plug and play its more screw,zip ties
and gaffa tape-but we are working on the correct wires and connections
for this and the final version should take 5 or 10 minytes tops to
connect.
Anyroad we tried the Robot with the RC gear and although it managed
to bust the door again the performance was sluggish and some wheel spin
still occured so reluctantly we need to modify the gear ratio.
After removing the speed controller we began work on a idler sprocket with
a 2 to 1 ratio, this was in the form of a stub axle type shaft supporting
a couple of sprockets on a brass bush-fabrication went really well until
I realised that the axle shaft had been made too short and didn't allow
for the second smaller sprocket-this was a real set back but after I had
taken Adam to the bus stop I was able to rectify the mistake and I'm
just awaiting sprocket size confirmation to finish the lathe work.
Furthermore to Colins post, I have a few images, and a little extra to add. First thing tomorrow, I will go to a local to me dealer of transmission materials which myself & Colin have used a few times now, Calda-Morley. Due to their fast turn around, we should have the new sprockets for next Sunday easily. Then I can pass on the information of the bore size to Colin as noted in previous post so the shaft can be adjusted if and as required. I've also got some different fuses to the currently installed ones too, as our newer ESC tops out at 60A per channel with a higher margin for short bursts of time, so we're going to replace the current motor fuses to ones of that value, as the motors we use shouldn't top 60A even for a burst. We still have another fuse between the batteries and {the rest of the electrics}, this is currently 200A, inline with the batteries maximum draw of 202A - despite all of the electrical components not drawing anywhere near 200A combined, I thought it'd still be better to give the option to draw more, up to the battery maximum rather than risk fusing what is essentially our master fuse for the entire bot.
Some images from today.
Securing our Zippy batteries with some Zippy ties!
IMG_20180211_130040.jpg
For the second consecutive weekend, we managed to break the workshop door.
IMG_20180211_132140.jpg
This week we worked on the sprockets to increase the ratio for
the drive from 4 to 1 to 8 to 1 overall.
I had been working on the problem in my mind all week and with a
couple of failed practical experiments with bearings I had settled
on a wheelbarrow style bush/spindle support system.
Adam had ordered 2 new sprockets from calda morley with a bore
size of 12mm but when we looked at the sprockets they were much
smaller than the 12mm required so they needed work first off.
Earlier in the morning before this I had turned down the spindle to
support the 2 sprockets one of which I bought online and welded on
this onto the spindle.
One of the sprockets that Adam had brought was drilled out to fit the
spindle too and we had our 2 to 1 ratio-giving us 8 to 1 overall.
We had made one support bracket last week which needed slight modification
by means of a bush and housing welding to it and a second smaller version
bracket was made with bush/housing for the other side also.
This all seemed good and with the sprocket between the brackets it
seemed to line up well with the wheel and the motor sprockets.
There was a slight stiffness on the spindle in the bush but I narrowed this down
to the end cap of the spindle and I gave this a skim on the lathe after taking
Adam to the bus stop and it was a lot better.
I should be able to fit the chains beofre Adam comes over again and we can
see what difference these changes make.
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