Alfa power build.

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ChrisS
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Re: Alfa power build.

Postby ChrisS » 14 Nov 2017, 13:32

By coincidence, I've just reached the same place as Eric has in his build. Rear suspension subframes etc all done now, lower rear wishbones still need finishing but I was keen to do the basics today and get the rear upright in place for a look-see. I want to get the dimensions for the drive shafts sorted out as soon as I can, as I suspect there will be a long lead time on them. Not that it'll be an issue as such.

This feels like a stupid question, but I'll ask it anyway - not like it'll be my first or likely last stupid question either.

So, rear upright, I'm assuming(!) that it is intended that the lower pivot axis is horizontal. Just throwing the assembly in place and mine isn't at the moment. I ran out of time to mess with it but expect I can bring it square with some adjustments of the upper & lower wishbones.

Couple of pictures:

Alway interesting how lens angle etc can make something look very different. Lower wishbone is almost perfectly parallel with the lower chassis rail at the moment - certainly doesn't look like it in these shots.

Left rear 1.jpeg


Left rear 2.jpeg
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Midlana1
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Re: Alfa power build.

Postby Midlana1 » 14 Nov 2017, 14:24

Short answer: it doesn't really matter much. Without looking, I seem to recall the upright being tilted back a little. Don't worry about it.

ShadowCat38
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Re: Alfa power build.

Postby ShadowCat38 » 14 Nov 2017, 18:25

We may be at the same point of the build right now, but you reached this point in what... 5 months? I've been at this for 2 years, granted a few months of that was the engine overhaul. Still, seeing you catch up and likely blow past me is part of the reason I'm back on here and getting back to it. My break-time has lasted long enough. Thanks for the kick-in-the-pants! I'm going! I'm going! :D

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Re: Alfa power build.

Postby ChrisS » 15 Nov 2017, 02:11

Midlana1 wrote:Short answer: it doesn't really matter much. Without looking, I seem to recall the upright being tilted back a little. Don't worry about it.


Thanks Kurt - I'll concentrate on getting the camber, toe & absolute position correct.

Apropos the rear uprights, I'm not totally happy with my decision to use polyurethane bushes at the top now - they constrain the movement totally to the one axis which I can foresee being a potential issue, at least during setup if not use, so I'm pondering on either going back to the book method, or possibly replacing the outer clevis with a rod end so the forward leg can rotate a wee bit as needed. I'll see how I feel about it after messing with the setup first - might not be an issue.

I noticed that the OEM rubber bush has a somewhat ovoid shape to it which I assume was to allow a small amount of movement along that plane?? This aftermarket bushes wouldn't allow any, being pretty hard (feels like Shore 90) and cylindrical.
Last edited by ChrisS on 15 Nov 2017, 02:22, edited 1 time in total.

ChrisS
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Re: Alfa power build.

Postby ChrisS » 15 Nov 2017, 02:17

ShadowCat38 wrote:We may be at the same point of the build right now, but you reached this point in what... 5 months? I've been at this for 2 years, granted a few months of that was the engine overhaul. Still, seeing you catch up and likely blow past me is part of the reason I'm back on here and getting back to it. My break-time has lasted long enough. Thanks for the kick-in-the-pants! I'm going! I'm going! :D


I've only really been doing the actual construction phase for 5 months, but I was gathering parts and doing prep work long before that. I am aware how lucky I am to be retired and able to spend as long as I want on it though. I honestly don't think I could have done this if I'd still been working full time though. Having already done 2 previous kit builds where funds & time forced long timescales, I certainly wouldn't embark on one like this, so all you guys who are still working for a living while doing this have my greatest respect. Or should that be sympathies ;)

Happy to be any kind of positive influence :D Keep up the good work Eric.

ChrisS
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Re: Alfa power build.

Postby ChrisS » 20 Nov 2017, 01:56

Nothing dramatic or picture-worthy, but after some fiddling, I concluded that yes indeed, Kurt's method for the rear upright top mount was by far the best - who knew :)

I mocked one up using a bearing that almost but didn't quite fit properly (a COM10-12T), just to test. I'd bought a couple on the off-chance they might fit into the upright but the OD was just over 1mm too small. Could have shimmed it somehow I suppose, but it all started to get a bit iffy so decided to stick with the bearing cup idea. Thanks to a kind volunteer, I had the two McGill COM10 bearing cups turned down 1mm on the OD so they fit the loop. Made up some spacers from 38mm OD CDS (DOM), welded the spacers to the cups, gently linished the assemblies then pressed them into the loops. Last step was to seam weld all the way round the outer ends. I didn't tack them, as if the bearing needs replacement, it's a simple job to remove the circlip that holds it in the cup. I put the circlip to the front - the reaction force when braking will then be working against the lip of the cup, not the circlip, same as on the lower wishbone forward cup which has the circlip to the front as well, but that's attached to the car, not the upright. I'll be bonding the bearings in anyway, but it doesn't hurt to be safe.

Did a quick trial assembly again yesterday and it's looking way better - so much easier to get everything nicely lined up where it should be when you aren't fighting that constraint of the upper wishbone.

So, to anyone considering using the OEM top mount, or worse, an aftermarket poly one like I did....I'd strongly suggest, don't!

Rear damper mounts next.....

(edited to correct what I put about the circlip locations. I did it right, but reported it wrong. Thankfully it was that way round....)

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Re: Alfa power build.

Postby ChrisS » 22 Nov 2017, 02:11

Bit more done yesterday. Nothing dramatic, just made and tacked the lower damper mounts onto the rear wishbones and made a start on the upper bracket.

Rear damper side view.jpeg
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Re: Alfa power build.

Postby ChrisS » 26 Nov 2017, 01:41

It struck me yesterday as I was working on the right side upper damper mount....that was the last piece that required critical positioning.

So, upper damper mounting structure.

First step was to add some vertical tubes to link the 3 longitudinal tubes. 1.5" round seemed to fit the bill. These were placed vertically above the centre of the lower damper mount when the suspension is at ride height.

Damper mount main tubes.jpeg


Damper location.jpeg


Then the actual mount tube and a brace. Wasn't quite sure which way to go with this, but in the end, I had more of the square tube than the plate so that decided me.

Basic structure.jpeg


And finally some plating both sides to add a bit more strength. The three holes are to plug-weld the plate to the short brace tube. Could have slotted it instead actually and welded all the way along. Still might when I get to the finish-welding.

plated.jpeg



Right side is almost done too - just need to trim the plates and fit them.
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freakynami
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Re: Alfa power build.

Postby freakynami » 26 Nov 2017, 02:25

I've been leaving that upper mount out of my CAD so far waiting for a clean solution to present itself, I think it just did! I like the look of that. :D

ShadowCat38
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Re: Alfa power build.

Postby ShadowCat38 » 26 Nov 2017, 05:02

I've got some clearance issues with Engine mounts, but I like the look of your solution. I'll try something along these lines when I actually have the dampers I'm going to use. Thanks for sharing!


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