A New 5cc Aero Diesel Engine Project

[b.lindsey]

Ramon, not only are the parts beautiful, but that is one superb finish on the also!!  Still enjoying your build very much.

Bill

[Ramon Wilson]

Hi Guys, Thanks once again for all your kind comments, all very much appreciated.

I have noticed that when making these small engines you never make one but more than one.  In this case you are making 4.  Do you do this just in case one is scrapped then you do not have to start again from scratch?

Vince

Vince - you are correct in assuming that. When I first set out making an engine (the Nova 1) I made just the one and as the case began to have more and more work put in all the old feelings from work leapt to the surface - the more you get done the more there is to lose if you make a boo boo (polite phraseology for something quite dissimilar  ) When the next project was tackled I decided to make two cases for the very reason you state and though I did make a mistake it was recoverable and I ended up with two useable cases and so two engines. So far, on three further builds including this one, that's been the result too 

Regarding the finish Bill and Paul, I think I should point out this is not an attempt to make them 'shiny' but more to eliminate any tool marks as bead blasting will not cover up any defects. With regard to how they will look like these are the case parts for the Mk1 and 2 Eta's after blasting...


and to give some idea what hopefully these will look like these are the Mk1 (left) and 2 as finished


The Mk 3 will be a similar blue head to the Mk 2 (there is little difference 2 to 3 save the crankcase exhaust bosses and the circular top to take the sliencer),  the Elites with gold heads and prop drivers and the Elite Mk2 plain aluminium. (Well that's the plan  )

My experience with aero engines is that their life expectancy is approximatley one flight and then I am picking up the pieces , so best start prepared with a couple of spares 
Jo

If you are picking up pieces of engines after one flight Jo then I think you might have got something a bit wrong  for after a near lifetime of messing with these little wonders of engineering I can only remember one severely damaged engine - I managed to push the crankshaft through the backplate

For those who may be interested amazingly even this one survived unscathed from a near vertical impact on tarmac though going by the impacted spinner material in the hollow prop nut the spinner acted like a crumple zone. (It ripped the engine right out of the airframe though - it lies top right - and one of the prop blades flew past my head some 62 feet away where I was standing in numb disbelief)


Typically this was in competition and was a particularly well flying airframe. It's replacement simply wasn't in the same ballpark so this was a bitter loss and a big setback. There should be a smiley for gutted! The crash was caused by control failure - I had been given some 'genuine duralumin' which turned out not to be so. The bellcrank pivot hole had opened up to such an extent the bellcrank slipped the bolthead .

The engines being built are not intended for an airframe though I have thought about scaling up the respective style of model for this extra Elite - thinking about it and doing it of course being two totally different game plans

Hope this little diversion is of interest to someone

Regards - Ramon

[tel]

OOPS! That'll take more than a lick of paint!

[Ramon Wilson]

Like I said somewhere previously Tel - 'You're a man of few words but much wisdom'    - You've certainly nailed this one

Ramon

[steamer]

Oh Man Ramon....that looks like it hurt bad! .....The engines are beautiful though!

Dave

[b.lindsey]

"If you are picking up pieces of engines after one flight Jo then I think you might have got something a bit wrong"

Or as the saying goes..."if at first you don't succeed, skydiving may not be for you!!"

Bill

[Jo]

 I only did it once, I blame a poor instructor. 

Jo

[Tennessee Whiskey]

Jo,flying models or skydiving?

Eric

[Jo]

I got put off sky diving/parachuting when a lass went through a set of helicopter blades where I was considering having my first jump. 

And as for my instructor for flying model planes I was jumping to assumptions because having only flown once I got introuble for smashing up the plane. Mind you he never used to come home until he had also smashed up one 

Jo

[petertha]

Beautiful work Ramon. For smallish diameter cutters such as these, do you prefer a certain type of tool steel (meaning Oil vs Water vs Air hardening)?

> First up then was to turn some 6mm silver steel to 5mm diameter for clearance and put on the relevant taper - 18 and 25 degrees...

[Ramon Wilson]

Hi Peter,
I usually use nothing more than silver steel or gauge plate (GFS) and always quench in oil despite the recommendation that silver steel is quenched in water. This comes from a work background heat treating and precison grinding many small parts on a weekly basis. It was found that when some of the Sil St parts were quenched in water there was occasionally a degree of brittleness in the parts that was inconsistent and difficult to pin down. Quenching in oil cured that problem without loss of hardness so have done that ever since.

