Author Topic: What do you do when you're given some 1.25" aluminium Hex bar  (Read 1975 times)

Offline Joules

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The only thing I could think of for hex bar.

It really just started as a way of testing the accuracy of my collet blocks and a deeper learning of the DRO on my mill.  Work has dried up and I was given the bar to have a play.   I didn't get any pictures early on as I was just having a play and didn't think it would come to much.  I only did a CAD drawing of the crankcase once I got to the point of boring it out.  About 30 mins to draw in CAD and then the rest of the day making this and one other I cocked up earlier when I got distracted and forgot the allowance for my parting tool.   So I have a second crankcase shell, just 2mm shorter !!!

I will get to use the Turnado for making the front cover, it initially looked like it would become a solenoid engine, but as the cylinders can be swapped out it could also be compressed air with poppet valves, or just a desktop model with an electric motor inside it.   Just having a play about and learning to use the tools I have.
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Offline SwarfnStuff

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #1 on: April 21, 2020, 01:11:24 AM »
Jolly good, now we await the story of how it becomes whatever you decide to turn it into. New tools / toys definitely need playing with.
All the best,
John B
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Offline awemawson

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #2 on: April 21, 2020, 02:13:38 AM »
That crank case is crying out for hexagonal barrels and hexagonal pistons  :lol:
Andrew Mawson
East Sussex

Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #3 on: April 21, 2020, 06:22:58 AM »
Quite a coincidence Joe posting in tools about his 12 sided "Hex" blocks.   I ran into the exact problem he relates too doing the crankcase.  The hex blocks gripped by the faces in the mill vice resting on the hex edges, that are rounded.   What I hadn't realised was the 0.2mm error across those edges.

So how to measure the faces of my little crankcase relative to the internal bore.   I got a set of thread measuring wires a few weeks back, something I should have bought along time ago.  But you can use them for so much more, they are very accurately ground.  In my example 2 wires fitted in a cheap Aldi adjustable vice support the internal bore of the crankcase, the wires chosen fit within the anvil of my mic, they will also average out any burr on the internal edge of my cylinder bore.   I am not measuring the thickness of the crankcase, just the difference between faces.  I would need to work out tangents and loads of maths to do that (too lazy, life's too short)

The mic is gently placed over the face and wires and lightly wiggled to set the wires and crankcase.  Write down the readings and find your lowest face, that is now the reference.  I have 0.005" to come off face 5 and 0.002" to come off face 1

And a little further CAD down this rabbit hole.

« Last Edit: April 21, 2020, 04:15:52 PM by Joules »
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #4 on: April 21, 2020, 05:34:14 PM »
I think my cylinder design is now finalised, I made this test cylinder in Delrin this evening.  The thing is tiny, black and a bugger to photograph.  It still has another 3 operations to finish.  The fins need cutting, trimming the flats on the flange and exhaust ports opening.  As this is Delrin I opted to bore it 1mm undersize.  I might make another in white Delrin to make sure my procedure is sound.  It has an overall length of 14mm, the flange is 1mm thick.
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Offline Pete49

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #5 on: April 21, 2020, 11:19:35 PM »
watching this with  :beer: and sausage. isolation is getting me :lol:
oops..........oh no.........blast now I need to redo it

Offline AdeV

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #6 on: April 22, 2020, 03:37:24 AM »
Speaking of things to do during the lockdown (and apologies for the thread hi-jack):










Cheers!
Ade.
--
Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #7 on: April 22, 2020, 03:46:27 AM »
 :lol:

Cheers Ade, just tried that with the oil jug, don't think I will get rid of the taste till after quarantine.
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #8 on: April 22, 2020, 07:38:54 AM »
Got an early start and put another 6hrs into roughing out 7 cylinders.   Need to take a break and think about the tooling jig to machine these cylinders on.   One spare cylinder for luck...

Having slept dreaming about these things, I skipped another Delrin part as I came up with a better sequence to machine these off the bar.
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Offline Brass_Machine

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #9 on: April 22, 2020, 09:53:50 PM »
Very Nice!
Science is fun.

