Kiwi Mk II

[Richard P]

Reeves 2000 sell spring steel by the foot. Not much of a selection, but you'll need some for the float bowl cover clip, regardless of making points. It's inexpensive... But getting the bends in the right place for the carb clip is tricky. I made up a simple bending fixture for mine. I punched some holes in it while I was there, for flexibility as well as aesthetics.

Thanks for that pointer, are you able to share a photo of your perforated cover clip?

 

[Richard P]

As far as points go, Kirk at Hemingway has a stock of the ones ETW specified, but you might not like the price... He also has a stock of tungsten discs if you want to do a home brew. He doesn't advertise these on the website.

If you want to go down the ready-made route, you'll find that Ford model A points are still readily available, and inexpensive.

The Kiwi II is a fun project, and well proven. It does have a bit of a reputation for running hot, though, so you often see pictures of them with an additional fan, to help with this.

When it comes to the cams, you can do them the ETW way, or make harmonic cams. M.E.N has a program to help you do this (camcalc) but because of a coding glitch, you can only use it via internet explorer - not firefox...

Thanks for this. This will be my first go at cutting cams and is a bit further down the line. Excuse my lack of knowledge, but what is the difference between cams cut the ETW way vs harmonic in terms of ease of execution and benefits? Thanks

 

[Richard P]

That's a lot of progress. You'll be finished in no time.

Vince

Thanks Vince. Your thread has been extremely helpful!

 

[methuselah1]

Cams for engines come in two flavours, tangential and harmonic. Tangential cams have straight sides, and a radius on the lobe- the ramp is vicious! I think the first incarnation of the Kiwi used them; they were common in motorbikes of the period.
Harmonic cams have curved flanks, and the ramp to the lobe is far more gentle. They made the tangential cam near obsolete.
ETW's method produces a good approximation of a harmonic profile; then he approached D.H.Chaddock for further help refining the design, which the Professor did using his lathe and an improvised spindle and flycutter on his cross slide. The plan is to take a cut, then roll the lathe mandrel a couple of degrees, set the cross slide for the next cut, rinse and repeat. Although I have the same lathe, I do mine in a vertical mill with a rotary table. I put a 1/16" keyway in the cam blank, and a corresponding key on the mounting peg. Using a big tee slot cutter, I can mill both profiles in one setting, or if I only have an endmill, I can flip the blank upside down, because of the keyway.
This produces a near perfect harmonic profile, with a series of tiny facets, which are carefully removed with a dead smooth file before hardening.
That's where camcalc comes in. It generates all the figures for you. Keep them tucked away, as ETW used the same cam profiles for several of his other engines too!

Now, I'll try to get some photos of the carb clip to you later, (batteries are charging as I type) but my camera has been poorly, so I'm not going to make any promises!

 

[methuselah1]

"Tungsten point discs can be made quite readily by slicing TIG electrodes with a Dremel abrasive disc. "

good to know that, thanks for the tip...
i have failed to cut disks in 3 mm tungsten carbide tool bits !
silver contacts work well with small engine but don't last long.

Tungsten (W) actually machines quite readily. Tungsten carbide (WC) is a different animal. It's a tungsten-carbon alloy. It's produced in powder form, and tool manufacturers add a binding agent and sinter the stuff into the cutters we use. The main problem with tungsten is the cost of the damn stuff, which is why purchased blanks from people like Hemingway can be handy, and car points become favourable!

Andrew UK

 

[Richard P]

Cams for engines come in two flavours, tangential and harmonic. Tangential cams have straight sides, and a radius on the lobe- the ramp is vicious! I think the first incarnation of the Kiwi used them; they were common in motorbikes of the period.
Harmonic cams have curved flanks, and the ramp to the lobe is far more gentle. They made the tangential cam near obsolete.
ETW's method produces a good approximation of a harmonic profile; then he approached D.H.Chaddock for further help refining the design, which the Professor did using his lathe and an improvised spindle and flycutter on his cross slide. The plan is to take a cut, then roll the lathe mandrel a couple of degrees, set the cross slide for the next cut, rinse and repeat. Although I have the same lathe, I do mine in a vertical mill with a rotary table. I put a 1/16" keyway in the cam blank, and a corresponding key on the mounting peg. Using a big tee slot cutter, I can mill both profiles in one setting, or if I only have an endmill, I can flip the blank upside down, because of the keyway.
This produces a near perfect harmonic profile, with a series of tiny facets, which are carefully removed with a dead smooth file before hardening.
That's where camcalc comes in. It generates all the figures for you. Keep them tucked away, as ETW used the same cam profiles for several of his other engines too!

Now, I'll try to get some photos of the carb clip to you later, (batteries are charging as I type) but my camera has been poorly, so I'm not going to make any promises!

Thanks for the comprehensive reply, really helpful! Harmonic cams are clearly the way to go and will use the vertical mill and rotary table option when II get to that stage.

