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Jan 31, 2021 13:21:55 GMT
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There is some craziness going on in my garage...... Because I'm fed up with trying make working Triumph gearboxes out of the battered remains of many others (that have been recycled several times already), I'm in the process of trying to fit an NA MX5 gearbox into my GT6 with the original(ish) Triumph 6. This isn't a popular conversion - for which there are several really good reasons. These reasons can be summed up as "it really isn't very easy". Anyhow, I'm at the point where the gearbox bolts up to the engine and sits in the car on fabricated mounts with the gearlever coming out in the original Triumph position. What I don't have yet is any clutch actuation method. This is partly because I'm using the bell housing from an auto box, and partly because previous projects that have mixed and matched parts from both sides have had anomalies in service. The plan is is to use the concentric slave from a Vauxhall Omega. This has a closed length of 50mm and a fully extended length of 72mm, so there is a useful stroke available. Calculation suggests that a .625" master will give 9mm slave travel, with 0.70" and 0.75" giving 11mm and 13mm respectively. The clutch cover will be the usual Triumph 215mm diaphragm, which is basically the same as used on many Fords and Saabs. The friction disc will be an MX5 one. I have a 200mm one to hand in good condition, but there is also a 215mm one available so I'll probably buy one of those. I've been measuring finger positions relative to the engine/BH joint face with and without friction plates fitted so I have a good idea of the engaged positions, but what I can't find is how much stroke is needed on the diaphragm fingers to give full release. ISTR finding spec sheets with this listed in the past but am completely failing to find them again..... Anybody know the answer, or where to find it? TIA Nick Have a pic of the victim  and a Mazda box sat in it  |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Jan 31, 2021 14:48:13 GMT
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Hi, You're most of the way there already, you know the slave stroke so now you need to calculate the lever ratio either side of the pivot point on the clutch release arm.
Colin
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Last Edit: Jan 31, 2021 14:54:10 GMT by colnerov
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Jan 31, 2021 15:21:35 GMT
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Thanks, but the thing is, it's a concentric clutch slave so no levers involved. I'd like to know what stroke the clutch pressure plate needs so that I can: a) determine whether my current 0.625 m/c will produce enough motion (9mm) or if I need a bigger bore master. b) perhaps more importantly I need to set the position of the slave in the bell-housing so it can't be over-stroked. I could take the safe option and assume that I have to allow for up 0.75" master (13mm slave travel), but I really don't have very much space to play with as the bell housing is quite short. 146mm from engine plate to gearbox front face. The fully relaxed clutch needs 77mm from the (probably I don't need quite that much as that is measured with no friction plate at all, but I don't have a worn out one to try) and the bearing cover/oil seal housing/slave adaptor is going to need to be 20mm absolute minimum, leaving 49mm between them, which is already 1mm less than the fully compressed slave! There are shorter concentric slaves available but tend to be odd shaped plastic things with integral release bearings which are too small. Either that or they are from the likes of Tilton or AP - very lovely, but horrifically expensive! Nick    |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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lebowski
Part of things
Hillman Avenger, Clan Clover
Posts: 476
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Jan 31, 2021 15:30:37 GMT
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Nice work. I'd like an mx5 box in my Avenger for the lovely shift, but they only seem to come with a 3.6ish 1st gear, which I already currently have with my type 9, and it's too short.
At some point I'll probably get a taller 1st put in the Ford box.
Sorry, slightly off topic ramblings...
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Jan 31, 2021 16:23:12 GMT
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Hi, You need to carry on and calculate the Triumph arm to see what stroke it gives the Triumph pressure plate fingers and that's what it needs. Once you have that, you need to compare the Triumph master size with the Mazda master cylinder size and see if it's compatible or you need to change it.
HTH
Colin
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Jan 31, 2021 17:56:31 GMT
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I've got a land rover brake master cyl ( 3/4") operating a corsa concentric slave on our minor, but it doesent use the full travel.
