Pump Drill Technique

[Stringmaker]

I made a fairly rough and ready one of these last night (first attempt), having done a lot of reading on them.

It's a bit of a bodge, using bamboo, hand sawn offcuts and masking tape, along with a leather shoelace. That said, it does look like a pump drill!

My question is around the size and weight of the flywheel in relation to the efficiency in generating an ember. At the moment I'm using a sawn piece of a thick branch, but soapstone is mentioned a lot which is obviously heavier.

All other things being equal, is a heavy flywheel better than just an adequate one? My guess is that it will be as it must add to the downward pressure when you drill, therefore being more effective?

I need to properly fix my wood bit to the drill and I'm good to go.

My final aim is to build a "king size" version maybe using a wooden broom as the drill/hearth, such that a team of two or three kids can use it together.

All comments and advice welcome

 

[sasquatch]

No advice for the flywheel but I'll be watching this with interest, I've always wanted to have a go at one of these. Keep us posted on your progress please!

 

[Stringmaker]

No advice for the flywheel but I'll be watching this with interest, I've always wanted to have a go at one of these. Keep us posted on your progress please!

I certainly will.

The pressure is on now!

 

[sasquatch]

It certainly is! Best of luck with it...

 

[FerlasDave]

You dont really need a whole lot of weight with a pump drill, just enough to hold the drill firm. Because you can get a lot more revolutions which will mean more friction build up anyway. As for the spindle you want something inbetween bowdrill and hand drill size.

 

[Stringmaker]

You dont really need a whole lot of weight with a pump drill, just enough to hold the drill firm. Because you can get a lot more revolutions which will mean more friction build up anyway. As for the spindle you want something inbetween bowdrill and hand drill size.

Thanks for that.

I must say that most of the kit I've seen has wooden flywheels, which is obviously easier to find and make. I'll post a photo sometime of my crude setup as I made it yesterday. Hopefully it should progress to something which both looks the part and works...

 

[Toddy]

The ones I've used just had a stone whorl at the bottom. You can make one out of clay though, let it air dry hard and soft fire it in the oven or hearth. It's still a bit fragile. I know someone who covered his whorl in leather

Somewhere I have one that was made from a wooden disk but a channel was cut around it and lead poured in.
It's just easier sometimes to keep the momentum going. It only really needs to be heavy enough to keep the spindle down and in the board. The little ones get used to put holes through things like shells. Jewellers used to use them until the little Archimedes screw drills came into use.

It's the balance, spindle shaft length and thickness to baton width, that's just as important to the smooth working of the drill, as is the whorl weight.

Best of luck with it Be interested to see how you get on with it

cheers,
Toddy

 

[FerlasDave]

Thanks for that.

I must say that most of the kit I've seen has wooden flywheels, which is obviously easier to find and make. I'll post a photo sometime of my crude setup as I made it yesterday. Hopefully it should progress to something which both looks the part and works...

Yeah, a wooden flywheel is easy to do, just cut a tree trunk lol.

The key is really in the wood you use, just like any other friction fire. Im sure you'll figure it out though.

 

[Stringmaker]

Thanks all, useful stuff.

I like the idea of a clay whorl; I'm also considering going back to the stone age and just using stones, stems and cordage.

I'll keep a running commentary going on my learning and progress.

 

[Stringmaker]

Current status: I need to produce a new spindle as the bamboo one I had split on me!

I cut it down but then all the proportions were wrong and the drill wasn't up to the job. I do have a photo of it though before it broke so I'll upload that at some point. Mechanically it seemed to work quite well but the longer spindle will be key in generating the power and speed I need at the bit.

I can see why lighters caught on!

 

[Stringmaker]

Latest update:

I cut a new piece of bamboo (until I can get a decent straight piece of wood), fitted a sycamore bit and cut a sycamore hearth board. The setup still isn't right as I think the flywheel is too low on the shaft and out of balance, meaning that the bit pops out of the hearth when you start to drill. I'm also not convinced that the cord I'm using (length of old washing line) is right either; it is too inflexible to wrap and unwrap the drill smoothly and quickly enough.

Onwards to the next problem!

 

[Stringmaker]

Right, I WILL make this contraption work!

After a lot of faffing, the main learning since last time is that a heavy flywheel close to the drill tip makes all the difference. If the flywheel is too high on the shaft and too light then you get no mechanical work and no stability.

Since my bodged prototype using stuff in the garage I've gone for a bit of a "Stone Age" retro look, using round poles and lashings.

