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 N and P type control rods
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Pards

Australia
30 Posts

Posted - 31/07/2020 :  23:18:41  Show Profile
I need to make up the Mixture/Slow Running control rods for my P and N types and would like information on the length of the rods, the diameter of the rods and the thread used. On the later I see on the forum that some have mentioned 2BA thread but to me that felt a bit loose with the knobs I have they appear to be more 3/16"BSF?? As neither car came with the rods I don't know if the two cars share exactly the same rods or if there is a difference. Also does one use a locking nut in combination with the knob on the rods?? Any information and possibly a diagram would prove very helpful.

Bruce Sutherland

United Kingdom
1073 Posts

Posted - 01/08/2020 :  18:00:36  Show Profile
Ian,
This may help:




Control knobs, rods, and rubber grommets should be available from:
http://www.vintagemgparts.com/control_knobs.html

Bruce. (PB0564)

Edited by - Bruce Sutherland on 01/08/2020 18:24:09
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Pards

Australia
30 Posts

Posted - 01/08/2020 :  23:06:25  Show Profile
Hi Bruce,

Many thanks for your assistance - just what I was hoping for. I did try Rich for the rods but he was out of stock. Can anyone confirm if the rods in Bruce's picture are the same for an N type? Also does one use a locking nut in combination with the knob on the rods?? Again many thanks for your help Bruce.

Cheers Ian
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Westbury

United Kingdom
975 Posts

Posted - 02/08/2020 :  08:22:03  Show Profile
Hello Ian.

There should be a locking nut used in conjunction with the control knobs.

Hope that helps.

Chris

Edited by - Westbury on 02/08/2020 08:22:56
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Pards

Australia
30 Posts

Posted - 02/08/2020 :  11:00:09  Show Profile
Hi Chris,

Many thanks for your input. Much appreciated.

Cheers Ian
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Gerhard Maier

Germany
697 Posts

Posted - 02/08/2020 :  17:10:13  Show Profile
Ian,
I can confirm Bruce dimensions for both rods, and also chrome-plated.

And a locking nut - - Yes !
If 2BA or 3/16"BSF, can't tell, as both fits similar ?

One thing which puzzles me, is that the idle adjusting rod which I measured, has a similar thickened threaded end as on the photo of Bruce.
Was that a repair for the worn out thread, or is that original ??
Gerhard


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Pards

Australia
30 Posts

Posted - 03/08/2020 :  06:13:22  Show Profile
Hi Gerhard,

With regard the idle adjusting rod if the thread that goes into the bracket per your photo above is 0BA then I take it the small rod section shown must have a diameter around 11mm yes? Is the bracket also meant to be 0BA threaded or does the rod simply pass through the bracket thus becoming a support to the rod? Would I be right in suggesting the threaded area on the 0BA rod is around 20mm? The bracket on my N type is home made and has a 1/4"NC threaded nut welded to it on the rod side hence the source of my queries.

Cheers Ian
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Bruce Sutherland

United Kingdom
1073 Posts

Posted - 03/08/2020 :  09:49:50  Show Profile
Ian,
The rods at 3/16" dia = 4.7625 mm dia, and their control knob ends are 2BA which has a thread major dia = 4.7 mm dia.

The idle speed rod larger diameter threaded end is 0BA which has a thread major diameter = 6 mm dia.

My idle speed rod is quite badly corroded/rust-pitted, but the little remaining chrome plate finish adjacent to the 0BA section appears over the welded junction between the two diameters, suggesting that this was the original manufacture ...... I think!?

Bruce. (PB0564)
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Gerhard Maier

Germany
697 Posts

Posted - 03/08/2020 :  11:11:20  Show Profile
Ian,
my thickened threaded end (ca 8mm thick) on the slow-running rod, shown in my previous post is 65mm long and has a 5/16 BSF thread 1 inch long.

But I think our discussion about that thickened threaded end is misleading, and that it is a replacement repair for the original worn-out 2BA or 3/16"BSF thread.
On the photo below, both ends of the slow-running rod appear to look the same.
What is not visible on the photo below is an additional spring for the slow-running control rod. That spring is mentioned in the parts list text, and leans against the bracket for the slow-running rod.
Gerhard


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tholden

United Kingdom
1296 Posts

Posted - 03/08/2020 :  11:59:46  Show Profile
Certainly as far as J2's are concerned the 2BA thread in that bracket is very often worn out. I have seen them repaired with a larger diameter of rod as per the picture above, or welded and re cut or with a not brazed on the back. I would therefore suspect the rod in the picture has been repaired unless the factory did this modification during P type production.
On the J2 the rod is tensioned with a washer then a spring and then another washer held in place with a split pin. And yes they were originally chrome plated.

TH
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Pards

Australia
30 Posts

Posted - 03/08/2020 :  14:23:38  Show Profile
Hi Guys,

Many thanks again to all for your input. It seems to me from your responses that the general thrust is the idle adjusting rod would originally have been the one diameter all the way along be that 2BA or 3/16th however wear over the years has led to modifications being called upon. The bracket would have had the same thread as the rod and again this may have led to modifications to match the rod. I assume, as no-one has stated otherwise, that the P and N control rods are the same lengths. If someone has some photos of the washer and spring arrangement on the slow running control rod it would certainly be appreciated. Apologies Bruce and Gerhard - I used Google for the 0BA conversion to mm and it gave a figure of 10.4mm which seemed ...well strange being twice as thick as the rod... hence my query! Again thanks to all.

Cheers Ian
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Gerhard Maier

Germany
697 Posts

Posted - 03/08/2020 :  15:47:51  Show Profile
quote:
Originally posted by Pards

If someone has some photos of the washer and spring arrangement on the slow running control rod it would certainly be appreciated.

Hello Ian,
here is a photo of how that "spring arrangement" looks in NA0468.
Gerhard - - (sorry should have cleaned the area before taking a photo!)


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Bruce Sutherland

United Kingdom
1073 Posts

Posted - 03/08/2020 :  15:59:38  Show Profile
Ian,
To your question ...."If someone has some photos of the washer and spring arrangement on the slow running control rod it would certainly be appreciated."
Here is an enlarged and bit blurred photo of a friend's restored PA idle speed rod (original diameter 3/16" throughout) showing a spring in mild compression and it's washer abutment round the rod. Purpose: to 'hold' the same idle speed setting against any tendency to rotate under engine/gearbox vibration whilst running.





Gerhard, you beat me to it!

Bruce. (PB0564)

Edited by - Bruce Sutherland on 03/08/2020 16:02:15
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Pards

Australia
30 Posts

Posted - 03/08/2020 :  23:11:34  Show Profile
Hi Guys,

Many thanks for all your help with photos and descriptions.

Cheers Ian
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Colin McLachlan

United Kingdom
916 Posts

Posted - 04/08/2020 :  09:20:37  Show Profile
Instead of the spring, you can put a gentle bend on the rod, which then causes it to bind slightly, preventing it vibrating round.

Colin

Crail, Fife.
PA 0613
MG3242
Register No. 2591
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