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260DET

The Z31 Project - Race Car

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Hi Richard, Just looking at the wheel spacers and realised that they are not hub centric. No support for the wheel that I can see. Only the studs for support. Is this just temporary to measure wheel offsets or a miscalculation. I have been watching the build with interest.

Regards

David

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Well spotted David, a bit of a story there. The Z31's hubs have a step which means a aftermarket wheel which has just a taper will not fit up tight to the hub. If I had got hub centric spacers the wheels then likewise they would not fit properly. But I don't think when using tapered wheel nut's they have to be hub centric anyway because the taper on the nuts means that the wheel studs take the load, the centric flange is not a tight fit so in effect it does not locate the wheel.

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The wheel studs are not supposed to take the load, that's what the hub is designed for. With only the studs you have the chance of shearing them off with loads on the wheel. Dangerous on the road, suicidal on the race track.

Time for a rethink Richard. Play safe.

Regards

David.

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Most of the aftermarket wheels have larger and varying centre bore, so most of the time they don't rest on the hub.

 

I'm with Richard on this one.

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Yes, typically the stepped hub ring is a loose fit and does nothing much at all. In contrast the steering arm to strut bottom interface has a stepped fit which locates the two together, there the two retaining bolts just hold the two together and provide a clamping force but they don't locate the two parts. Two similar looking interfaces but different in the detail, I love this sort of stuff :)

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RLY240 is correct. The load is taken up by the friction between the wheel face and the hub face.

That is why the torque of the studs is so important.

 

Rear end is looking good Richard. Interesting to hear how it performs

Edited by lampy

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By eye, straight edge, tape measure and a few other things the rear end is looking ball park aligned. With adjustment to spare. Only BMW did that type of rear suspension in it's pure form like mine is ie they did not use the drive shafts as top links. I don't know why BMW changed to other types later on because apparently it was a good handler, I suspect factory alignment complications/time and manufacturing costs, some adjustments change two alignments so it can get complicated.

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Doors, big heavy long doors. Make f'glass copies or gut 'em? As usual there is no info around on the Z31, my thoughts were that f'glass ones would be a hell of a job and perhaps the time and cost would be better directed elsewhere. That turned out to be the right decision, one bare door weighed 22kg, gutted just 9kg, happy days! Then there is further weight to be saved, fixed plastic windows with sliders cut into them to replace the glass, plus delete all the electric winder stuff.

 

Pics, working out how to get the intrusion bar out, the bits removed pile and the gutted door itself.

 

post-101215-0-05998100-1505011550_thumb.jpg post-101215-0-14263900-1505011582_thumb.jpg post-101215-0-62353800-1505011604_thumb.jpg

Edited by 260DET

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Intrusion bar in the door has been removed Jason, any intrusion will be taken care of by the CAMS spec cage and, maybe, foam in the doors. 

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The wording was "intrusion bar"

Although these days, it tends to be more a X bar, running from main hoop, to lower forward leg.

On LH side, not required

While you've got the foam'o'fill on the go, do the sill cavities.

Used to do the Dato 1600 rally cars, made a fair difference when sliding into cut down tree stumps.

 

Thought he said doors were 22kg, now down to 9kg, ie 13kg per door weight off

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Intrusion bar in the door weighs about 8kg hmd.

 

Jason, cage will be the same both sides, I wouldn't want to risk peculiar handling due to one side being stiffer than the other. 

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Getting there, been doing some fibreglass work including a mould for a bonnet and two infills for the targa tops, they will be bonded in when the cage is done. Before the cage can be done I have to finish double spot welding the door openings which is proving a bit tricky. For the welds to stick the welder has to be held steady, it's a heavy bloody thing and one hand is needed to work it while the other has to support it and keep it still. A bit much so a counter weighted pulley support using the engine crane has been made as well as a side handle for the welder so it can be neutrally supported and held at the right angle. Welds are good now but some done before will have to be redone, the welder was moving during the welding process.

 

The other structural thing is a removable radiator upper support panel to make engine fitting easier and incidentially stiffen the panel, three bolts each end. Pics of it and the spot welder setup below.

 

 

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post-101215-0-26952700-1507184479_thumb.jpg

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Both door openings have been double spot welded so she is now ready to be caged which should be done this month. Meanwhile there are wheel clearance problems at the front, who was the smarty who said 18 x 10" wheels were the go for the front, eh. See the pics, the black brace behind the wheel is the culprit, not by much but enough, The rim inside clears the spring by 10mm, nice.

 

post-101215-0-01913600-1507621412_thumb.jpgpost-101215-0-30797700-1507621382_thumb.jpgpost-101215-0-76129900-1507621434_thumb.jpg

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Another parcel received, another few thousand $. This is the Gear Vendors overdrive kit for the intended two speed Powerglide, it's mechanical not hydraulic so can go behind a manual box too, it effectively doubles the number of gears of the main transmission. The next thing to be done is to send it to the chosen Powerglide builder so that it can all be assembled together as one unit. Then it has to be worked out how to shift in all gears with a single electric switching sequential lever. Anyway, pic.

 

post-101215-0-34241700-1508386503_thumb.jpg

 

 

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Cool, do they offer a variety of ratios? If so how do you pick the one you want?

Interesting drive coupling from box to OD unit.

Who you gonna get to build it all up?

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Just one ratio, it's about .75 which is fine for mine. Yeh the coupling is splined both ends and is blanked off in the middle to keep it in place, I was thinking about drilling a small hole through the blanking off piece to aid lubrication of the splines but that's probably overkill? The bloke in Warwick who does some of my work will get the Glide done by a specialist, he's a racer with lots of experience with autos and knows what's needed.

 

One thing I hadn't realised until now was that this setup is going to help weight distribution as well as being a much lighter setup than the 4L90E in the 280ZX, the overdrive unit itself will end up a third way down the transmission tunnel. Nice short tailshaft too which is always good.

Edited by 260DET

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So your shift will go:

1

1+

2

2+

With the OD unit switching on or off for every shift?

Is it designed to do that?

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That's the sequence Cozza and that's how it's designed to operate. The switching is yet to be sorted but I have a kit that shifts the Glide electrically so that's a good start, the GV shifts electrically too. Only catch is that the GV is not supposed to be used for engine braking, at this stage I don't know how much engine braking the Glide will give so it's all a bit of an unknown right now. But in any case the project is going to have big brakes so engine braking will not be relied on for outright retardation although engine braking alone can be useful in certain situations of course.

 

Oh and that coupling you mentioned, machined from one lump of steel, cool eh.

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Removed the targa top inserts from the moulds, they were moulded directly off the glass T tops to give a smooth interior surface as the outside has to be finished to blend in anyway. Trimmed them up and in all modesty they are ace, light yet rigid. After gluing them in the tops will be blended in using a light weight filler I'll make up myself. Any glue recommendations?

 

Car is still waiting to get the cage done but waiting for this is apparently traditional anyway. Have started to prepare the bonnet mould, making a bonnet incorporating big vents is the next big job, then the front spoiler which will involve some extensive plastic surgery. Anyway, pics of the top inserts.

 

post-101215-0-99293800-1508989986_thumb.jpgpost-101215-0-16570800-1508990028_thumb.jpg

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To glue the targa tops in I would use sikaflex, whichever one that the perspex mob I bought my window kit from recommends.

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My thinking is that a flexible adhesive may lead to cracking of the filler used to blend the tops into the body work. Bunnings list lots of Sika products, Super Grip 30 Minute Adhesive seems to tick the boxes, has anyone used it?

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