Electric Racing Chainsaw Build, Help Please

[stan.distortion]

There are a couple more on hobbyking that are worth a look for a saw:
https://hobbyking.com/en_us/1-5th-brushless-motor-780kv.html?queryID=475e0f217853f100b8239d4284fa5746&objectID=45264&indexName=hbk_live_magento_en_us_products_hbk_price_stock_7_group_0_desc
https://hobbyking.com/en_us/turnigy-aquastar-t20-3t-730kv-1280kv-water-cooled-brushless-motor.html?queryID=76f496e5fcc42206415e4f14fa8b6cc1&objectID=45198&indexName=hbk_live_magento_en_us_products_hbk_price_stock_7_group_0_desc

They're fairly low reving compared to other motors of the same size, "only" around 25k. SSS claim their 56104 is good for 50k rpm and I've not come across anyone using them complaining about exaggerated figures but no matter how good they are around 25-30% of that 14kw is going to be wasted as heat. That still leaves at least 10kw of output power for less than 1.5kg and at a fairly easy speed to gear down for a saw, 10-12k rpm is normal for an unloaded production saw and 20k would be an easy figure for hot saw chain speeds so only around 2 or 3 to 1.

There are some crazy high reving 70mm inrunners around that might be worth a look when they get more popular but for now 56mm is the low hanging fruit, putting in more volts to see what revs they'll hold together to isn't going to break the bank.

Unless the OP or his saw builder already has a good grounding in electric drives,controller set up and programming, and the finesse of high performance lipo packs etc etc... i would suggest the first move would be to get a team together with the necessary skills and experience.
You do not want to have a hi power lipo pack burst into flames either in your shop or on the competition platform !

On a side note, if anyone knows of a readily available electric pump for the chain oil please let me know! It's the only thing that's held up this project moving from a converted IC saw to a custom made electric. The solenoid pumps used on engineering machine oilers are about the ideal but it needs to be much smaller. That would open up the option for load and speed regulated oiling rather than just speed. Thanks

Most domestic Espresso Coffee machines use a small, low flowrate, solenoid pump (ULKA EX 5) available in various voltages.
https://www.ebay.com.au/itm/Breville-Sunbeam-DELONGHI-Coffee-Machine-PUMP-48W-230V-50Hz-ULKA-EP5/153551117816?_trkparms=aid%3D1110001%26algo%3DSPLICE.SIM%26ao%3D2%26asc%3D20160908110712%26meid%3Da545afe11e7e4732b8118f01d68516d6%26pid%3D100677%26rk%3D5%26rkt%3D30%26mehot%3Dag%26sd%3D153643214804%26itm%3D153551117816%26pmt%3D0%26noa%3D1%26pg%3D2386202%26algv%3DDefault&_trksid=p2386202.c100677.m4598
They are used with water, but would handle oil im sure

That look absolutely bang on! Thanks a lot, so long as they're ok with oil they should be perfect for the job I'll probably have a look at making a standalone unit, pump, tank and control all in one. Motorcycle chain oilers are a godsend for anyone doing high milage and I'm sure a lot of folks on e-bikes would say the same if they where readily available.

A bump to the safety concerns with lipo's too! Saws usually live in a shed with sawdust, bits of timber, petrol cans, oil cans.... the thoughts of a lipo on charge in the middle of it are giving me a cold sweat!

 

[Punx0r]

We may have a winner!

https://www.autocar.co.uk/car-news/industry/uk-firm-launch-worlds-most-power-dense-ev-motor

I guess the claimed weight is the rotor and the motor's part of the housing shared with the controller & diff and it'll be a year even before prototypes are made, but it's 220kW for 10kg (22lb). Is that enough??? :lol:

SSS claim their 56104 is good for 50k rpm and I've not come across anyone using them complaining about exaggerated figures but no matter how good they are around 25-30% of that 14kw is going to be wasted as heat. That still leaves at least 10kw of output power for less than 1.5kg and at a fairly easy speed to gear down for a saw, 10-12k rpm is normal for an unloaded production saw and 20k would be an easy figure for hot saw chain speeds so only around 2 or 3 to 1.

