Square four clutch

[Brian.Challinor]

Hello, Should a 1952 square 4 have a two plate clutch, or a three plate one.thanks

[keith.mettam]

Brian, from DraganFly's website they state :-
'The clutch fitted to all Ariel models , like the gearbox, is also made by Burman. It is a dry clutch using 2 friction plates on all 350 cc models except the W/NG and all the other models which have 3.'

Hope this helps,
Regards,
Keith Mettam.

[Brian.Challinor]

Thanks,
The reason I ask is because I think that I have a 2 plate basket and a 3 plate centre, these parts came with the boxes of bits.

[pete.collings]

The later SQ4 and Huntmasters had a three plate clutch with four quarter-round inserts rivited to the clutch basket, using a clutch centre with no back lip, thus being in effect a four plate clutch.
It was/still is a standard mod to uprate an existing clutch by filing all the outer tangs off a friction plate, and then filing off the lip at the back of the centre, then placing the modified friction plate at the back of the clutch to bear against the clutch basket. Building up the clutch with the original plates then gives an extra friction surface, so a 2 plate clutch becomes a three plate clutch etc.
Make sure the modified plate is still properly located by the basket and centre, and cannot move and jam the clutch operation.

[Brian.Challinor]

Pete.Will the mod mentioned work with the centre and basket I have, before I start modding.

[ray.tolman]

Hi Brian,
I hope I am not intruding on your conversation here but I saw your post about the clutch and thought these photos may be of assistance.
I had previously posted them on the Yahoo Ariel site but you may not have seen them.

The depth of the clutch basket for the 3 plate clutch is approximately 1 3/16".
Ray

[pete.collings]

Thanks for posting the above photos Ray, it help with the explanation of what can be done. My only remaining clutch centre (worn) in the same dimensions as yours, and was from a 3 plate plus basket rivited inserts type clutch.
I think Brian's centre and basket is from a two plate clutch, although I don't have any parts to measure up and confirm this. I would add that the first time I tried this conversion, I used some old but still servicable parts, in case I got it wrong. As it happens, it worked well, and at the next rebuild I used some good condition parts to repeat the conversion.
As Brian's centre and basket look in good condition, first think through what is needed to be done before getting the files out! You will need at least one extra plain and friction plate, but it helps to have a few more friction plates of varying thicknesses.I would modify the friction plate first, using one with worn tangs but otherwise flat and good. I had used a plate with Ferodo type inserts, but you can also have cork inserts*. The thickness of the plate has to be enough to keep the innermost plain plate sitting on the centre, do some measurement with the modified friction plate in place and the unmodified centre in place and lightly tightened. If all is well, file/machine off the ridge at the back of the centre, and put it back in place. Then assemble the clutch fully, you may need either a slightly longer pushrod or an extra ball bearing in the mainshaft centre. Readjust the clutch arm travel (at the gearbox end) to get a good range of movement, and pull the handlebar clutch lever fully in. The outermost plain and friction plates should still be located in their respective grooves at full clutch travel, if they can move partially or fully out of their grooves if pulled hard up to the pressure plate, then substitute thinner friction plates (or carefully sand down existing plates) until correct location is obtained. Then make the usual adjustments to the clutch before replacing the clutch dome.
It is possible to move the clutch basket outwards slightly by placing a six hole basket tab washer BEHIND the basket, to fit between chainwheel and basket. An old tab will do, but make sure it is flat before fitting. This mod is also useful if the basket has been rubbing against the primary chaincase outer, due to slight misalignment or chainwheel needle roller wear.

This mod works well, but if you have not done it before, spend a lot of time thinking and measuring first, before putting file to any clutch parts. Any additional info on the conversion from other forum members is welcome, in case I have overlooked an important factor, it is a long time since I last did the mod, and the above text is from memory!!

* - I prefer Ferodo inserts for Huntmaster/SQ4 clutches that take more power, but used cork inserts on singles. Other may have different experiences and recommendations. It is much easier to adjust friction plate thickness with cork inserts, and they may have a little more "give" than Ferodo inserts, but can wear more on heavy use.

[Brian.Challinor]

Thanks ,
So my center and the basket are both from a 2 plate clutch. I think I understand the mod described but am I right in thinking the first friction plate (the one that you file the tabs off) is free to rotate against the basket.

[pete.collings]

Based on the dimensions shown in your photos, I would say it is a 2 plate clutch, perhaps someone else would like to confirm this.
I have always filed the tangs off a friction plate to the extent that it can just move freely, this ought to help lessen the backlash between basket and centre and hopefully reduce the rate at which wear notches appear in both basket and centre. If the modified plate is a tight fit, make sure it is in full contact with the inner basket surface and runs true, or you may end up with a dragging clutch.

Given that the clutch will be for a SQ4 (as your initial post suggests), it might be easier to just buy new 3 plate clutch parts if finances allow. I was still a student when I first did the clutch mod, and had some good condition used 2 plate clutch parts, but not much money for purchasing brand new components.

[Brian.Challinor]

I might just build it up as a 2 plate clutch, I wont be fitting a side car or a double seat the only thing that will need altering is the push rod. I'll keep my eye on fleabay for the correct bits, see what comes up.