Stromberg OF tip of the day

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Scott_Conger
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Stromberg OF tip of the day

Post by Scott_Conger » Wed May 18, 2022 4:17 pm

When the Stromberg OF was sold to mount in a Model T, it came with a choke control that mounted on the steering column. When you started the car with the starter on a cold day, you simply put it to "Choke" (full "on") and once the car started, you immediately moved the control to rich/run which opened the choke plate from full closed to only partially closed. This is the only richness adjustment available after the initial set-up on the car when the carb is installed.

But what if it was a hand-crank car? How could you set the choke control to full choke, crank the car and then run around to the driver's position quickly enough to ease up on the choke?

Well the answer to that is the choke limiter tab on P/N 8468 Choke Tube Holder. That tab is bent "out" to engage the choke lever and hold the choke open to the rich/run position, and when cranking at the front of the car, the operator pulled the choke wire as normal to over-ride the limiter. That's what the spring in the choke assembly is for! Once the car starts, the operator releases the choke and the choke plate is automatically readjusted back to rich/run and there is no rush to get back to the driver's seat. Nifty!

Now you know why the coil spring is there and maybe you'll want to be sure the tab on YOUR carb is either bent out to engage or bent in to miss the choke lever as would be correct for your car.

Here is the tab bent "in" and the choke is full "on" for starting with a starter (see circled area):
Stromberg OF with choke limiter inactive.png

Here is the tab bent "out", limiting the amount of choke applied from the driver's seat, but can be overcome by the operator in front of the car by pulling the choke wire and energizing the coil spring (see circled area). as an additional note, this carb has the float bowl vent at the top side of the bowl - this carb would have a NON-VENTED float rod nut:
Stromberg OF with choke limiter engaged.png
Scott Conger

Tyranny under the guise of law is still Tyranny

NH Full Flow Float Valves
Obsolete carburetor parts manufactured


Petrah Phyre
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Re: Stromberg OF tip of the day

Post by Petrah Phyre » Wed May 18, 2022 6:16 pm

I have an OF that has the throttle holes and shaft that have seen better days. What is the process for alignment when drilling for new bushings? Can the shaft be 'brazed' and resized, or is it better to just turn out a new one? I really can't believe my T was running with how worn out it is, but I did witness it myself a few years back BM (before mothballed).


Topic author
Scott_Conger
Posts: 6428
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
* REQUIRED* Type and Year of Model Ts owned: '13, '15, '19, '23
Location: Clark, WY
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Re: Stromberg OF tip of the day

Post by Scott_Conger » Wed May 18, 2022 6:35 pm

Fixturing prior to and during machining is key to keeping things in line, with post bush-install ream and sometimes line lapping for a dead-close fit that does not bind.

The wear you found is normal in as-is OFs. The economizer ramp forces are very hard on the throttle shaft, and the original shaft is made from fairly soft brass that is almost certainly 360 brass which as you've found isn't inclined to hold up very well.

I would not be inclined to braze up a shaft ... I simply make new ones when I need them
Throttle Shafts.png
Scott Conger

Tyranny under the guise of law is still Tyranny

NH Full Flow Float Valves
Obsolete carburetor parts manufactured


Allan
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Re: Stromberg OF tip of the day

Post by Allan » Wed May 18, 2022 8:17 pm

Scott, you have tougher me something new again. The last OF I found has a vent hole in the float cover, unlike the one Stan rebuilt for me. Now I need to find an invented acorn nut. Any idea where I might find one?

Allan from down under.


rickd
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Re: Stromberg OF tip of the day

Post by rickd » Wed May 18, 2022 9:18 pm

Well done Scott. Thank you, important info about our Stromberg carbs.

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