Member postings for geoff walker 1

Thanks Jason, good information.

Just the piston and con rod to make then lapping and fitting, lots to do but I think the finish may well be in sight.

I finished the crankshaft today drilling the hole for the crank pin.

I read your blog build notes first, glad I did, a 5.5 hole is a good press fit for 7/32" silver steel.

Photos show set up for drilling the crank pin hole using toolmakers button

atb geoff

Hi Jason, John and all

More questions if I may.

The piston design has a blind hole for the gudgeon pin. Is there any reason why?

My view, albeit from limited experience, is that if you drill and ream (5mm) right through for the pin you will accurately size the hole for a 5mm silver steel pin. The pin could then have a bronze cap at both ends.

I assume the cap is to protect the liner in the event of the pin sliding laterally in the hole.

Why does the cap have a hole down the centre?

Best to all Geoff

I have to admit to doing my fair share of whinging on these pages about the content of MEW. I'm not a subscriber because there is seldom anything in it that I want to read, so I will scan it in the newsagents and buy if there is an article or two that interests me.

I'm with you, unfortunately they keep sealing it up in a plastic bag which discourages the casual viewer.

Sadly I'm not not hard faced enough to open the bag have a look and then put it back.

geoff

John, Jason,

thanks for your replies, as ever always appreciated.

I think I will buy a 35 mm. silencer from Just engines, they seem like good value.

I don't want to modify the SC box as I may wish to use it again on the SC.

Really enjoying this project, much of the stuff I make requires very little precision.

This engine has been a real challenge. Can't see an a completion soon, sometime in early the new year, hopefully!!!

thanks again geoff w

Hi Jason and all,

Returned to the firefly recently, a photo of some of the parts in the previous post. (posted before I added text, doh!!!)

The silencer in the photo is off an SC engine and has centre fixing hole spacings at 37mm.

The whittaker drawings show 35.5mm. spacing for the silencer bolt holes. I assume this is to accommodate an OS silencer which has hole spacings at 1.38" (35mm.) If so that seems odd, why 35.5 why not 35?

I am tempted to use the SC silencer and adjust the hole spacings in the barrel to suit although this would of course preclude the use of an OS exhaust at a later date.

Justengines online have wide range of silencers at reasonable prices and varying hole spaces including 35 and 37 mm. Has anybody bought a silencer from them?

Reading online there seem to a variety of different silencers. Silent, extra silent? I would be interested in any opinions on silencers particularly ones suitable for the firefly.

Posted the photo again here. I have shortened the barrel and modified the liner to accept a removable aero sleeve. The head has also been modified as can be seen in the photo.

thanks to all geoff

Mark,

Back plates are available for the M type 1" dia bsw x 12 tpi.

The chucks made specifically for the ml7 etc with the integral thread in the body of the chuck will not fit the M type. The ml7 thread is 1 1/8" dia.

You can use any chuck with a removable back plate and then fit one suitable for an M type.

The back plates occasionally come up on ebay, Tony griffiths at Lathes.co.uk supplies them as do ( or have) Rdg in Halifax.

The back plates that fit inner thread of the ML8 woodturning lathe are identical.

geoff

Thank you Jason, superb,

The links are really interesting and I have found a source for 1000g on ebay.

Progress is slow at at the moment, I thought I was well equipped for this project but as I have no dedicated milling facility all that work has to be done off the vertical slide or the cross slide. I seem to making lots of parts to make parts? If that makes sense.

Will post some pics on this thread in due course but for now once again thank you for your reply.

geoff w

Hi All

Firefly is coming on slowly but surely!

Some questions if I may for Jason or anyone who can help.

I have never done any cylindrical lapping, this project will be the first time.

I assume that the lap used and described by Jason in this thread has one slit which is cut right through and all the other slits just deep enough to take a charge of lapping compound. Would that be right?

I was looking at turning the shaft to no.1 morse taper size as I have a morse no. 1 taper reamer I could use for the expanding barrel, turning the O.D. of the barrel about 0.2 under 21mm. How does that sound?