Apart from this oil quench on SS, heat treatment was carried out to manufacturers specifications in proper heat treat ovens - Wild Barfield - and the one thing that was immediately apparent when these were used for the first time at the correct temperature (850F for GFS if I remember right) was the distinct lack of 'redness' as the parts were removed compared to what parts were usually taken too previously when flame hardening by hand. Since then I'm always careful not to overheat the material - just a nice bright red is quite adequate to get the hardness for small tools such as described without brittleness  bearing in mind I very rarely temper them.  My main reasoning about not tempering is that they are very unlikely to be used over the long term and the extra hardness is a trade off to potential brittleness. So far - whilst tempered cutters have failed mainly by wearing - I have experienced very few cutters breaking in use.

That said these cutters - made for cutting the Bentley cylinder heads fins were a bit of a mixed bag but there was a lot of cutting to do. I made the three on the left (all identical) first. The first cutter went competely on the first fin slot  , the second did about one head if I remember rightly but the third did all the remaining heads losing first one tooth then the second then merrily flycutting it's way before finally going with half a head to go. The fourth cutter was made to finish that head off ....


....and the last cutter being longer to get to the central fins slots


One thing noticed very quickly was that as I don't have coolant set up on the mill brushing coolant on in the usual fashion soon led to the cutters clogging quickly leading to tooth breakage - that third cutter was used dry and certainly carried out most of the work. (material was En1a BTW)

Hope that helps and is of use.

Regards - Ramon

[Dave Otto]

Beautiful work Ramon,

The group shot of the crankcase parts is just wonderful; I also appreciate you taking the time to show your cutter making. It is a skill that I hope to improve on in the future.

When doing the backing off of the cutter teeth how much of the original profile is left? On the one or two that I have done it has just been by eye; and I left maybe .02" or so.
Also do you stone the face of the cutting edge or what is left after the relieving the teeth?

Thanks for taking the time (and pictures) so keep us up to date.

Dave

[Ramon Wilson]

Hi Don, thanks for your kind comments - much appreciated.

Personally, I find taking the time to post something is well worth the effort if someone gets something from it even if it's only a minor thing - the nice thing is that it can be done on a daily basis

Re the backing off - having inked up the still unhardened blank I usually file into (toward) and over the cutting edge trying to leave just a witness of ink on the line of the cutting edge. This way any burrs are behind the cutting edge. Care needs to be taken not to hit the next edge in line. Depending on the cutter however sometimes the backing off has to be done with a hand power tool and a rotary burr or grinding tip.

Once hardened I touch up the edges with a diamond file as shown only stoning the faces after if the very edge appears rough. As at this point everything is so close to the original blank it's very easy to overdo it and lose the profile if it's a shaped one so I like to keep this to a minimum. If the cutter rubs (insufficient backing off) or doesn't cut at all then this concern tends to go out of the window as more is ground away.

These three cutters were made for the Racer liner ports. One of the liners was made from cast iron the other a from very tough high tensile steel The first two were tempered and just wore on the HT steel without really doing any cutting - caused more by the lack of backing off than the tempering. The third having been heat treated but not tempered was backed off by hand on the off hand grinder and simply sailed through.


I've made a fair number of cutters over the years but still find I'm learning something near every time I make one but the process is easy enough - it's certainly not a difficult one to accomplish with a bit of care so I hope this discussion will encourage others to have a try.

Regards - Ramon

[petertha]

I've made a fair number of cutters over the years but still find I'm learning something near every time I make one

And I keep learning every time you post a new picture!

For the last set of 'saw blade' looking cutters you posted, it looks like they are kind of modular & attached to a standard tool holder stub (as opposed to the all-in-one style machined from a solid blank). How do you attach & fix these cutters on the shank stub? I see the main hole but no other keyway type slot or pin hole. About what diameter are those? And looks like you have machined in some relief so the teeth stand proud to the main disc body?

[Ramon Wilson]

Hi 'Peter',

Yes these cutters are held on a mandrel using a 2 BA or similar sized metric cap head bolt. There is no keying just the torque of the bolt resisting the cutting forces which so far has proved more than sufficient for the task in hand. Keying or pinning is not a good idea for this type of cutter or indeed thin slitting saws particularly if power feed is being used (I don't have that facility) - as if the cutter jams it usually means a shattered cutter whereas these can at least slip - even so, still doesn't give you much time to stop the power feed if it does though 



You are right in that these cutters were dished out to the periphery in an attempt to provide a degree of backing off without the need to carry that out as a secondary op. The cutters, which are 22mm diameter, are only 2.5mm thick so the amount of dishing (both sides) was minimal in order to keep some strength in the blank. The image shows them before use but as already said they rubbed like hell and soon degraded - lesson soon learnt there then  .

Providing there is sufficient room for an adequate caphead to hold it tight enough I now prefer to make small removable cutters such as these and those made for recent builds rather than machine them from one piece. This one is held with a 4mm bolt. The block in the background BTW has the 'test' cut in it



Hope that adds a little more for you and anyone else interested Peter

Regards - Ramon

PS Should be back on the build by the weekend