 

[methuselah1]

Thanks for the comprehensive reply, really helpful! Harmonic cams are clearly the way to go and will use the vertical mill and rotary table option when II get to that stage.

I omitted to mention (as if you hadn't realised) that I key my cams to their shafts on all my engines.

Unfortunately my camera is defunct, so no photos, yet. My Mum wants to visit me next week, and she's got one of those fancy telephones that can take good photos - I'll ask her to help.

I did say that ETW used the same cam profiles in several engines, but when building an A/C Seagull, or one of the others, I had to reduce the cam base circle due to a clearance problem. All hail camcalc! It made that very easy to do. Have you been able to find it?

-Andrew UK

 

[H. K. Barrows]

Hello I make points quite often I use 1/8 Tig electrodes I just slice off 1/16 discs. But more than often I use point sets that where used in a car that was popular in 1950 it"s name was Crosley little Like the Mini. for us colonist Whiteny auto part have them. sets come in two pieces an adjustable threaded point ground. For the points I make, I use .010 tho. feller gages. I engines that I have used for many years. HKB

 

[Richard P]

I omitted to mention (as if you hadn't realised) that I key my cams to their shafts on all my engines.

Unfortunately my camera is defunct, so no photos, yet. My Mum wants to visit me next week, and she's got one of those fancy telephones that can take good photos - I'll ask her to help.

I did say that ETW used the same cam profiles in several engines, but when building an A/C Seagull, or one of the others, I had to reduce the cam base circle due to a clearance problem. All hail camcalc! It made that very easy to do. Have you been able to find it?

-Andrew UK

Thanks Andrew!

 

[Richard P]

Hello I make points quite often I use 1/8 Tig electrodes I just slice off 1/16 discs. But more than often I use point sets that where used in a car that was popular in 1950 it"s name was Crosley little Like the Mini. for us colonist Whiteny auto part have them. sets come in two pieces an adjustable threaded point ground. For the points I make, I use .010 tho. feller gages. I engines that I have used for many years. HKB

Thanks for that. I have ordered a set of points so will see how big they are vs what you mention. Hopefully they will do.

 

[methuselah1]

I never thought of using feeler stock! You used to be able to buy it by the roll... How easy is it to shape? The Kiwi ended up getting dyno tested by Prof. Chaddock, and he managed to wring 0.64hp out of his example- at 8000rpm! Do you experience any point bounce?

Although I expect ANY automotive points could be adapted in most cases, (engines like ETW's Seagull must have a custom built breaker 'cos of the design) I mentioned the Ford "A" points because they are one bit, and no larger than the specced item.

Another thing I'd forgotten, is that I've read of people pilfering the tungsten contacts from morse (code) keys. These are handily mounted on threaded tails. There must have been one hell of a glut after the war, as everyone seems to have at least one- even me!

 

[Richard P]

Here is some more progress on the Kiwi. I've been working on the rockers and other elements of the rocker assembly. Some sanding and polishing still to do, but overall these components have come out ok.

 

[methuselah1]

Photos of the float bowl clip, courtesy of mater. Unfortunately, she couldn't quite grasp what I wanted, so whilst they're not as good as I hoped, you should be able to get the idea.

Send me an address to [email protected] and I'll forward them. I can never work out how to upload photos, so if you could do that on my behalf, that'd be great.

-Andrew UK

 

[Richard P]

Thanks Andrew! As requested I've uploaded the photos that show the spring steel clip you made for your Kiwi.

Many thanks

Richard

 

[Richard P]

Spent some challenging hours this week working n my first ever camshaft for the Kiwi. First struggled to get the Camcalc software to work but was ably assisted by other forum members - thanks! And then suffered a serious run out problem which I tracked back (eventually) to the baseplate supplied with a cheap import rotary table chuck being way out of square. I resorted to mounting a collet block holder on the rotary table and got a pretty decent result in the

end.

 

[methuselah1]

Well done!!! Very satisfying, isn't it!

Did you get it right in one go?

Andrew UK

 

[Richard P]

Well done!!! Very satisfying, isn't it!

Did you get it right in one go?

Andrew UK

Yes, very satisfying. As I mentioned, there was a huge runout error in the baseplate of the chuck I first used, but luckily it resulted in undercutting one side of the cam. So when I swapped to the collet fixture instead I was able to save the part by recutting it and removing the excess material. So two goes so to speak, but just the one part!

 

[Richard P]

Been working on the crankshaft this week, but have now pretty much got there. Just the oil passagway holes to seal. First time making a crankshaft from solid so fairly nerve wracking as more more and more invested hours are at risk of a c*ck up! Pleased with final result which spins nicely in the bolted together crankcase.

 

[Richard P]

The bronze balance weights and custom bolts complete the crankshaft assembly...

 

[Richard P]

I've been working on the piston for my Kiwi Mk 2. It is the first time I have machined a piston for an IC engine and had to hit the finer tolerances required. Took it slowly and it seems to have come out ok. Piston rings seat nicely after a little bit of additional fettling.