I should be in a position to do a proper test run tonight....

 

[Stringmaker]

This pump drill malarkey is not as easy as the pros make it look!

Hopefully I won't make a hash of posting the pics so here goes with the MK1 version:

http://imageshack.us/photo/my-images/37/pumpdrills001.jpg/

This was the bodge using garage scraps, bamboo and washing line.

The "Stone Age" MK2 is this one:

http://imageshack.us/photo/my-images/97/pumpdrills002.jpg/

I had high hopes for this one as I was now using flexible paracord, a lower flywheel and a tapered drill to fit the hearth. However..........I just could not maintain the momentum. The energy just kind of fizzled out and I couldn't get up a good speed.

I'm stumped.

Any suggestions?

 

[Stringmaker]

D'oh!

I posted the links, not the images!

They are still visible anyway.

 

[Toddy]

It's the same as using a bow drill, just get it all nice and warm and slowly burring off hot fibres, then, go for it

I may well be very wrong, but your flywheel looks a bit light.....mind it not only turns but the weight helps keep it all in place and running smoothly in the socket.
Neat way of creating the 'bar' though The one I used had a hole where there had been a convenient knot

I was looking for Patrick's thread, and though I've found it, the photos are down now.
http://www.bushcraftuk.com/forum/showthread.php?t=10652&highlight=pump
Might still be of interest.

cheers,
Toddy

 

[Stringmaker]

It's the same as using a bow drill, just get it all nice and warm and slowly burring off hot fibres, then, go for it

I may well be very wrong, but your flywheel looks a bit light.....mind it not only turns but the weight helps keep it all in place and running smoothly in the socket.
Neat way of creating the 'bar' though The one I used had a hole where there had been a convenient knot

I was looking for Patrick's thread, and though I've found it, the photos are down now.
http://www.bushcraftuk.com/forum/showthread.php?t=10652&highlight=pump
Might still be of interest.

cheers,
Toddy

Thanks Toddy,

I didn't even get as far as maintaining a constant drilling motion; it was more or less one or two pumps and then it stopped. The only way I was getting that baby warm was a blowtorch!

I have been pondering the flywheel a lot; I have the option to double the weight as I split two pieces of birch and they can be glued around the drill. I'm also not quite sure that the crossbar is long enough to give the right angle for the cord to work efficiently. I'll take a look at the thread you referenced; thanks again.

IF I get this working then it will have been a great learning experience which will give me the neccessary credibility when I get kids to use one!

 

[Toddy]

It's a fun tool when it's all working smoothly Surprisingly effective too

Try taping some coins onto the flywheel you have and see if makes any decent difference ? If it does, then that's one thing you can fix to make it easier.

atb,
Toddy

 

[Stringmaker]

I have just this minute finished reading this:

http://books.google.co.uk/books?id=...=onepage&q=pump drill flywheel weight&f=false

Luckily I have just bought "Earth Skills" so I can read it again at home.

As I suspected, and again just like the bow drill, it is a matter of tuning the tool to make sure it is working to its optimum efficiency, and there are specific effects from each component if they are wrong.

Should anybody else out there be rash enough to have a go at this, the key factors seem to be these:

- One complete drill cycle (down then up) needs to be around 4 revolutions. The way to tune this in is to adjust the cord length to give 2 turns on the down stroke.
- The optimum flywheel weight seems to be 1-1.5 kilos or 2.5-3 lbs.
- The crosspiece should be 23-24 inches.
- The tip needs to be 1/2-3/4" diameter

Back to the garage............

 

[Toddy]

My husband tried to make one to those dimensions, it's huge and unwieldy, and that heavy flywheel needs a lot of fixing.
The one I used had a cross bar about two handspans (16" or 40cms) wide, and the flywheel was a flat stone maybe 3cms thick and 12cms/ 5" diameter.
It's the balance that's crucial, not the size.

Good book though

cheers,
M

 

[Stringmaker]

I'll check what dimensionions/weights I'm working with and take it from there.

The specific point about the torque exerted being related to the revolutions (and therefore cord length) was what made me take note. The way I view it is like building an engine; every component needs to be working to its best efficiency or no matter what you do it won't start.

I also like the idea of making a big tool that a team of kids can use.

On another fire-related topic my pressing project is to insert a stone into my bow drill bearing block; if all else fails then I'll cheat and make it using car two-pack bodyfiller!