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View Full Version : Flexible power shaft manuf. and power handling capacity? (project Binky...)



MattiJ
11-04-2018, 08:34 AM
Was watching latest episode of Project Binky and they intended to run car alternator AND ac compressor trough flexible power shaft.
Like shown in this part of video:
https://youtu.be/WIyxrvO3dRk?t=1701

To me the power shaft looks like wayyyyy undersized for the task. Anyone recognize the model/manufacturer? I'm curious to know what kind of specifications for RPM and torque the manufacturer gives.

outlawspeeder
11-04-2018, 08:41 AM
I've seen a longer and thinner one driving Main gear between two gearboxes. I am not say it could handle it, just that I've seen smaller.

softtail
11-04-2018, 09:08 AM
I saw that as well.. kinda begs the question 'why', but then so does the whole project.

A.K. Boomer
11-04-2018, 09:09 AM
Even if not undersized and it could handle it to me it's not the way to go - flexing steel at high rpm's takes energy and creates friction - also the casing is holding the innards from going haywire so there's internal friction on the sheaths,

used to be an ok practice for things like speedo cables but even they gave it up after so many miles and im glad things are electronic now...

softtail
11-04-2018, 10:33 AM
Even if not undersized and it could handle it to me it's not the way to go - flexing steel at high rpm's takes energy and creates friction - also the casing is holding the innards from going haywire so there's internal friction on the sheaths,

used to be an ok practice for things like speedo cables but even they gave it up after so many miles and im glad things are electronic now...

And getting cooked by engine heat....

Magicniner
11-04-2018, 01:44 PM
Did we hear that it's an Aircraft related part?

I think they've done their research properly and have an appropriate part.

One possibility -

https://www.elliottmfg.com/products/flexible-shaft/

I think it'll be fine ;-)

MattiJ
11-04-2018, 02:26 PM
Did we hear that it's an Aircraft related part?

I think they've done their research properly and have an appropriate part.

One possibility -

https://www.elliottmfg.com/products/flexible-shaft/

I think it'll be fine ;-)

https://www.elliottmfg.com/products/flexible-shaft/flexible-shaft-products-core-shaft-chart/

OK... 0.5" core is rated for max 2300rpm and about 100 lb-in. Thats maximum power of 3.5hp.
Would suffice for alternator if you match the rpm range enough well. Add another 3-6 hp for the AC ..
Well maybe they used something considerably better than mentioned elliot mfg.
Curious to know if it breaks on first start but I'm affaid I'm too senile after 50 years when they finally finish the car to check for the progress ;)

A.K. Boomer
11-04-2018, 02:34 PM
Would be curious to find the HP consumption specs for the drive unit itself - that tells allot right there, of course variable with whatever angle it's forced to work at and ramping up it's consumption with more angle... I would look at it as a last resort and patch work afterthought at best... great for weedeaters though and yes greatly depends on applications themselves.

MattiJ
11-04-2018, 02:44 PM
Would be curious to find the HP consumption specs for the drive unit itself - that tells allot right there, of course variable with whatever angle it's forced to work at and ramping up it's consumption with more angle... I would look at it as a last resort and patch work afterthought at best... great for weedeaters though and yes greatly depends on applications themselves.

Can't be much for that size of part. Anything more than 0.1...0.2hp and it would eventually melt.

Magicniner
11-04-2018, 03:14 PM
Curious to know if it breaks on first start

Max alternator load, zero AirCon load, hmm, what's the chances?

The guys at Bad Obsession seem to do adequate research and deliver actual results!

softtail
11-04-2018, 03:47 PM
This was my guess:
http://www.sswhite.co.uk/standard-flexible-shaft-assemblies/

Many of the applications seem be for intermittent use.

Anyways, seem they have no option but to use it.

Mark Rand
11-04-2018, 03:58 PM
Anyways, seem they have no option but to use it.

What's wrong with a Cardan shaft?

J Tiers
11-04-2018, 04:02 PM
Looks like they CHOSE to do that, but could have done a solid shaft version that simply would work with no questions.

That flex shaft may work. I have low power ones that spin at maybe 12k rpm with more extreme bending. (Foredom tool). So just the rpm is not a killer.

Power and rpm might be, acceleration might be, lube might be. The bends are not too bad, I would be more concerned about acceleration and load changes on what is driven by rhe flex shaft.

MattiJ
11-04-2018, 04:06 PM
This was my guess:
http://www.sswhite.co.uk/standard-flexible-shaft-assemblies/

Many of the applications seem be for intermittent use.

Anyways, seem they have no option but to use it.

That looks like perfect candidate.

To me it looked like they could have run intermediate shaft to somewhere on top of gearbox and belt drive from there to alternator&compressor but its hard to say from video.

Interesting solution, we went trough about every other option and some others with the unholy marriage of cramming Saab engine to Lotus Elise .. :D
Binky is even more hardcore project than that and I feel like there is not a single unmodified stock part left on Elise either. (Chassis and suspension is close to stock but for example transaxle is built out of 4 different sources to make everything else fit in the wanted way)

softtail
11-04-2018, 04:19 PM
They should have done an alternator scoop/bulge on hood ;)

Peter.
11-04-2018, 04:35 PM
I always enjoy the episodes though sometimes there's quite a wait. They seem to have confused the driven end and driving end of that shaft though :)

MattiJ
11-04-2018, 04:43 PM
I always enjoy the episodes though sometimes there's quite a wait.
I have watched some of the episodes more than twice just to see/remember all the neat fabricating tricks.
The wiring loom episodes gave me traumatic flashbacks :eek:

Doc Nickel
11-04-2018, 05:45 PM
It's probably worth keeping in mind that "Binky" is not going to be a daily driver. It's like any other custom/classic that a collector owns- you drive it a couple times a year for fun, take it to a few shows, maybe take the occasional trip in it, but it's not the car that you get into every morning for your forty-mile drive to work each day.

As such, the car will likely be lucky to see 20K miles in ten years after it's finished. It really is a "just 'cause I can" type of fun project.

Yeah, it might not be the kind of thing a proper auto manufacturer would build, and expect for it to last 200,000 miles, but in this case, trying to shoehorn that engine and drivetrain into that tiny a car, well, corners have to be cut here and there.

Personally, the series is easily my favorite on YouTube, even surpassing This Old Tony. The combination of the project itself being so fun and interesting, their sense of humor, and their clear skill at problem-solving, designing and fabricating makes for a top-class work. It's the kind of show I used to hope that programs like Overhaulin', Monster Garage and American Hot Rod would be. And I hope that it's popularity drives some big studio- like Netflix or Amazon- to commission a similar show. A detailed build, and fun, humorous hosts, rather than the scripted idiot-fest drama those other shows had.

Doc.

wierdscience
11-04-2018, 10:25 PM
Gasoline weed eater shafts do it all the time,plus IIRC they said "aircraft" which means the HP rating is most likely conservative.

danlb
11-04-2018, 11:43 PM
Chassis and suspension is close to stock but for example transaxle is built out of 4 different sources to make everything else fit in the wanted way



I only watched a few episodes, and enjoyed them. But I have to say, the chassis is about as stock as the one on the Nascar Toyota Camry. I watched them replace the fender wells. And the firewall. And the floor. And the boot. And reskin the doors. And build a new dashboard. And the front of the car body was made to swing up as one piece. And then they rebuilt much of what was rear of the firewall.

I've got to say, those guys are quite inventive. When they are done it will look like a stock Mini, but not up close..

Dan