This one?

https://www.turbines-rc.com/en/50-56mm-brushless-motors/1878-tfl-sss-56104-650-motor-56mm-650kv.html

 

[speedmd]

The Avid claims 12000 rpms on the AF125 https://avidtp.com/product/evo-motors/ , and claim they can make a faster turning motor. Nice cooling setup and center rotor design. Looks relatively bullet proof at 60kw - 100kw @ 20 seconds. Looks to be solid built and not sure how much weight can be shed if need be.

 

[Frank]

Interesting thread.... I like the idea of rigging up some sort of prototype, even if it's bench mounted (feed the wood to the saw, not the other way around) in order to get some data. A cheaper brushed DC motor and controller could get you a lot of data and might allow better insight into what's really needed.

 

[Ianhill]

Owner pushes 50 watt bursts on this bad boy still there now trying to chop a pencil haha.

 

[Punx0r]

The Avid claims 12000 rpms on the AF125 https://avidtp.com/product/evo-motors/

Shame they don't do an AFR62.5, it'd be perfect!

 

[speedmd]

The Avid claims 12000 rpms on the AF125 https://avidtp.com/product/evo-motors/

Shame they don't do an AFR62.5, it'd be perfect!

Nice carbon ring to keep magnets in place. Could eliminate the outer plates and stator support plates could be greatly cored - finned to easily air cool this design. Interesting trade off, with the inner stator-twin rotor vs the twin stator - inner rotor axial flux setup. Dual rotors may challenge the single cylinder rule.

Magnax showing a smaller 12k rpm motor. https://www.researchgate.net/figure/MAGNAX-motor-series-specifications_fig17_326294480

 

[Hillhater]

Magnax looks good on paper and CGI images....but..

”Magnax develops and manufactures custom motors for eMobility OEM.
We do not sell off-the-shelf products”.

 

[serious_sam]

NeuMotor 4440
- 4.7kg
- 40kW peak
- 10,000rpm max (might be able to overspeed a little bit?)

Sounds like they do custom stuff too.

https://neumotors.com/neumotors-4400-series-bldc-motors-1000-to-4000-watt-class/#4440

 

[speedmd]

Magnax looks good on paper and CGI images....but..

”Magnax develops and manufactures custom motors for eMobility OEM.
We do not sell off-the-shelf products”.

I could understand that given the cost of the AF designs. Twin rotor designs could be argued (If they cared to look deep into this) as a "two cylinder" type electric motor. Looking like this is going to need to be a custom motor or gear box if over 12000 rpms is needed. The required battery voltage, 400 or 750 vdc may need some extra precautions.

Other than rotors coming apart at higher revs on some, the topology looks like it could easily spin the required speeds. Incredible power density on them. The possibility of hand holding a 200+ HP Hot saw is insane.

 

[Punx0r]

Looks like a good candidate. Any idea on pricing and availability?

 

[speedmd]

Looks like a good candidate. Any idea on pricing and availability?

You buying? :lol: Let me know and I will ask. :wink:

 

[speedmd]

Emrax is telling me the existing 208 design can not be run past 7000 rpm. Looking like a gearbox would be required with them.

 

[Punx0r]

Boo. Although I wonder if doing so would exceed some design safety margin or whether they know from experience it will instantly grenade...

 

[speedmd]

It is rated at 6000 rpm so 7000 is already pushing it quite a bit. Even with doubling rpm by gearing, it still should have more torque than the gasser. Would be nice to have some data on the rpms the saw is using now. Even a simple tac should be visible while cutting a few tests. https://www.ebay.com/itm/Universal-Motorcycle-Tachometer-Speedometer-Gauge-gauge-0-16000RPM-E6A9/333537053414?epid=9012437414&hash=item4da85b8ae6:g:eBEAAOSw6O9eYhdr

 

[Ianhill]

Cut a foot wide stump of some soft wood with my 36v erbauer chainsaw and had sparks coming off the chain thing went blunt in seconds, nothing wrong with the oiler so mental chain speeds will need loads of oil and a new chain every go.

 

[speedmd]

Chain speed has little - nothing to do with you hitting dirt- grit which will most times spark and dull a chain as you experienced. Trees often pull debris well into the stump. Always use a old chain for stumps. My saw found a clothes line (4" pulley and hook) a full foot inside of a 5 foot diameter log last year. Lost most of a few chain teeth there.

