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Re-boring Keyed Drive Hub - Ideas?

CalgaryPT said:
I've never tried it, but you have me interested. I just assuming it would chatter to heck. I do have some old imperial hubs from PA in a box in the shop. I'll see if I can find them. I don't think they are hardened. I do have boring bars that should do the trick. Any other tips?
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I assume you have this sorted now? Like Kylemp - an interrupted cut in a lathe is not a big deal, whether boring, facing, external - whatever. Obviously take it a bit slower and make about 3 equal spring passes at the end (with a tool you know is sharp). For an 11/16" hole and if you are actually going to target a slip fit then the tolerance won't give you much to play with (as Kitta above points out). Pull up a Limits & Fits chart (SKF has a good one, also Machinery's Handbook) and they spell it out very well.
 
I've been around RC a long time & lots of electric experience. Happy to answer any questions or bounce ideas but I suspect probably 10% of that knowledge is applicable to your project. You are in robotics territory & we are predominantly lithium polymer except for a unusual circumstances. LiPo is preferred for power:weight density, but that probably is not a factor to warrant price. I lost track of how many NiCd & NiMH packs I soldered back in the day. But those were end to end soldered with a hammerhead iron tip. ie no wire, lowest possible resistance. Pulling 200A was not uncommon, sometimes much higher.

Anyways, one thing to check regarding home brew pack building kits. Those strips come in different gauges & it must be sized for amp duty no different than wiring. I'm not sure what amps you will be pulling but I'm sure they are tables. I am curious what kind of inter-cell joining is done on e-bikes & such . Probably expensive but I see there are suppliers like this.
https://www.ebikes.ca/product-info/battery-kits.html
I'm sure the robot suppliers also have off the shelf voltage x maH packs & corresponding chargers. Unless times have changed, its one of those get what you pay for deals. Crappy cells or even crappy QC across numerous cells can be a PITA.
 
PeterT
My ebike is 350W and 36V so normal full load is 10A. I’ve set the controller to max out at 17A. I’m not sure how this works but there is a noticeable difference in performance between it set at 10A and 17A.
The battery is made up of 50 Li-Ion cells. 10 series x 5 parallel. It is a maze of metal strips. Each cell Is directly connected in parallel and in series for a total of upwards of 200 strips. On average each series strips would only carry 2-3 amps. It’s a pretty robust system considering the relatively low Amps. I’m sure the requirements for 200A are a lot more critical.
The charging system is also different than a typical RC charger. My charger is rated at 4 Amps, so less than 50% of full load. Don’t RC chargers have higher ratings? The ebike BMS is not a true balance charge either.
 
Johnwa, its not uncommon to have chargers in the 1500W range, or like 1000W side for simultaneous pack charging.
https://www.progressiverc.com/charging/bench-charging-combos/
But its very much application (power) dependent, planes vs heli's vs.... One of the main differences of RC is pilots want to charge & fly, rinse & repeat all day long. Lipo battery chemistry has high C, meaning it can deliver a high percentage of its nominal capacity. This is improving all the time, 45C is considered average. 90Cs can be purchased in several sizes now. But this (low internal resistance) also means they can be charged at elevated levels. This probably isn't as important for other applications like power tools & of course comes at a price.


A 2m aerobatic model might use twin 5S-5000maH packs. 5S * 4.0v/cell nominal = 40v. Not sure on current levels but guessing 80-100A. These are brushless, typically outrunner motors. Some larger heli's will use 6S. https://www.f3aunlimited.com/powerplant/batteries
 
PeterT said:
I've been around RC a long time & lots of electric experience. Happy to answer any questions or bounce ideas but I suspect probably 10% of that knowledge is applicable to your project. You are in robotics territory & we are predominantly lithium polymer except for a unusual circumstances. LiPo is preferred for power:weight density, but that probably is not a factor to warrant price. I lost track of how many NiCd & NiMH packs I soldered back in the day. But those were end to end soldered with a hammerhead iron tip. ie no wire, lowest possible resistance. Pulling 200A was not uncommon, sometimes much higher.

Anyways, one thing to check regarding home brew pack building kits. Those strips come in different gauges & it must be sized for amp duty no different than wiring. I'm not sure what amps you will be pulling but I'm sure they are tables. I am curious what kind of inter-cell joining is done on e-bikes & such . Probably expensive but I see there are suppliers like this.
https://www.ebikes.ca/product-info/battery-kits.html
I'm sure the robot suppliers also have off the shelf voltage x maH packs & corresponding chargers. Unless times have changed, its one of those get what you pay for deals. Crappy cells or even crappy QC across numerous cells can be a PITA.
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I don't intend to build my own packs for the drive motors; I'm just kinda interested in what you've done. Wheelchair motors typically utilize 2 series 12V lead acid, for a couple of reasons: 1) cost, and 2) the fact that they aren't drained quickly but used in short bursts. Actually most aren't even deep cycle and are like this: https://www.canadiantire.ca/en/pdp/motomaster-12-volt-32ah-group-u1-sla-battery-0102051p.html#srp . My requirements are about 45 mins run time for my lawn.

