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MG MGA - Throttle return spring

I am looking at the arrangement for the throttle pedal return spring (LHD car). It pulls back on the fitting where the cable is attached to the lever. Ideally this fitting should swivel as the throttle is opened, to keep the cable straight. The spring action locks it up and prevents this from happening. I am thinking of drilling the lever and installing a separate pin for the spring to pull on. Am I being too fastidious?
Art Pearse

Art,

The engineers that designed Triumph cars shared your concern (see image).
I do not think that it needs a separate pin, just another hole.


Mick


M F Anderson

Art is not being paranoid. I think he is talking about the spring in the passenger side foot well on a LHD car. See item 8 in the attached picture. Also notice the plate with "L" bend and small hole in the ear located between item 10 and item 11. The spring connects from this anchor point to the trunnion item 6, assisting in pedal return. This change was made at (c)24594 in January 1957. See CSM-MG/202 here: http://mgaguru.com/mgtech/care/csm/mg202.pdf
There should be a slightly earlier CSM, MG/197, but I have never found the copy. I suppose that one recommends retrofit to earlier cars.

I have a similar problem with this bit for at least 20 years now. During throttle motion the trunnion wants to rotate along with the lever. This applies a regular back and forth bending action to the cable. Eventually the cable breaks just ahead of the trunnion. With aggressive driving (when I did autocross and TSD rally regularly) this would be 7000 to 10,000 mile intervals. This must be a bit longer with long distance touring, because I did not break a cable during 13,000 mile and 19,000 mile trips in 1989 and 1997.

So far my solution is to tolerate the consequences, I carry a spare throttle cable in the tool kit and change it when it breaks. A quick emergency field fix is to pull out and re-thread the center cable, latching a small locking pliers onto the frayed end at the trunnion aft of the toe board. Last time this happened to me was August 9, 2007, with 10,770 on the odometer, first day out on my way to Pocono, PA. Checking current mileage, my car has another 23,000 miles since then, so I better go take another look at it. With a bit more forethought I could inspect it periodically and change it when it looks a bit frayed before it breaks (like right now maybe).

A better design would be a short piece of steel rod on this end of the cable and matching steel tubing on the firewall. The tube would guide the rod, and the rod would keep the trunnion aligned with the cable axis. Wonderful retrospect 55 years later, but in 1955 it may have added a nickle to to cost of production.



Barney Gaylord

I think that Art's solution should work.
If he drills a hole in the bracket at a point just below the trunnion, attaches the spring there, and greases the trunnion, the bending force should not be applied to the cable.


Mick
M F Anderson

This thread was discussed between 13/08/2010 and 14/08/2010

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