 

[Ianhill]

Chopped up logs for a good half hour on a 36v 5ah battery and used about 45wh not to bad really considering the stump ruined the chain it's for the bin on the plus side the electric got some good torque sorted out this stubborn bigger that was weaved into a bigger tree that was staying so made things more difficult had to cut in sections rather than one big timber.

The bar is only 16inches mind so to get through a foot ain't to bad at all quite impressed with the run time to work done good effort very useful as a inbetween bit of kit.

 

[Hillhater]

It is rated at 6000 rpm so 7000 is already pushing it quite a bit. Even with doubling rpm by gearing, it still should have more torque than the gasser. Would be nice to have some data on the rpms the saw is using now.

Why do you doubt the information from the OP ?
The OP has previously told us 9-11,000rpm....i assume from data supplied by his motor man.
Since this is a competition saw, with a pro built, highly tuned motor,.. im sure the motor builder would know exactly what rpm range that saw is performing at.
A serious Esaw builder would get one or more of the chosen motors (208/188/??, etc) and strap them onto a dyno to see what their limits actually are under the application requirements...IE 10 sec @ max rpm, max power etc
Ditto controller selection.

Cut a foot wide stump of some soft wood with my 36v erbauer chainsaw and had sparks coming off the chain thing went blunt in seconds, nothing wrong with the oiler so mental chain speeds will need loads of oil and a new chain every go.

OR...you could invest in a tungsten tipped chain,.....
.....and if you plan to hog into reinforced concrete, they do make full diamond coated chains for cutting holes in walls !

 

[speedmd]

The OP has previously told us 9-11,000rpm...

Not finding that in original spec. Several different size motors discussed. 250 cc looks to be very different so It would be nice to have a smaller target chain speed to shoot at.

4 stroke

 

[Hillhater]

.......
I've reached out to the most knowledgeable people in the current 2 stroke hot saw game and while they can't give me real dyno numbers, they can give me their best estimates. Here are the numbers that get tossed around a lot.

9000-11000 max rpm
290 feet per second chain speed
50-60 hp
torque ???

PS, those Dyno curves you posted....are all for 4 stroke motors !
The saw motors are 2 stroke..bored, and tuned, so no “stock” dyno data is likely to be representative :wink:

 

[speedmd]

You got me hill! :lol: found -Added a modern 2 cycle.

Still, I would think it be nice to know what the real chain speed is running. No way to get to 290 ft/ sec spinning a 17 tooth 404 chain at 10000 rpms. You would need some 13000 rpms spinning a 20 tooth sprocket. The AF claimed torque could allow it to just spin a larger sprocket if the working rpms are close enough.

 

[Hillhater]

The 290fps was a calculation the Op did based on measureing the chain OD when wrapped round the drive sprocket.
That calc has a huge error due to the difference in OD and drive pitch diameter.

....
When I lay the 404 high tooth chain tight against the smaller 16 tooth sprocket I end up with a 5 inch radius.
A 5" radius at 11000 rpm gives me a chain speed of 239 feet per second. I'm unsure what the radius on the 17 and 18 tooth sprockets are as I don't have one on hand at the moment. A 6" radius at 11000 rpm gives a chain speed of 287 fps, which gets close to that 290 fps number that has been tossed around.

So better to stick with drive sprocket rpm as the target than any estimated chain speed.
BUT.. it shure would be nice to have the possibility to experiment with higher chain speeds...which the use of a Jack shaft drive would give you ! :wink:

 

[speedmd]

better to stick with drive sprocket rpm as the target than any estimated chain speed.
BUT.. it shure would be nice to have the possibility to experiment with higher chain speeds...which the use of a Jack shaft drive would give you ! :wink:

No doubt, ability of swapping out a sprocket or gear set to dial in rpms is attractive. Chain speed is key IMO to better zero in on what are most workable chip load ranges and determine which way to dial power depending on how the chain is working in the logs. Many ways to skin a cat.

 

[speedmd]

The emrax 208 size motors peak torque, could pull or push the saw with over 250 pounds force using a 2:1 gear increase while driving a 18 tooth sprocket. Is that something manageable if the chain were to lock up in the log?