Anyone own a Hemingway power hacksaw?

[HollowpointParticipant @hollowpoint]

Anyone own a Hemingway power hacksaw that can help me?

I acquired a Hemingway hacksaw a while ago and tried to use it yesterday, I’ve come across a problem with the motor shaft spinning in the flywheel. I took a quick look and it’s a strange arrangement, with the keyed shaft of the motor sitting in a threaded bush which in turn appears to be holding the flywheel on with a nut? No key? It’s a bit odd. I was wondering if anyone has plans or knows how how it should operate?

I am also missing the cap that covers the oil reservoir so any details of that would help too.

 

Thanks in advance.

[MichaelRParticipant @michaelr]

I think it is called a drive collet see this Link https://www.youtube.com/watch?v=SdGNWgqaDXs&list=PLFlTrZ2MXBjjJrbDPWU00OVtlYKaL0tdP&index=9

Final Build showing flywheel fixing https://www.youtube.com/watch?v=t6tFTFQX6IM&list=PLFlTrZ2MXBjjJrbDPWU00OVtlYKaL0tdP&index=14

[HollowpointParticipant @hollowpoint]

Ahh, that helps! 👍

I’ll have to dismantle it further.

[bernard towersParticipant @bernardtowers37738]

Yes I did watch that Michael and think that the collet performance could be improved by much better fitting parts and possibly finer threads on the collet closer with maybe 4 slots and definitely drilled holes at the end of the slots to make it more flexible.

[Clive FosterParticipant @clivefoster55965]

Basically a poor boys taper lock fitting. Spanning a keyway like that isn’t going to help the grip. The collet walls are inevitably thin and will distort. Best to put filer piece in.

Clive

[HollowpointParticipant @hollowpoint]

So I took it apart and it is indeed a tapered collet type arrangement.

I cleaned all the oil off and tightened it up as much as I could, and although it’s better, it still slips. 😔

I was surprised to see just how thick the wall of the collet is! Its probably about 1/8″! So you really have to wrench down hard to get it to squish up. No holes at the end of the slots either, so maybe adding them is an option. I can’t say I’m impressed. What’s wrong with a keyed slot or grub screw? 🤦🏼‍♂️

[Hollowpoint]

On Hollowpoint Said:

… I can’t say I’m impressed. What’s wrong with a keyed slot or grub screw? 🤦🏼‍♂️

Just a guess, but this kind of slippy arrangement is sometimes used to protect a machine in the event of a crash.   Like a shear pin, but less dramatic.

If so, I’m not sure why it should spin prematurely.   As the saw is second-hand, it may have taken a wallop in the past causing the joint to let go and maybe damage was done before the taper released.  I’d carefully inspect the whole saw looking for damage, especially any sign of stiffness in the mechanism as it turns.  Could be something is bent, causing enough extra friction to force a slip.  Or, maybe the build is incorrect, perhaps misaligned parts.   Not everyone is a good machinist, or can read a plan correctly, blush!

Dave

[Hollowpoint]

On Hollowpoint Said:

So I took it apart and it is indeed a tapered collet type arrangement.

I cleaned all the oil off and tightened it up as much as I could, and although it’s better, it still slips. 😔

I was surprised to see just how thick the wall of the collet is! Its probably about 1/8″! So you really have to wrench down hard to get it to squish up. No holes at the end of the slots either, so maybe adding them is an option. I can’t say I’m impressed. What’s wrong with a keyed slot or grub screw? 🤦🏼‍♂️

The Hemingway hacksaw is a Westbury design for amateur constructors.  He used the collet fixture with success on the flywheels of his engines, such as the Wyvern.  Why did he not use a key?  Because he recognised that very few amateur workshops have facilities for keyway broaching or slotting.  And, in my experience, grub screws do not provide a positive fixing where any significant power is involved-ok for a Stuart 10 flywheel but not anything much bigger.

Rod

[HollowpointParticipant @hollowpoint]

Most people own a hand file!

[Roderick JenkinsParticipant @roderickjenkins93242]

I own several but, sadly, not the skill to make a nice, snug, flat bottomed slot 😕

[bernard towersParticipant @bernardtowers37738]

Just a thought I presume it takes std hacksaw blades, would  it be better with a finer blade?

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