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Making a Crankcase for a Boddo Mills


Engine Doctor
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Some may remember that I melted a Boddo mills Crankcase recently while attempting to repair a crack that appered while it was in storage. Why this crack appeared I dont  know but it seems to be a common fault . for those that are interested I thought a Blog of the process might be interesting. Ther will be some gaps in putting all of this on the forum as time allows .

Please note this is my first attempt at anything like this so I waited until I had finished it before posting .............just in case . up until now I have only made diesel head conversions and the od bit for engine repairs and re-cons .

Well after a long search and  no cases are available I thought about making one .

The first pic is the melted case. Fortunately the rear of the case and the cylinder mounting were not damaged so I could take measurements .

I bought some 6063 ali barstock , enough for three attempts at making one .

The hardest part was cutting a suitable length off the bar with a hacksaw . It wasn't this hard when I was younger !

The  the second pic is the ali block  with the front of the case turned down.

The  third pic is of the block having  being turned around and  crankshaft test fit in the drilled and reamed ali block. As you can see the crankshaft  looks like its been turned from a piece of Re-Bar found on a building site from the marks around the crank web !

If all the CS engines ere like this I'm glad I never bought any

Bodo case melted.JPG

Capture Case machi8ning.JPG

Capture Bodo case with crank fitted.JPG

Edited by Engine Doctor
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The next stage was to turn the crank case internal space , then cutting the clearnce for the conrod and for cutting thr backplate thread.

The second pic shows the thread cutting bit and the backplate thead being cut. I measured  the thread at 32 tpi from the backplate and ground the boring tool to match the thread form . Once happy with that I test fitted the backplate and was pleasantly suprised to find it fitted perfectly.

Capture machining internal Case.JPG

Capture Cutting back plate thread.JPG

Capture back plate test fit.JPG

Edited by Engine Doctor
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The next stage required some milling. I set up a milling attachment on my old lathe but it really was to cumbersome and time consuming .

As it was Chritmas I convinced myself I really needed a Milling maching . So some bits and pieces were sold off and a MiniMilling machine was ordered .

This is the csae being roughed out . I couldnt find any marking out fluid locally so I used a black marker pen so that the pattern could be scribed onto the work piece .

The second pic shows the bottom of the case being shaped and excess alloy being removed . The series of flats were finally rounded by hand using a dremmel and a sanding drum then some fine grit paper on a board. Later it will be polished on a buffing wheel to remove the marks .

Next I needed an alloy mount , third pic , to re mount the case back in the lathe as by now it was too delicate and its shape was to tricky  to be held in a chuck. The mount seen in pic two was drilled and tapped for m2 cap heads  to match the holes drilled in the lugs of the  Crank casecase. 

Capture Milling the case.JPG

Case shaping 1.JPG

Capture machining mount.JPG

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Here the case has been fitted to the base and refitted in the lathe . The cylinder base mounting holes will be machined .

for some reason I have lost or deleted the cylinder base being machined ! very odd. so pic of test fit of the cylinder. 

Note the top of the casehas been shaped to fit the profile of the cylinder while it was in the lathe . 

Case mount in chuck - Copy.JPG

Capture cylinder mounted.JPG

Capture Cylinder mount 2.JPG

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The last pics here show the polished case . The engine was test run prior to the polishing but left phone indoors so no pics !! 

NB. those of you who play with model diesels will know that you dont trespass indoors while smelling of model diesl fuel as it can be hazardous to you health if SWMBO is in the house ! so the pics were not taken .

 

Later In the week I am going to aanodise the case . Not sure what colour yet , but pics as soon as its out of the anodising bath.

Capture polished case 2.JPG

Capture  polished case 1.JPG

Capture polished case 3.JPG

Edited by Engine Doctor
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Derv really smells and lingers for months...

 

Mtd1000 is Chanel by comparison...

 

Lovely job there ed, still saving for a milling machine and a new shed to put it in.

 

Wish I had a magic wand for xmas, dam car central locking has a mind of its own...beserk...

Edited by Rich Griff
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Hi ED, watching with interest, you are doing a great job on that crankcase making good use of your new milling machine.

 

I hope you are going to get a collet chuck for your mill they as it will hold the cutter much more securely and accurately than a drill chuck?

 

That crankshaft is a shocker...

 

 

 

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Hi ED. Great to hear you now have a collet set. I use an ER 25 metric set and sometimes squeeze them down to Imperial sizes although the only one I have used recently is 6- 7 collet squeezed down to 1/4". I really should get a few Imperial sizes.

I hope your crankcase work out ok.

Quote

 

 

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Thanks Outrunner. It has been assembled and runs ok.

