Tx200 zero transfer port

[wonky donky]

Dave

On one of your plug blanks machine in a 6mm deep TP, drill it 3.6mm, then using a small spot drill machine a taper to a depth of 3.5mm on the breech side then using a countersink knock off the front edge to a depth of 0.5mm....then polish it in with fine emery so smooth and round it in. Next flip the plug over and send the spot drill back in to a depth of 1.5mm so we are left with 1mm at 3.6mm.

get a boot lace and some autosol and gently polish the port to just knock off any edges pulling the bootlace thru the port.

If all the theory we are reading is correct this may end up being the ultimate port, if it is drop it in to be drawn up and get the plugs made.

Im thinking something like a 300s seal that allows the barrel to actually touch the port is the way to go or an O ring much like a posted a pic of earlier.

Also remembering that recess that gained you 20fps+ it may be worth machining the plug to 6.5mm depth for TP but the TP is 6mm with the recess 0.5mm like you did before...

I may sketch this up later

Tony any objections if I use a fine taper reamer & a small radius cutter as opposed to the spot drill & countrsink? email me the drg & I'll knock it out...What are we going to do with the other two plugs guys?...VOTE NOW........LINES CLOSE MONDAY AT MIDNIGHT! Calls cost nothing but some suggestions may be laughed at & ridiculed in public.

Okay I'll go!

[bigtoe01]

Dave I do not feel a taper reamer will be tapered enough, Im thinking something like 5mm down to 3.6mm over 3.5mm length then 1mm at 3.6 opening out for the last 1.5mm, a tapered reamer will just not have enough angle to it unless you have a seriously tapering reamer to hand?

The radius cutter...yep what ever you have to hand.

After you do this one I have another idea on a longer port..so save one back, im thinking of adding in the Bernoulli effect also to see if we can gain some extra air for free...much like filling a 6ft long paper bag with 1 breath however it may need a valve of some kind which I will chat to you about first.

[Rich]

Seven degrees of divergence is about 1mm expansion in a length of 10mm. So if the part of the TP that is to be taper bored is say 3mm diameter and 3mm long then it will need to be opened out to 3.3mm dia at the exit. You're probably right, this is more than a taper reamer would give you.

How about turning a piece of silver steel with the desired taper, file it off to half diameter, harden and temper. Hey presto a D bit in no time.

[wonky donky]

Dave I do not feel a taper reamer will be tapered enough, Im thinking something like 5mm down to 3.6mm over 3.5mm length then 1mm at 3.6 opening out for the last 1.5mm, a tapered reamer will just not have enough angle to it unless you have a seriously tapering reamer to hand?

The radius cutter...yep what ever you have to hand.

After you do this one I have another idea on a longer port..so save one back, im thinking of adding in the Bernoulli effect also to see if we can gain some extra air for free...much like filling a 6ft long paper bag with 1 breath however it may need a valve of some kind which I will chat to you about first.

Oh no! thinking this is going to hurt!

Seven degrees of divergence is about 1mm expansion in a length of 10mm. So if the part of the TP that is to be taper bored is say 3mm diameter and 3mm long then it will need to be opened out to 3.3mm dia at the exit. You're probably right, this is more than a taper reamer would give you.

How about turning a piece of silver steel with the desired taper, file it off to half diameter, harden and temper. Hey presto a D bit in no time.

Can you remember how difficult it was to do a taper? I really had trouble with this! HANGS HIS HEAD, SLOPES HIS SHOULDERS & WALKS TOWARDS THE DOOR SHAKING HIS HEAD MUTTERING WORDS UNREPEATABLE!

Okay gone on then I'll do it!

[Snooper601]

I vote for adding some Zephyr style grooves to the face of the plug, then experimenting with groove shape, v shape, rounded, tapering away from the port etc?

Cheers

John

[Rich]

Making the D bit, for the small amount you need to take off, I'd risk the cardinal sin of filing on the lathe, rather than tipping the top slide over. If you fluff it, have another go.

[Shed tuner]

Yeah, zephyr grooves, but you need a port (i got a few fps extra when I tried this, but not a lot)...

Mote is a 2mm thick 25mm OD washer stuck in the end of the comp tube, with a nicely radiused port, 4mm should be fine. Radius can be quite wide/deep as the port vol is so low.. would only be around 0.5mm of parallel sided port in there (after the entry porting).

[bigtoe01]

quick drawing, no detail on taper as i have no time to measure a spot drill (which i still feel will be best...a small one )

https://dl.dropboxusercontent.com/u/920660/wonky2.png

[Rich]

Ideally the entry should be a radius rather than a chamfer, if you can manage it. Maybe be easier done by hand?

[Shed tuner]

Would the exit side 5mm not be better off staying at or below the calibre ? Otherwise the diverged air is going to hit into the breech face ?

[Snooper601]

Would the exit side 5mm not be better off staying at or below the calibre ? Otherwise the diverged air is going to hit into the breech face ?

Port matching like is done when porting an inlet port on an engine. I managed a very useful gain by removing the square edged step on a Fiat twin cam 2l engine where the inlet port in the head met the inlet manifold, it made enough extra power to increase the top speed on the Autobhan by 25mph and that was nearly 25 years ago.

Cheers

John

[bigtoe01]

Would the exit side 5mm not be better off staying at or below the calibre ? Otherwise the diverged air is going to hit into the breech face ?

the entry is 5mm, the exit will be a lot less...i should have labelled the drawing a little better.

5mm to 3.6mm taper, then 1mm at 3.6mm, then 3.6 to say 4.2 on the exit side

entry side radius cut, polished....im thinking it will work well

[Shed tuner]

Ahh sorry, yeah, makes more sense that way lol... in my mind they always flow R > L
Are you left handed ?

[Artfull-Bodger]

Guys you can use a radiused center bit (as opposed to the 60deg type) for the inlet into the port, they come in many sizes, surely you can find something close to what you want?

[greenwayjames]

I was, probably wrongly, under the impression that de Leval nozzles were only used with steam. When I was in my "chuffa" period we used to use them with steam turbines. We made them using shaped D bit cutters filing ordinary steel which was good enough to work brass once or twice and then polished the nozzle to finish. The method seemed to work well enough.