1920 Harley Model F

[T. Cotten]

This pic, Folks,...

Shows much better how the idle notch is not easy.

(Please note that the friction disc must be perfect first.)

....Cotten

[T. Cotten]

..What i remember Bob saying is something to the effect the disc need to be adjusted to position between the two holes....

He was correct of course, Steve!

But that is entirely determined by the angle upon the disc.
(Attachment shows it as best I can...)
It cannot be adjusted; The disc is either in its 'sweet spot' to close fully, or it isn't.
A higher angle places the disc forward toward the big hole, and a lower would place it toward the rear.

(This brings up a question about L&L's different angles for different 1½" models. If we assume the throttle shafts were in the same place, does that mean the idle bleeds were shifted fore or aft? Everybody swore how simple Linkerts were... Yeah, right.)

Bringing this back to HX models, the angle determines the shape of the idle notch on the disc.
Note how the top of the notch is not quite square to the axis of the shaft. The lower the degree of the angle, the closer it comes to square.
The top of the notch also has an angled face, that should close upon the barrel of the idle screw. A square cut would never close completely, but probably run anyway.

....Cotten

[TechNoir]

Sorry, John, not wanting to hijack your build.

No need to apologise, I am learning too so please carry on.

John

[T. Cotten]

That only confirms my suspicions, Steve,..

That the absolute simplicity of the HX models made them the foundation of all that came later.
(Was there an alternative? ? .. .. . What other inspirations may we have lost?)

Unfortunately, it takes a at least an amateur watchmaker to approximate them now.

I was never that, but I do have some watchmakers' tools!

....Cotten

[Steve Swan]

We are getting off-topic, Steve!

(Although they lacked the L&L slot, Schebler's DLXs originated the dual circuits design, 'idle' and 'power', so we have left the HX zodiac, but still in the galaxy?)

Did Mr. Paulette give any insights as to how the idle circuit suddenly reverses itself?
We know the Armored School Handbook explains it as when the vacuum at the nozzle becomes sufficient, but...

Does it always flush itself like a toilet, or if held at that critical RPM, might it gurgle and reflux?
Any observations are noteworthy, thanks!

....Cotten
PS: Yeah, the "flat spot".

PPS: Were there any earlier designs with "circuits", Anybody?
(Not that it could knock George off his pedestal; I've just never held a Hedstrom or any of the really early ones in my hand.)

Alas, the answer is no, Tom! What i remember Bob saying is something to the effect the disc need to be adjusted to position between the two holes. I'll look through my notes from those times and see if i can find anything else that might illuminate. Sorry, John, not wanting to hijack your build.

[T. Cotten]

We are getting off-topic, Steve!

(Although they lacked the L&L slot, Schebler's DLXs originated the dual circuits design, 'idle' and 'power', so we have left the HX zodiac, but still in the galaxy?)

Did Mr. Paulette give any insights as to how the idle circuit suddenly reverses itself?
We know the Armored School Handbook explains it as when the vacuum at the nozzle becomes sufficient, but...

Does it always flush itself like a toilet, or if held at that critical RPM, might it gurgle and reflux?
Any observations are noteworthy, thanks!

....Cotten
PS: Yeah, the "flat spot".

PPS: Were there any earlier designs with "circuits", Anybody?
(Not that it could knock George off his pedestal; I've just never held a Hedstrom or any of the really early ones in my hand.)

[Steve Swan]

i very much enjoy following the discussions in your thread, John. Particularly Cotten and Eric's comments, not to mention yours, you guys are into some advanced stuff that i can glean some information from at least as much as i understand what you are talking about. When Cotten was talking about the idle slot, it brought me back to when i was under Bob Paulette's tutelage, this would have been in the mid-1980's, i drew out the idle circuitry, you can see that idle slot, thought you might enjoy perhaps.

idle slot.jpg

[T. Cotten]

Tom is right, the notch is a tedious job. I see things like this in ancient objects and I stand in awe of the engineers, and fixture makers of that day who figured out how to do these things efficiently, productively, and somehow made money doing it.

Its the lost lore of the Ancients, Eric!

Even with my forensic study, I would be a bigger fool to guess how they did it. But here goes...

They made lots and lots of batches. Then they could pick through them for the best fitting hardware, but it still took genius (George Schebler himself), resourcefulness, and worker dedication nearly extinct today.

(Even Linkert's idle slot is still as enigmatic to me as the Egyptian pyramids.)

....Cotten

[exeric]

Tom is right, the notch is a tedious job. I see things like this in ancient objects and I stand in awe of the engineers, and fixture makers of that day who figured out how to do these things efficiently, productively, and somehow made money doing it.

[T. Cotten]

.. Unless you have a better method?...

Not much better, John!

I fixture the disc firmly in the shaft, indexed within the carb body at 'zero daylight', and then rough out the notch through the idle screw hole itself.

Then it still has to be tediously filed/stoned perfect, re-installed for inked inspection a couple of dozen times at least.
(As it was for the friction disc...)

I never could charge enough, but I had no other way to get it right.

....Cotten

[TechNoir]

There are times I wish 'metric' was more available here, John!

We are reasonably fortunate here that whilst we are officially metric, most inch sizes are also readily available, not as easily as metric but certainly not uncommon.

So,... How do you plan to cut the notch to fall perfectly upon the idle screw?

....Cotten

I was thinking I should get the disc right first and then, with it in place carefully mark the notch position and cut it out small piece at a time.

Unless you have a better method?

John

[T. Cotten]

There are times I wish 'metric' was more available here, John!

(Recently I finished a Yale Scheb that had a 14mm bore.)

So,... How do you plan to cut the notch to fall perfectly upon the idle screw?

....Cotten

[TechNoir]

You will want brass sheet to match, John!

I have some. I have 1.0mm and 1.5mm so I ordered 1.0mm and 1.5mm saws.

Ten degrees aims best over the idle screw. Twelve could very well work, with patience to fit the notch with a jewelers' file and ink.
(Just like fitting a friction disc.)

I could easily adjust for 10 degrees.

Why would you bore the pin hole? That's the very very last operation, after assembly, and even Schebler aimed different every time.
(I used the original hole through the cam for a guide, drilling from both sides until they met.)

Thats exactly why I didn't bore it yet. I had assumed that it was the last thing to do after getting everything else right and then, as you say, use the hole in the cam as the guide.

Once again, many thanks for your help and advice.

John

[T. Cotten]

You will want brass sheet to match, John!

I bought my saw and brass from MSC Industrial, but their brass varies occasionally.

Ten degrees aims best over the idle screw. Twelve could very well work, with patience to fit the notch with a jewelers' file and ink.
(Just like fitting a friction disc.)

Why would you bore the pin hole? That's the very very last operation, after assembly, and even Schebler aimed different every time.
(I used the original hole through the cam for a guide, drilling from both sides until they met.)

....Cotten
PS:

... I was wondering why he needs to fix another old carb...

I'm asking myself that a lot lately.

[TechNoir]

Hi Tom, thanks for the info on the disc thickness. I have a 1.0mm slitting saw on its way which is approx 0.039" so it wont be too far off.

I dont have a hone but fortunatly the 1988 build included boring the carb true and it is not too bad so I dont need to hone it.

The Merkel comment was for eric, I was wondering why he needs to fix another old carb.

Today I made a new shaft with the exception of boring the pin hole and cutting the slot. I also started making a new mandrel to cut the disc at a 12 degree angle. It all took longer than it should because I had to unpack and find numerous items of tooling that I had packed away last September.

Once the slitting saw arrives I will be able to make some more progress.

John