Triumph 650 Twin Engine

[JR72]

Hi Mike

This is absolutely amazing. can`t wait for the next set of photos.
John

[mikemill]

Mike

I agree, the old adage measure twice cut once applies, I find using the CNC process very reliable when all is square the real problems arise when cutting on the angle, you only need the be 1deg out and where are expecting to break through is not accurate and the longer the hole the greater the inaccuracy, hence the need to prove your set up.

Herein lies the challenge and that’s why we do these things, and of course we are adding to the English language by the number profanities expressed.

Mike

[BlueRock]

Great project Mike. Following with interest.

[mikemill]

Progress on the cylinder head, the valve inserts where pressed in prior to cutting the ports, cutting though into the inserts was a bit tense would they line up?  pleased to say they did. I found a 1/8 in rounded slitting saw someone was selling on ebay which was perfect for cutting the fins. The rocker shaft posts are temporary as they hold the shafts for proving the  rocker positions are correct.

1)   Tapping the ports with a 7/8 in tap
2)   Cuttting the fins
3)   Starting to look like an engine

Mike

[Ye-Ole Steam Dude]

The third photo of the engine on the stand is GREAT. It is a beauty.

Thomas

[fumopuc]

Hi Mike, I am quietly following along. An extraordinary model engine, very well made.

[mikemill]

Thanks for your encouraging comments.
 A couple more additions to the head, inlet manifolds and exhaust pipe retaining nuts.

I have shown a design for a basic carburetor, I don’t have much experience with carburetors would someone care to comment on the design or suggest an alternative design.

Thanks

Mike

[Vixen]

Hi Mike,

Some more good looking parts there.

Bill Conners, one of the original members of the ICEBG, specialised in 1/2 scale replicas of motorcycle engines. He always built exact 1/2 scale replicas of the Amal Monoblock carbs. They always worked perfectly.



Bill's AJS


Mike

[Admiral_dk]

Mike - I almost don't dare say, but though I'm sure your carb design will work nicely, it's some 30-50 years too early for the bike engine you are making ....

Best wishes

Per

[petertha]

This topic came up on another forum I participate in. I will share a plot I created that came from that discussion. My approach was rather simplistic. I gathered as many carb sizes endeavouring to include 'proven running' engines. In other words, however the engine designers came up with their size is fine by me. I assume they fiddled to the point they were satisfied & that's what I used based on plans or references. Ultimately I tried to create a simple correlation of venturi size (carb throat diameter) against displacement just to see if data arranged into a trend.

Even this has cats & dogs umped together so take it FWIW. Least of which are fuel type, rpm range, ignition vs. glow, user specific tuning favoring say nice bench idling maybe at the expense of upper rpm etc. I didn't include stationary & hit & miss engines. You can see it has a bit of model engine bias, Perry RC carbs & a sizing article I found regarding Walbro carbs in approximate model engine sizes. I have a nice collectable book called Aircraft Engine Design by Liston which includes a simplistic sizing formula for FS aircraft engines. Just for fun I plunked in model parameters & it somewhat falls in the range. Again, use with caution.There are some outliers, but I'm just the messenger

http://www.billetboard.com/showthread.php/9036-Carbs-Venturi-Size-and-Formula-For-Proper-Carb
http://www.perrypumps.com/prod01.htm

[Bluechip]

Hi Mike,

Some more good looking parts there.

Bill Conners, one of the original members of the ICEBG, specialised in 1/2 scale replicas of motorcycle engines. He always built exact 1/2 scale replicas of the Amal Monoblock carbs. They always worked perfectly.



Bill's AJS


Mike

Ah! So sweeeeet .... 

Once had a G50 engine, would have been a really powerful job had I ever got it going. Compression all the way round ... 
Got it for £50, hung onto it for 3 years, did nothing, sold for £300. One of the very few things I made a profit on.   

Not to nit-pick any more than is necessary, that's no Monobloc. ( If that's what you're suggesting  )

I suspect it may be an RN ?

Can't see the air slot for the choke? The choke slide is on the RH side looking down the carb. on GPs & RNs   IIRC.
Dunno if they were all like that.

Dave

[Vixen]

Not to nit-pick any more than is necessary, that's no Monobloc. ( If that's what you're suggesting  )
I suspect it may be an RN ?
Can't see the air slot for the choke? The choke slide is on the RH side looking down the carb. on GPs & RNs   IIRC.
Dunno if they were all like that.

Dave

Hi Dave,

Ha, ha, I just know there would be some 'rivet counters' out there. 

The point is that Bill Conners built 1/2 scale copies of the full size carburetors and they worked very well. There is no need to try and design one from scratch and then try to get it to work correctly.

MIke

[Bluechip]

[

Hi Dave,

Ha, ha, I just know there would be some 'rivet counters' out there. 

The point is that Bill Conners built 1/2 scale copies of the full size carburetors and they worked very well. There is no need to try and design one from scratch and then try to get it to work correctly.

MIke

Hi Mike

I wasn't sure whether you were referring to AMAL carbs. in general or that one in particular ... 

However, not being one to pass up an opportunity to practise the noble art of being an objectionable bu99er I decided to poke my nose in  ... 

That aside it really is a superb model ..     Would it be that I could aspire etc. etc.

Dave

[Jo]

Ha, ha, I just know there would be some 'rivet counters' out there. 

Looks like a 10TT9 to me 

Jo

[Bluechip]

Could well be a 10TT9 but I don't see the choke air slot. Not sure about that hex head thing either.

Maybe Mike will have another picture. 

See if I can find a pic. somewhere ....

Dave

Piccy found. Looks like there were RH & LH versions .... never knew that, makes sense though.

And:  http://amalcarb.co.uk/carbspec/carburettor/spares/id/4494/