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Jan 31, 2021 20:29:15 GMT
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Hi, You need to carry on and calculate the Triumph arm to see what stroke it gives the Triumph pressure plate fingers and that's what it needs. Once you have that, you need to compare the Triumph master size with the Mazda master cylinder size and see if it's compatible or you need to change it. HTH Colin Ah, ok, with you now. Could do that. If I had half a brain I’d have measured the actual strobe at the Triumph slave before I took it to bits! Thanks Nick |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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ferny
Club Retro Rides Member
Posts: 983
Club RR Member Number: 13
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Nick. Might be worth letting you know that I've an Exedy 1.6 clutch kit here which is two years old. Wouldn't hold 200bhp when the turbo came on at Goodwood but was fine other than that. I might even still have the release bearing if you need it for measuring.
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Most clutches don't take much travel to disengage fully. It's quite hard to calculate because it depends on the deflection of the spring. Most clutches I have worked with needed less than 10mm of travel at the release bearing to fully disengage tho.
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Nick. Might be worth letting you know that I've an Exedy 1.6 clutch kit here which is two years old. Wouldn't hold 200bhp when the turbo came on at Goodwood but was fine other than that. I might even still have the release bearing if you need it for measuring. Appreciate the offer Pete. I’m using the Triumph flywheel and pressure plate. I have a 1.6 friction plate and cover which look lightly used. I could use the friction plate with the Triumph cover but it’s 200mm rather than 215mm so I’ve ordered a 1.8 one which is 215mm. It’s only a standard-ish 2L GT6 engine (110bhp / 120lb/ft), so not too challenging in that respect. Nick |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Most clutches don't take much travel to disengage fully. It's quite hard to calculate because it depends on the deflection of the spring. Most clutches I have worked with needed less than 10mm of travel at the release bearing to fully disengage tho. Yeah. I have it in my head it’s about 8mm. I’m a bit frustrated as I’ve previously found data sheets on line that give this kind of information (even thought I’d saved a couple) but can’t find it it now...... Might have to rig up something simple to see if I can measure it. Nick |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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ferny
Club Retro Rides Member
Posts: 983
Club RR Member Number: 13
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Nick. Might be worth letting you know that I've an Exedy 1.6 clutch kit here which is two years old. Wouldn't hold 200bhp when the turbo came on at Goodwood but was fine other than that. I might even still have the release bearing if you need it for measuring. Appreciate the offer Pete. I’m using the Triumph flywheel and pressure plate. I have a 1.6 friction plate and cover which look lightly used. I could use the friction plate with the Triumph cover but it’s 200mm rather than 215mm so I’ve ordered a 1.8 one which is 215mm. It’s only a standard-ish 2L GT6 engine (110bhp / 120lb/ft), so not too challenging in that respect. Nick No worries. I fitted a lightened 1.8 flywheel and went to a hybrid ceramic clutch, so at least you'll have a lot more options later on now. |
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So, just to follow up on this. I've done some more measuring on my spare engine (this gives the measurements I need to the engine/BH mating face) and also removed the flywheel from the engine and assembled the clutch to it before popping it all onto the mill to try and measure the stroke directly. That went surprisingly well, the hardest thing being determining the point at which the friction plate is released as my "rig" didn't leave it very accessible to I was reduced to poking at it with a thin screwdriver through the gaps between the diaphragm fingers. I did the the trial twice. First time with a brand new friction plate measuring 8.4mm uncompressed and second time with the most used friction plate I could find, which measured 7.6mm uncompressed. The new plate gave what felt like full release at 6mm travel and could just be moved at 5.5mm. The old plate gave full release at 5mm travel and could still be just moved at 4mm. Reckon that one is pretty near fully worn. Also of interest was that wear in the second plate moved the fingers rest position 3mm back from the flywheel face. Of course, once I'd done this I promptly found some published numbers in a Helix catalogue and though they don't actually publish the stroke, the disc thickness numbers and change in finger position (they call it clutch set height) with disc wear agreed well so I feel like a I have a reasonable handle on it now. Time to cut metal...... Nick PS. Just in case anyone is interested enough to want the full story here is the build thread on the Sideways Technologies forum sideways-technologies.co.uk/forums/index.php?/topic/8925-mazda-gearboxes/#comments  |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Thanks for updating this, I'm currently working out the clutch release mechanism in my own conversion so this info is pretty handy. Is the Helix info available online, or did you find it in a physical catalogue?
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Thanks for that, lots of useful info in there. Saved it for future bedtime reading!
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