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TOPIC: 8x4 MAZ/MA3 535A from Lunchkins

8x4 MAZ/MA3 535A from Lunchkins 4 months 3 weeks ago #55701

Screenshots from Spintires for future reference ...







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8x4 MAZ/MA3 535A from Lunchkins 4 months 3 weeks ago #55709

Thinking about the cable reel, 50mm diameter is about as big as I can get on the Unimat, and as I don't fancy hand sawing a bar that big I was limited to precut 50mm or 100mm lengths (I couldn't really justify buying a bigger 7x14" lathe and/or bandsaw for just this one piece).

I've come up with a back-of-a-cigarette-packet design (neither particularly square or symetrical :whistle: ), it's fairly chunky as TBH the less I have to take off the billet the better ... however I did worry about how much wire rope (1.5mm diameter Bowden cable) I'd be able to get on the reel, 2.5m being about the amount that seemed a realistic optimum.

I found a hose drum capacity calculator at https://www.copely.com/tools/hose-drum-and-reel-capacity-calculator/ , and plugging in values from my sketch (d = 1.5mm, core = 26, flange = 50, traverse = 32) suggested I'd get 20 to 23 _metres_ of "hose" on my reel.

This seemed a lot, so I wanted to check the maths...

flange - core = 14mm, / 1.5mm = 9 layers
traverse of 30mm / 1.5mm = 20 rounds per layer
core circumference = pi * d, and will go up 3mm per layer
			d	c		
layer	1	3.142	26	81.692	20	1633.84
	2	3.142	29	91.118	20	1822.36
	3	3.142	32	100.544	20	2010.88
	4	3.142	35	109.97	20	2199.4
	5	3.142	38	119.396	20	2387.92
	6	3.142	41	128.822	20	2576.44
	7	3.142	44	138.248	20	2764.96
	8	3.142	47	147.674	20	2953.48
	9	3.142	50	157.1	20	3142
		sum				21491.28 mm

... or 21.49m.

:)




I just have to make it now ...
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Last edit: by Jonny Retro. Reason: typos

8x4 MAZ/MA3 535A from Lunchkins 4 months 3 weeks ago #55725

Had hoped to have started on the winch drum, but the still aluminium hasn't arrived so I made some keepers to help locate & protect the swing bearing on the rear axles, and also started on the boxing in on the underside of the chassis. The rear end has a lot of layers & reinforcement as I'm planning to fit a towing eye in that area :)







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8x4 MAZ/MA3 535A from Lunchkins 4 months 3 weeks ago #55732

Aluminium finally arrived, facing it off went smoothly enough ...



... as did drilling all the way through on the pillar drill. I didn't get very far before the traverse action on the top slide was seizing up. Nothing was obvious from the outside & cleaning & lubing what I could wasn't helping, so I completely dismantled it & cleaned in the U/S tank ...







Back on track, but after several grabs & motor stalls I killed the PSU & speed control. It looks like it's just fuses are the problem, but they are odd types & I can only get them by mail order. I'll probably have it up & running again by the end of next Wednesday, but I've got to question the wisdom of continuing to push the Unimat so obviously beyond its capacity :(

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Last edit: by Jonny Retro.

8x4 MAZ/MA3 535A from Lunchkins 4 months 2 weeks ago #55735

Wow, looking good man!
Ya, that's a big piece of alloy for a unimat and before I had anything bigger I would do such things too. I do recommend you support the free end with a center in the tailstock, It will really help with the digging in problem. And of course take small bites. The mate I sold my old unimat too called me up shortly after he got it because he broke one of the chuck jaws when he did a similar thing turning a longer fat piece of brass unsupported, expensive lesson learned. I think there is an old machinists formula for such things something about 1 1/2 times the diameter and you need to support it, or something like that.
The unimat is very capable, there is a riser kit for turning even bigger stock, folks have built some amazing things with them. :)
Despite their obvious design flaws I am still very much a fan of them, for the price and size it is just amazingly handy to have one :y:
From somewhere out in the wilds of central Ontario.
.......you build what you like, I will build what I like........it's all cool......
 
 
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8x4 MAZ/MA3 535A from Lunchkins 4 months 2 weeks ago #55742

Thanks Oldwilly, I can get a live centre in the tailstock to reach with the current setup, which should at least let me finish the end I'm currently working on ... once I've charged up a couple of batteries. :)

I have the official headstock raising block & made a block to lift the toolpost the same amount, but I'm not aware of anything available to lift the tailstock on the early models :(

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8x4 MAZ/MA3 535A from Lunchkins 4 months 2 weeks ago #55767

One advantage of using Anderson Power Pole connectors ...



Tail support meant I could finish the end I was working on & start digging out the useful bit, however the diameter was too great to get any part of the slide under it, so had to do the rest unsupported. I gave up chasing the flaws as every time I was getting somewhere, it dug in again. Changes from the "design" were counterboring to 8mm so it would fit the gearbox output shaft :whistle: and reducing the depth of the load area. As i've decided to use 1mm wire (for flexibility) it still means the capacity is over 16metres.



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8x4 MAZ/MA3 535A from Lunchkins 4 months 2 weeks ago #55768

Can't order any more parts for a few days, so I thought I'd start on some of the detail bits that aren't dependant on doing anything else first - this is as far as I got yesterday:

(I cheated a bit because the backs won't be seen ;) )




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8x4 MAZ/MA3 535A from Lunchkins 4 months 2 weeks ago #55769

Nice!

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8x4 MAZ/MA3 535A from Lunchkins 4 months 2 weeks ago #55774

Fuses for my DIY Unimat PSU arrived - 20mm, 15A fast blow ceramic (2.93 GBP for 5) & 10mm 6.3A slow blow glass with axial leads that need soldering in (3.20 GBP for 3).

Both types installed & PSU reassembled, lathe working as intended again :)
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