We're all mad here. I'm mad. You're mad.

Offline SwarfnStuff

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #10 on: April 23, 2020, 12:33:22 AM »
Still looking great Joules, even down here in OZ.
Will follow with interest.   :clap:
John B
Converting good metal into swarf sometimes ending up with something useful. ;-)

Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #11 on: April 23, 2020, 11:11:45 AM »
Thanks for the encouragement everyone.  It makes a big difference being able to do this without work interruptions  :clap:   I wouldn't normally contemplate something like this.

The cylinder mandrel came together in about 20 minutes, so much for a couple of days thinking about it.  So I set too and tested it with the Delrin cylinder, the fins for this cylinder are 0.5mm thick with a 0.5mm spacing.  I had planned to grind up a Stanley blade to make the parting tool, but found a 0.5mm slitting saw.  That was used in my 2MT tool post fixture as a multi blade parting tool.

Sadly the only way to photograph the Delrin is by over exposure, no fancy lighting here.  I did use a macro lens on the phone for the close up.   A little bit of aprehention when it comes to doing the brass cylinders, at least I have enough tips on the slitting saw to more than cover one tip per cylinder.

Still not found my stash of M2 fasteners, hoarded from hard drives and dead laptops over the years.

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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #12 on: April 26, 2020, 04:29:40 PM »
Itís been a long day, but got my 6 brass cylinders machined externally.  I needed to make a split clamp to hold my ER32 collet block directly on the mill table.   This was the most accurate way to register the mandrel for all the cylinders to be drilled and tapped before transferring the mandrel onto the lathe for turning.

I used up some of my luck with the spare cylinder, and messed up one fin.   The cylinder is OK for the rest of the processes and it has volunteered to go first.   Lots more designing and making to do for this little engine.
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Offline SwarfnStuff

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #13 on: April 27, 2020, 12:58:39 AM »
Still interesting so please keep doing stuff. I really want to see this running some day.
Watching with interest.
John B  :nrocks:
Converting good metal into swarf sometimes ending up with something useful. ;-)

Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #14 on: April 28, 2020, 09:32:20 AM »
A little bit of progress yesterday, getting the cylinder flange edges squared.  I had intended to use my mandrel for these, but didn't have the reach with my small cutter, so they sat in Vee blocks with not the best clamping method, as they still needed a finger to stop them lifting from the up spiral of the cutter.  I had to be very careful clamping them lightly to not distort things, hence boring to size will be the last operation on these cylinders.

Today is back at the CAD, getting the big end arrangement and con rods done.  It all has to be tested for fit and clearance, I have tried a number of con rod permutations and still not happy, but this drawing is getting close.  I took a punt on some cheap M2 bolts, they should be here in a week or so, I will check and test them before using on the engine to make sure the quality, is good enough !!!

Also on the todo list is a set of test pistons, they will be to check the motion, set the machining jig and set my stroke clearance, before commiting to the more complex, final parts.


LOL John B, you and me both.
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Offline SwarfnStuff

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #15 on: April 29, 2020, 01:12:48 AM »
Hi Joules,
       I do like looking at what you are doing and reckon it is a real challenge to get 6 con-rods and crank playing nicely together. Specially as you are designing on the fly.

     Heck, I'm currently struggling with a single cylinder model that even after boring and taking several spring passes is still tight at the inner (Blind) end of said cylinder let alone six of em.
     Keeps me amused during this virus enforced stay home or else problem.
John B
Converting good metal into swarf sometimes ending up with something useful. ;-)

Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #16 on: April 29, 2020, 01:36:13 AM »
Ahh, you see John thatís the advantage of never having designed or built anything like this.   You donít know the limitations till you hit them.  It will probably be that each cylinder will need numbering and have a matching piston.  I am leaving wiggle room in the design for parts to find there own positions, that too could translate to vibration and rapid wear of parts.  I am enjoying the challenge of machining the parts as it is demanding at this level.

Good luck with your build.
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #17 on: April 29, 2020, 02:48:03 PM »
You know when you make an "EPIC" spacer, a career defining spacer and drop it !!!

