Here we have another one of those clever bits that you’ve maybe heard about but never given thought to. Maybe we need a better name… but this linkage will allow one pedal to control two throttles, at any ratio. Useful for woodgas under carb setups.
Max Gasman posted this a few weeks ago:
"Hi, Tyler!
Panic: One gaspedal, One brakepedal on the floor!
Convenience: On dash
common idle adjustment (“handgas”), follows the fuel selector.
woodgas/air fine adjustment
These adjustments will cover “all” your needs…
The gasoline carburettor adjusted without any “own” idle; getting needed idle adjusting through the common idle adjustment. This way no gasoline is used when total woodgas is chosen."
So, I asked Max about it, and he sent me the drawing below (1st pic). I thought I had it figured out, so I decided to build a model from the kid’s LEGOs. Video here, photo below (2nd pic). http://youtu.be/tvQZ15NYSi4
The one thing I haven’t quite figured is how the slider valve can attach to a cable. In my model at least, there’s too much swinging motion to attach anything solidly.
Another drawing of this type of linkage comes from Kurt Johannsen in Australia, many years ago (3rd pic). I don’t think his will work as smoothly as it depends on identical spring rates from the throttles. But he obviously found it worthwhile.
Sean French had a neat mechanism on his 70 kW 3 phase GMC powered generator. I seem to remember two sprockets with a chain drive…(I can’t find that video.) Your LEGO demo reminds me that the windshield wiper assembly fell apart under the cowl of my 1990 Dodge. I have new wiper bushings but it is a bit cool to go out there and crawl up on top of the engine and reach through some itty-bitty slots to put them on…
I don’t know why, but I’m having a hard time seeing a way to make this in metal. I’m not a very creative type and more adaptive.
Assuming I use two identical style of throttle bodies, like say a Holley 94 carburetor for gasoline and the TB base of a Holley 94.
For the Stromberg 97/Holley 94 family of 2BBL carbs they make these auxiliary arms for when people sync them up. You can clock the syncing arms just about however you want, some people set them up to have the carbs progressively open like a mechanical secondary. So these carbs would be a pretty good baseline for the proportioning mechanism like you’ve shown in Lego.
Only way I could see replicating this would maybe use a pull cable with a long distance from the cable housing so it can flex, and have a strong return spring? Could use a really tight lever and motorcycle throttle cable perhaps, and the spring would do all the work for the return action.
That third drawing is too abstract for me to understand. The first sketch and your Lego construction makes way more sense.
It actually isn’t that bad, the levers for the butterfly valves are connected with a rod, if you pull in the center, they open and close at the same time. The pedal connection is floating with like a bushing that rotates on a pivot point, so if you move the cable to the dashboard, it moves the pivot point, and it works like a lever. Put a pencil on the table and push it in the middle and it rolls straight, if you push it near the end, the short side moves further.
I reckon you’d need to fabricate a new intake plenum so the carburetors could sit sideways for this to work(the Kurt Johannsen version) . Or maybe bellcranks.
I’ve watched it dozens of times. Like I wrote, his Lego design makes the most sense I’m just having a hard time figuring out how to make it in metal, and have a reliable cable setup to go between modes.
I would poke around the hot rod forums. Because if you have a 2+2 or a 4+4 set up, and you want to cruise around looking for a street drag, you might want to switch from the factory progressive mode to race mode with the pull of a lever. So you get the better fuel mileage while cruising for a race. without have to spend 2 hours tuning it…
I still think Chris’ and Max Gasman’s linkage is the smoothest idea so far to do true blending without too much proprietary fabrication. A lot of Chris’ idea can be done with off the shelf rods with clevises or little tie rod ends. My only mental hurdle is the way to connect it to a pull cable or lever and stay smooth.
probably use a hollow tube for the part that turns with the accelerator. then put a slot in the tube for the linkage, and have the cable connect to a ‘piston’ in the tube, that is connected to the linkage, and you may need a simple swivel to connet the piston and the cable.
You might be able to skip the ‘piston’ and put a slot in the linkage, connect the cable swivel to the linkage and have a pin on the outside that acts as a moving pivot point, that the linkage can travel.
