Motor woes… And tantrum throws.

We do this because we love it.

We do this because we love it.

We do this because we love it.

(Keep repeating the mantra)

It’s not that bad, but some parts of the process can make you swear a little. Additionally, it’s 48hrs to the Pi Party, I’ve got loads of prep left to do – and have had lovely tonsillitis for 3 days. Seriously hoping the antibiotics kick in soon!

So – four motors right, just four little motors. No problems. So, I started ordering motors back in November and after two hopeless ebay sellers took TEN WEEKS to fail to deliver anything to me at all I was getting a little sweaty by the time the new year crawled round. So, third time’s a charm (as the saying goes) and I found another supplier who actually delivered the goods in about a week.

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Last year’s motors at the front – new ones behind. Ooooh – look at the shiny shiny!

I was sooooo happy to get my hands on these then a few things started to dawn on me. The motors are 12v. I am using a ZeroBorg from PiBorg, the very neat little 4-channel controller they first launched as a Kickstarter campaign. Turns out the ZeroBorg can only take a maximum of 10.4v, so I am actually running it at 9v. Bang goes 25% of the power going to the motors immediately.

In addition to this, the motors are rated as ‘300rpm’ (when running at 12v) So I expected around 200-225rpm at 9v. This I would have been happy with. The motors I used last year were 130rpm but really torque-y. These new ones actually turned out to run SLOWER?!! Whoever gave these their speed rating needs a good talking to IMHO!

Back to square one.

Another year, another supplier (Ireland this time)….

‘Hi, you have 300rpm, 6v motors?’

‘Yes’

‘And they’re definitely 300rpm?’

‘Oh, yes’

‘And they’re definitely 6v?’

‘Oh, definitely sir’

Fantastic. So, I order and a week goes by. I am juuuust getting antsy when a parcel lands on my door step.

Containing three motors.

And a note ‘Sorry – we’ve only got 3 of those atm, we’ll send you the other on back order when we get it – possibly by March.’

Calvin-Facepalm

Are. You. Kidding me.

(Oh – it’s now March, and I am still waiting.)

So, I find my FIFTH supplier, in the US this time, who has the exact same motors that I have three of, but at a premium price plus US / UK shipping costs. I therefore spent a lot more than I should to get a matching forth motor. In fairness to the seller, he shipped immediately and it arrived within a week.

And guess what? – The SAME motor, from the SAME manufacturer, with the SAME label actually has a 6mm shaft not a 4mm as the others do. And it runs significantly slower than the other three. Utterly frustrating, but can’t really blame the seller for that one, although QC at this particular manufacturer obviously leaves a lot to be desired!

So, with 6 weeks to the competition, I am yet to find a fully matching set of motors. I have compensated in the code to allow for this, but it does mean slowing the other three down to match which isn’t really great – I certainly won’t be winning any speed runs I feel!

One a positive note, I’ve designed my own motor mounts for standard 25mm gearmotors, I’ll put these on Thingiverse so they’re available. Very pleased with the way they turned out…

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I’ve also got the Pi Zero / ZeroBorg wired up and have started tweaking the code. I’ve also got a PS3 controller set up for manual challenges. This is a significant step up in usability and complexity from last time round. Think I’m also going to need a lot more driving practice!

 

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Next time…. Get it together, man. – Time to get chassis-tastic and try and actually build a bot!

Until then…

DP.

 

 

 

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