The anodising should just finish it off.  I would like a bright green finish but have had a devil's job trying to find a decent green dye. The parts come out of the dye soak looking brilliant but as soon as they are put into the hot setting bath the yellow part of the dye seems to wash out leaving a faded blue finish. Yellow seems to be the sticking point.  I bought one  green  anodising dye powder that cost big time for a few grams and that is a horrible shade of green. There are some very expensive dyes around but for the small ammount of anodising I do its just not worth the outlay.

I have bought some bright green ink to try as one post I read somewhere said they had good results with it ? I'll try some test pieces first.

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G'day E.D.

 

You did a nice job machining the new crankcase from the solid, did you fit a bush or is the crankshaft running in the alloy?

 

That crankshaft looks a real horror, it appears that CS only machined the running parts (saves money) but with your demonstrated talents I reckon that a new crankshaft would be within your capabilities.

 

Regards - Chris

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Thanks Outrunner. It has been assembled and runs ok.

The anodising should just finish it off.  I would like a bright green finish but have had a devil's job trying to find a decent green dye. The parts come out of the dye soak looking brilliant but as soon as they are put into the hot setting bath the yellow part of the dye seems to wash out leaving a faded blue finish. Yellow seems to be the sticking point.  I bought one  green  anodising dye powder that cost big time for a few grams and that is a horrible shade of green. There are some very expensive dyes around but for the small ammount of anodising I do its just not worth the outlay.

I have bought some bright green ink to try as one post I read somewhere said they had good results with it ? I'll try some test pieces first.

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9 hours ago, Christopher Wolfe said:

G'day E.D.

 

You did a nice job machining the new crankcase from the solid, did you fit a bush or is the crankshaft running in the alloy?

 

That crankshaft looks a real horror, it appears that CS only machined the running parts (saves money) but with your demonstrated talents I reckon that a new crankshaft would be within your capabilities.

 

Regards - Chris

Hi Christopher. No didn't bother bushing as many old diesels cranks run direct in alloy. Can always bush it if needed later but suspect it won't be necessary as it won't get too much running .

Yes the crank is a horror but it works and is hidden from view. Will use it until it fails. As you say CS saved money by doing this. I suspect that this batch of engines commissioned by the late David Boddington were a small batch made very much down to a price both on time and materials. I'd call it a dodgy deal. 

They also made some twin cylinder millish engines. I'd like to take a look inside one of those !

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54 minutes ago, Engine Doctor said:

Thanks Outrunner. It has been assembled and runs ok.

The anodising should just finish it off.  I would like a bright green finish but have had a devil's job trying to find a decent green dye. The parts come out of the dye soak looking brilliant but as soon as they are put into the hot setting bath the yellow part of the dye seems to wash out leaving a faded blue finish. Yellow seems to be the sticking point.  I bought one  green  anodising dye powder that cost big time for a few grams and that is a horrible shade of green. There are some very expensive dyes around but for the small ammount of anodising I do its just not worth the outlay.

I have bought some bright green ink to try as one post I read somewhere said they had good results with it ? I'll try some test pieces first.

Déjà vu !

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  • 2 weeks later...

The Boddo Mills is now finished . F rom pic 1 engine as it was when I bought it Pic from internet . to pic 2  a melted mess after case started to melt at same temp as the LOW temp alloy rods i used to try and repair it . To pic 3 and 4 the finished engine reassembled .

The Green  Anodising is not as bright as I would have liked but its OK The anodising on the spinner nut is horribly and flaky probably due to the rubbish material its made of . So glad I left the cylinder fins and the backplate in natural ali finish .

I'll make a new spinner nut later as it now spoils the apperance .

Capture Mills Boddo.JPG

Bodo case melted.JPG

Capture Finished Boddo 2.JPG

Capture Finished Boddo.JPG

Edited by Engine Doctor
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9 hours ago, Engine Doctor said:

The Boddo Mills is now finished . F rom pic 1 engine as it was when I bought it Pic from internet . to pic 2  a melted mess after case started to melt at same temp as the LOW temp alloy rods i used to try and repair it . To pic 3 and 4 the finished engine reassembled .

What a nice result E.D.

 

As for 'cracked parts', my own example of a Boddo Mills cost me a whole $25 Au because the propeller driver had split on the first attempt mount a propeller.

A chunk of 2024 T4 alloy, a lathe and a knurling tool soon fixed that.

 

I did add a shim steel washer behind the prop driver as it is running as a pusher engine.

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Hi Outrunner. Yes run it before I anodised it as didn't want to waste time. The Boddo's performance will  ever settle world aligh but it runs fine. I also took the opertunity while it was stripped to remove the contra piston as it was far too tight. A quick clean of the cylinder and a bit of 2000 grit wet and dry on the CP got it to a better. 

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