Well this wasn't it, but I did drop it...   :bang:   However on this occasion I found it round the back of the lathe.

I made a start, for want of a better word, on my con rod spider.   I went with brass as the con rods are going to be brass so they stand a better chance with the gudgeon pins. The stock for the spider was machined to size, drilled and reamed before turning and parting off each half.  It was then back over to the mill for more DRO bolt circle drilling.  I used the square ER32 collet block again, the picture below shows the split bush used to pull the block down to the table.   I then spent a happy 45 minutes trying to get the now back to back, spider halves level.   I had made a Delrin stand off to support the discs in the collet, I should probably have made a mandrel to support them, and then bolted them to it.  As it was a one time job I thought I could bodge it, only the 1mm holes are critical.  That was just as well, as when I drilled the 2.8mm holes the top disc pulled out the collet and was spinning on the drill bit !!!  First hole, luckily I was able to slide the disc back into the collet using the drill as a guide and nip the nut up a little more, that will have thrown my carefully got centre.  These are just holes for lightening the spider, unlike the 1mm holes which will be locators for the gudgeon pins, they are clamped between the two halves.

I have a couple of used flanged bearings left over from model helicopter flying (loose term)  The spacer seats the bearing outer and acts as a guide to keep the spider concentric.  The last image gives you some scale to the spider when fitted in the crankcase.   At this point I have pretty much caught up on my CAD progress so far.  I am looking into making the gudgeon pins, be they turned or ground on the ends.  Another jig to make for machining the con rods, and the fun job of making and securing the fixed rod that guides the spider round.   Like eating an elephant, one bite at a time.
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Offline SwarfnStuff

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #18 on: April 30, 2020, 01:02:16 AM »
Pretty sure Rolls-Royce were individual cylinders and matching pistons - before mass production.
   
     Plus a chap here in OZ made a Model Tiger tank and if memory serves me they had 12 cylinders, all of his were made with matching pistons so you are in good company.

   John B
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #19 on: April 30, 2020, 08:55:35 AM »
My M2 bolts arrived, I can finally bolt on the cylinders and take some measurements.  You may recall way back, the crankcase was the project.  It meant I didn't apply the same precision to it I have applied to later parts.   Here is where I find my errors and the play in my setup.  The crankcase was drilled though in three hits, so the opposing cylinder pairs should be inline.  The bolt holes for the cylinders had to be drilled and tapped per cylinder, and this is where errors crept in that I thought I would be able to ignore, cause I'm never going to build this !!!

All bar one bolt circle on the crankcase was within tolerance.  The out of tolerance bolt circle needed some needle file work on the cylinder mounting holes.  All the cylinders have one orientation, I can't turn them 180 degree, so something was amiss in my hole drilling to cylinder centre.  Each cylinder has had to be marked and corresponding marks within the crankcase define position and direction when the parts need disassembling.  I then checked cylinder pair alignment using the 6.5mm drill used on the cylinders.  I am good to a thou or so inline, the cylinder with the out of tolerance bolt circle had the most drag.  The cylinders will be bored out to 7mm and the intention is to do them on the crankcase in pairs, that way I can correct the worst case pair out by 0.003"  That is well within my 0.010" tolerance on the spider, however the closer I get it, other cumulative errors aren't going to nudge me out of tolerance.

Not a lot to show for today other than screwing it together and learning how much the mill can flex and bend at the tool.  Basically, everything I set out to learn and figure how to work round the limitations.

John, I had the pleasure a couple of years ago of getting some hands on with a stripped down vintage Rolls engine.  It was a fantastic experience and I learned a lot about the workmanship of that time, a once in a lifetime opportunity.
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #20 on: May 03, 2020, 11:08:07 AM »
Much doodling and thinking about how to do further parts, curiosity got the better of me.   I made another spider in aluminium to see what the weight difference was.

The brass came in at 4.57gm and the aluminium one at 1.77gm.   Iím guessing I will need to make two crankshafts to try the different weights.