I will, however, look into building my own packs for the mower motor as this seems a more pressing concern once OEM are unavailable.

And thanks for the help offers as I progress. I may add optical encoders down the road, but one step at a time. I get to do some hydraulic bending for the frame, so am focused on that now.
 
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Deep cycle chemistry is more tolerant & forgiving to ...well.. deeper cycling :) Sometimes they are called RV or Marine, but those are just the more common usage applications. To make it confusing there are marine starting batteries which are just reduced typical lead acid (non deep cycle). DC performance varies by manufacturer & I'm not up to speed on the latest but most should be able to deliver 50-75% of rated capacity, recharge & repeat for life. There is still a price to pay, persistently going deeper means reduced overall cycle life.
https://www.altestore.com/blog/2015/10/understanding-deep-cycle-batteries-part-2/

I'ts sometimes hard to find the recommended discharge C rating of lead acid batteries because its not really a common term like more modern typical 'rechargeable' cells refer to or publish tables. Ideally you can find 'recommended amps' & back calculate. I've always thought 'cranking amps' was a bit salesy & flakey because the duration & frequency is undefined. Anyways simple math: if you have 35 A-hr battery & the recommended max discharge current is 40 amps, then C = 40/35=1.14C. But usually we have a motor or load that dictates current, so we can determine the proper capacity. Say 50A load, so 50*1.14= 57A.hr. Its more complex than this because you can (within limits) push the discharge rate of a battery, but at the expense of heat, degradation & reduced capacity. Example generic discharge curves at increasing C 5th chart down.
https://www.mpoweruk.com/performance.htm

Regular lead acid batteries are usually in environments which have background charging (alternator or generator) to keep them perpetually topped up. Not sure if I'm dating myself but I used to hear 20% sustained drawdown was the typical design tolerance. And if it fell below 50% repeatably, one could expect permanent performance degradation. Sometimes the cost difference can warrant abusing a lead acid or getting a (larger) size where the load represents a smaller percentage of drawdown if weight was no issue.
 
PeterT said:
Happened to be cruising AliExpress & saw this portable tab welding machine.
https://www.aliexpress.com/item/32696319696.html?spm=a2g1y.12024536.productList_2304474.subject_3

There is a place in town that does this. I used them many moons ago. But I guess if you are building your own Tesla.....
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LOL. Cool toy...I like this.

On the original hub related issue, after several failed shipping attempts I finally got my new hubs from the company and they fit. So the old ones got shipped back for free and I am back in business.

Also decided to go with a battery powered mower and got a 40V Brushless on clearance at Lowes. I am busy stripping it down.

The build won't be ready for this season, but I should have it operational in a few months, at least for testing. Can't wait to see my neighbours staring at me through the windows in December as I try to cut the lawn through the snow.
 
PeterT said:
Deep cycle chemistry is more tolerant & forgiving to ...well.. deeper cycling :) Sometimes they are called RV or Marine, but those are ....
Click to expand...

@PeterT , only because we share the same first name and last initial, I thought I'd share this with you... (you too @Johnwa as you sound keen )

You both seem to have a good grasp of battery chemistry and technology. I too am fascinated by this stuff. Here's an educational site I found that has WAY more info than most would want, but is great reading late at night. They are super accommodating to questions as well. I posted a question to them once about the impact of tapping 12VDC from two series-connected batteries in a 24VDC circuit, and they wrote an article a week later. Who responds like that? I can't get my 22 year old kid to text me from his bedroom and it's across the hall :mad:

https://batteryuniversity.com/
 
CalgaryPT said:
@PeterT , only because we share the same first name and last initial, I thought I'd share this with you... (you too @Johnwa as you sound keen )

You both seem to have a good grasp of battery chemistry and technology. I too am fascinated by this stuff. Here's an educational site I found that has WAY more info than most would want, but is great reading late at night. They are super accommodating to questions as well. I posted a question to them once about the impact of tapping 12VDC from two series-connected batteries in a 24VDC circuit, and they wrote an article a week later. Who responds like that? I can't get my 22 year old kid to text me from his bedroom and it's across the hall :mad:

https://batteryuniversity.com/
Click to expand...
That’s the exact website I was told to read up on

Freaky but cool
 
banggood.com had a battery terminal welder for about $100, last time I checked. I almost bought it on spec.
 
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