Lemme ask a "hand throttle" question...

Trapdoor2

Trapdoor2

Senior Member
In messing about, learning things, etc., I've noticed that the hand throttle works pretty well up to about halfway...then it gets stiff...and never gives full throttle.

I was astounded to see that the actual connection from the steering column to the whatever-that-Rube Goldberg-mess-is-called-connecting-the-driver's-side-to-the-carb is one of the cruder arrangements I've seen. Just a bent piece of rod pushing on another bent piece of rod. I'm going to dab a bit of grease on the contact surfaces and maybe spray some lube around the other joints.

I have heard that some folks use the hand throttle for a "cruise control". I could get half-throttle, maybe a tad more if I yanked it down hard. I don't think it needs to reach full-throttle...but my Dad always said, "you may not think you need it, but you'll be cussin' when you do!"

Maybe it needs a bit of adjustment?
 
The throttle linkage can and should be calibrated. When the lever at the steering wheel is at the top of its travel, the throttle arm on the carb should be precisely closed, i.e. idle. When the lever is at the bottom of its travel, the throttle arm should be maximally open, i.e. WOT.

If you're not getting that, there are several points to take a look at:
- The control rod linking the arm on the steering column to the bell crank on the throttle control assembly is often bent to correct for some other misalignment. This should be straightened.
- The throttle control assembly is sometimes bent out of shape from having been left attached to the motor as the motor was being removed. This should be corrected or replaced.
- The bell crank on the steering side of the throttle control assembly should be positioned so that the arm of the crank is touching the accelerator pedal arm at all times. Often this assembly is misaligned so that when the hand throttle is at the top of its travel, the bell crank is 1/2 inch or more away from the accelerator pedal arm.
- The long arm on the carb side of the throttle control assembly can be bent carefully by hand to increase or decrease the distance between it and the throttle arm on the carb.
- Original forged steering column lever arms (the small arms at the bottom of the rods) can be bent to adjust the distance in the linkage. Reproduction cast arms cannot. Sometimes you can re-drill the peg hole on the rod if you really need to.
- Lastly, the steering column on 30/31 cars can be rotated to move the lever arm away from the bell crank. (Note that this will affect other spatial arrangements, like the spark advance rod.)
 
Thank you! Just another area that I'll have to work my way thru.

I can see indecent gaps in the linkage. The hand throttle doesn't actually do anything until it is about halfway down, but the foot throttle has just a bit of slack. I don't think any of the rods are bent along their length (they look straight) but I'll have to dig deeper to see what the bitter ends are doing.
 
Ok. Good, clear video. The gap on mine is about 1/4"...and variable. The bell crank is very loose on its pivot, probably from 95yrs of wear. Without taking it apart, I can't tell if it is the bell crank or the pivot that is worn.

The bellcrank lever arm that pushes on the transverse shaft (which goes behind the engine to the passenger side) appears to be bearing too high on the crook of the transverse shaft, resulting in poor leverage/mech. advantage. The transverse shaft is very rough in the contact zone...like rebar. Some judicious polishing would help.

I pulled all the ball & socket actuation shafts, cleaned and oiled them. That helped a little. I can now achieve WOT with the hand throttle...but I'll have to sort out the worn bits eventually.
 
The throttle control assembly is not super hard to remove if you want to mess with it. You remove the front floorboard and there are two bolts attaching it to the engine block.

I was recently talking to someone on another thread who also had a lot of play in his bell crank. I think he said the bore was wallowed out. The diameter of the bell crank post should be .375" if you want to mic it and check. The crank itself is just held on with a cotter pin.

Replacement throttle control assemblies usually run $40-$60 on eBay if you're not particular about getting the version that's correct for your car.
 
have someone in the driver seat move the hand portion down and back up the notches and you inspect all the moving parts down below to see where it's hung up or what may be bent or out-of-alignment. you can also remove the floorboards and get a better view up close of the entire linkage set-up. there's a lot of moving parts that could have been farmer-fixed and unless you have pictures or the judging standard book with you it may be hard to tell what's not correct angles and movement.
 
I looked at the pictures of the progression of design. Clearly my lever arm is bent upwards (besides being worn). It looks like it will bend back like it should...there's a couple on ebay, so I'll see what I can do to fix mine before buying a replacement.

Thanks, y'all!
 
maybe a little heat, not too much, tappa tappa tappa ... gently .... and get a spare just in case ..... good luck
 
Ok, now that I've finally gotten past getting the floorboards out...

Yah, my bellcrank was bent upwards about 20-30 degrees. Now pretty straight. I have a "parrot vice" with thin jaws. That allowed me to get the bent portion in the jaws and squeeze it flat. No big deal.

The holes in my bellcrank are not terrible. It is the shaft that is worn. There's several ways to skin that cat but I decided to do a little judicious "polishing" on the contact surfaces (see pic) and re-install. Cleaned the assembly up while I was at it. New cotter pin.

Reinstalled said assembly and hooked up all the control rods. I added a couple of drops of engine oil to the cups on top, a drop on every control rod end and a little swipe of red grease on the contact area.

Ooooh. Smooooooth. Now I have WOT! Yah, there's still slack in the system. The worn bellcrank shaft means the hand throttle doesn't move anything until it has 4-5 clicks on it. As long as it will allow me full throttle range, I'm good for now.

Ok, back to under the floorboards. Lots of cleaning to do. Gave the throw-out bearing sleeve a short pump of grease and cleaned the cover. Next up is to check the transmission fluid level. The previous owner changed the ****** fluid once (he owned the car 15mo)...and left me a partial jug of 600w oil. I'll check that it's clean and top it up if necessary.
 

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If the bellcrank shaft arm is sufficiently worn, could you fit a sleeve over the shaft (say a sleeve bearing or a coupler fitting) to take up slack? I have the same problem as trapdoor, but my shaft arm has more play than his.
 
Mike1291 said:
If the bellcrank shaft arm is sufficiently worn, could you fit a sleeve over the shaft (say a sleeve bearing or a coupler fitting) to take up slack? I have the same problem as trapdoor, but my shaft arm has more play than his.
Click to expand...
I've been looking thru the McMaster Carr catalog, trying to find a reasonably close bushing to do just that. The bellcrank holes could possibly be opened up to ~7/16"...but the shaft is 3/8", so the wall thickness of the bushing would be pretty thin.

They have some light duty low carbon steel spacers that are .318" ID X 15/32" OD (which is pretty close to 7/16"). They're split like a roll-pin too.

I was thinking I could file down the shaft to fit, push on the bushing and silver-solder it in place.

Alternatively, the shaft could probably be cut off and then the base drilled and tapped for a 3/8" shouldered stud (or even drilled thru and held on with a nut) of appropriate length.
 
Since you oiled the top cups that may help the situation to allow easier function and not GGGGRRRRRRIND the shaft. Maintenance on an "A" never stops......
 
al's28/33 said:
Since you oiled the top cups that may help the situation to allow easier function and not GGGGRRRRRRIND the shaft. Maintenance on an "A" never stops......
Click to expand...

LOL, the learning curve isn't very steep...but it seems like it also never stops!

Anybody out there know what torque to use on the two bolts that hold the throttle linkage to the Trans? They're 7/16", so, using the torque value chart in the back of the "Big Red Book", looks like anywhere from 36-55 for less than grade 8 bolts. I can't make out any markings on the bolts, so I'm thinking 40ft/lbs ought to be fine...?
 
I think the manual throttle was just a hold over from the Model T to keep Henry happy. There really isn't much about it in the operators manual.
 
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