I also had a think about my cylinder bores, I canít correct the 0.003Ē error as it will impact on the cylinder head fixings I have already added.  A pair of con rods with the error as bias will sort it, everything else is getting numbered as itís added.
« Last Edit: May 03, 2020, 12:22:22 PM by Joules »
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #21 on: May 17, 2020, 09:15:27 AM »
OK, so a bit of a delay.  I had been struggling holding tolerance with my ER32 collets and the block certainly wasn't sturdy for any substantial milling.   I put an order in for a 5C collet fixture since I have a few collects and the 5C chuck for the lathe, just been using ER32 for so long and generally work stuff just isn't that critical.  This little engine is certainly stretching my abilities, so its all good and will translate to better work when we get out of the current mess.

The crankshaft and crank webs have been giving me problems working them out and how to machine them.  I finally came up with a plan, the CAD model below was early on and the counterweights have been reduced to hopefully match the spider and conrod estimated weights.  As I wasn't happy with the ER32, stuff at this stage took a backseat whilst I finished another project that had been on the back burner.   I got a little portable bandsaw, mainly for picking up stock that was too long for the car or I was offered a chunk if I could cut it off.   My Clarke bandsaw had got too annoying for doing fiddly stuff and thought the portable saw would be good in an upright setting.  The base is left over flooring and the table happened to be a bit of 4mm stainless plate, I probably couldn't have picked a worse material. It was horrendous to drill and cut.  I laser cut 6 card templates getting the holes and slots lined up before coordinate drilling.  I opted for a stiff table over ease of blade replacement, hence the torturous blade path but it does end up getting straddled by the fixings, meaning it won't flex.

After this and coming back to the engine, I made a start on my third spider not happy how the gudgeon pins were going to be fashioned.  I cocked up at this stage and cut the blanks for the crank webs before thinking how I was going to hold them.  I had also machined them to final diameter of 22mm, a size I don't have a 5C collet for, excellent planning.   Put what was left of the 7/8" bar in the collet chuck and face each end (plan B)  I can now machine the crank web details on each end of the bar and have plenty of material to grip.

The 5C fixture really came into it's own here.  As a test I set a zero for doing the spider parts and then all operations based off that zero to see how much error I got on the 5C fixture.  Happily none that was of concern, swapping collets between lathe and mill, and different sizes, very happy with the repeatability of this fixture.  The milling of the counterweight was the part I had my doubts about, especially as I was using an 18mm end mill.   Way bigger than I would normally use (thanks Rob) it munched it's way through the brass on each end.

Pleased with the results so far, new spider parts and crank webs done using the 5C collets, no fiddling getting them square and clocking parts up for runout.  Finally for now, a test fit with the older two spiders to check fit and clearances, progress made still lots more to do on this adhoc build.
« Last Edit: May 17, 2020, 04:05:59 PM by Joules »
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Offline Joules

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Re: What do you do when you're given some 1.25" aluminium Hex bar
« Reply #22 on: May 18, 2020, 05:26:26 PM »
Today was tackle and finish the crank webs.  The first job, laser cut a couple of card templates I can use later to file up to.   I had spotted and put 3mm holes for the spider and crankshaft, the crankshaft bore needed opening out to 4mm, in a blind hole as it was still on the bar.  I used a 2mm carbide boring tool to open out the bore, and my thread measuring wires to set the DRO once I had the bore open enough to fit a wire.

Once the bore on each end was done, the crank webs got parted off each end, time to rough saw the parts then glue in the templates with superglue.  I had intended to use the filing machine to do all the work, but went with finishing the profiles by hand with needle files.  The templates were a great help and removal was done with some Acetone.  I had one small issue during machining the recess using the 18mm end mill, it must have dug in and I ended up with 0.28mm difference in the thin part of the web.   I weighed both when finished and one was 6.1gm, the other 6.28gm.  They are both a little on the heavy side and once I have a 4mm shaft made up, I will give them a clean up skim taking them below the target 22mm diameter.

Another couple of parts added to the parts bin for this build.
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