Finally what is the lapping powder 320, 600 and a 1000 and where can I get it, preferably in fairly small quantities?

Thanks for any help you may geoff

Hi John/Chris

I'm sorted now guys, £9.80 including postage from m-machine-metals, thanks John brilliant!!!!

geoff w

Hi All

Just had a quotation of £49.30 for a length of 125mm long x 30 mm dia en8dm.

I need a drink!

Thanks guys, have emailed wrekin steels to see if they have the size I'm looking for.

geoff

Hi All

I am currently making the whittaker firefly and need some en8m for the crankshaft and the bore liner, about 125 long x 30 diameter.

There is lots of of en8 on ebay but no en8m.

Is there any difference between them?

If yes can anyone tell me a supplier of en8m.

thanks geoff

Hi All

Does anyone know or tried to calculate the compression ratio for this engine?

I understand the basics V1 over V2 , V1 the volume of the cylinder above the piston at bdc and V2 the volume above tdc. I would assume that for both V1 and V2 the volume of the bowl shape in the head will be included in the calculation.

If that is so I get the ratio to approx 9 to 1 which seems about right for a glow plug engine from what I have read.

My impression is that the bowl shape needs to be machined accurately to the sizes given to ensure a reasonably good ratio for the engine.

My engine is coming on well, the crankcase is now almost complete

geoff w

Jason, thank you for your reply, informative and appreciated.

I do intend to make a firefly and will make a start with some of the peripheral parts like the carb and needle valve body for which I currently have materials. In the meantime I can research materials for the "big bits".

I recently made a carb for a Jones .605 and although untested it turned out quite well. The Jones was a considered build but I decided against it as I felt I needed a stepping stone. The firefly may well be that stone.

The drawings are no longer available FREE online, now £17.50 from my hobbystore. The links on aw's site draw a blank. I got my copies through a back copy of RCM and E march 2012.

If I may one more question for now. From your experience of making and running a firefly could you say that a marine option is feasible? e.g. marine flywheel and water cooled head. I intend to make an aero version first but a marine option would be of interest. I have a small 3ft. r/c launch currently electric powered, so maybe next year?

cheers geoff

Hi All

This engine looks interesting and a superb set of photos and build details from Jason, well done sir!

I notice that the cylinder head with it's integral cooling fins sits on top of the the cylinder liner.

Hope this is not a dumb question but does that still provide efficient cooling for the engine?

I've seen engines where the head and fins are separate, the fins are lower down and wrapped around the upper half of the liner which to me would seem to give more efficient cooling of the engine. Is this just for larger engines generating more power and heat?

Just curious guys that's all, I quite like this engine, bought the 2012 rcm and e with the free plan so am very tempted to have a go and make one. I'll give it a lot more thought and research before I do!!!

cheers geoff

Da iawn Wales,

I'm english through and through but having been schooled in Wales I consequently have many friends there.

Wales don't reach major finals very often but when they do they certainly make the most of it!!!!

A pre tournament outsider can win it, remember Denmark in '92.

geoff w

Hi Brian,

I have a single drawing from Woking precision models circa late 70's

It is for the potts attachment you see in my picture with this message.

If that's the one you are making send me a P.M. and I'll get it to you.

Actually your name is familiar, did I sell you some potts castings for the pedestal design?

If so you may still have my email address, have a look.

geoff w

So who's the old guy on the cover of MEW 243 ?

Well I believe his name is John Stevenson.

Nothing like Benedict Cumberbatch but does have a passing resemblance to Jim Broadbent (Roy Slater in Only fools and horses)

geoff

No Worries Eug,

We all make mistakes and you are NOT a twit, just remember you have forged your place in the history of dummond lathes with the inspired use of a secondary thrust bearing on the M type spindle.

I have followed your lead on my '29 drummond and '48 myford, just the job Eug makes a real difference.

All the best Geoff w