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paris

Sun Sept 07 2014, 07:26AM

Registered Member #3042 Joined: Wed Jul 28 2010, 12:36AM
Location:
Posts: 121

no taper, no key , no nuts, no thread ...no weld!

this is the article , Im reading the mag

Ash Small

Sun Sept 07 2014, 10:45AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

paris wrote ...

no taper, no key , no nuts, no thread ...no weld!

this is the article , Im reading the mag

Interesting. A one piece crank won't be possible due to the four main bearings and needle roller big ends.

It does seem that 'modern day' thinking prefers Phil Irving's 76 degree crank. There are several threads on this subject on Brit Bike Forum. I think I posted some links earlier in the thread.

EDIT: I found this formula for calculating the optimum offset for parallel twins:

Balance angle = 90 degrees minus the
maximum thrust angle. Maximum thrust
angle: arc tangent, also known as tangent
^-1 of (1/(2*rod length)/(stroke length))
To do this on a scientific calculator:
1. rod length [enter]
2. times 2 [enter]
3. divide by stroke length [enter]
4. invert (1 / X)
5. click [Inv] box, then [TAN]
6. subtract 90
7. result is offset angle
(information provided by Jeff Diamond)

For a 650 triumph it's 72 degrees. This is where when one piston is stationary, the other is at maximum speed.

Lots more info here:

Sulaiman

Sat Oct 04 2014, 10:50AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Just to show the larger ferrite core that I mentioned above, 2861010002;
this core can handle 50 Vrms/turn at 1 MHz and 500 Vrms/turn at 10 MHz,
less at higher frequencies.

1412419786 162 FT153912 Txrxii Pa Mfr185 Board Ii

Ash Small

Sat Oct 04 2014, 12:36PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Sulaiman wrote ...

Just to show the larger ferrite core that I mentioned above, 2861010002;
this core can handle 50 Vrms/turn at 1 MHz and 500 Vrms/turn at 10 MHz,
less at higher frequencies.

My current plan (which isn't finalised) is based on using ~ten turns of copper cored ignition lead (~8-10mm diameter) passing through ~5 toroidal cores, with solid aluminium single turn primaries (wound separately on each core). I'm aiming for 1000V per turn per core on the secondary in flyback mode. 5 cores x ten turns gives 50kV (that's the theory), so I'll need toroidal cores in order to fit the windings into the winding window.

The solid aluminium primaries should aid cooling. I think I need to stick with toroidal cores in order to stand any chance of success as far as insulation is concerned. Insulation will be the main issue at these frequencies.

The pulse generator linked to above used 1000V per turn on exotic solid metal cores in push-pull mode, so I guess I'll need powdered iron cores in flyback mode, rather than ferrite to achieve the VPT required, along with the distributed gap required for flyback operation..

Sulaiman

Sat Oct 04 2014, 02:44PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Yes, winding a well insulated many-turn secondary in the core(s) I showed would be challenging !

I don't think that the peak voltage in a flyback is proportional to core size/type
it's basically set by two things;
1) Insulation breakdown ... primary, secondary and switch (due to turns ratio)
2) 0.5 x L x Ip^2 > 0.5 x C x Vs^2,
energy stored in the magnetic field goes (mostly) to secondary capacitance.

Ash Small

Sun Oct 05 2014, 12:01PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Sulaiman wrote ...

Yes, winding a well insulated many-turn secondary in the core(s) I showed would be challenging !

I don't think that the peak voltage in a flyback is proportional to core size/type
it's basically set by two things;
1) Insulation breakdown ... primary, secondary and switch (due to turns ratio)
2) 0.5 x L x Ip^2 > 0.5 x C x Vs^2,
energy stored in the magnetic field goes (mostly) to secondary capacitance.

Thanks for that furmula, Sulaiman. I'll look into it in greater detail later.

Yes, I've realised that the 'reflected voltage', due to turns ratio will be 'seen' by the switches, this is why I need switches rated for 1kV, at least, with a 50:1 turns ratio if I want 50kV max.

Breakdown voltage should be lower than this figure, even in the most demanding of cumbustion chamber conditions. I realise I need to do some experimenting, but I'm not planning on buying any MOSFETs this side of Xmas, at least, not at the moment.

Ash Small

Thu Apr 16 2015, 11:13PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Just for Paris, and anyone else who is interested, Pendine Speed Week is on this year again, from 23rd to 25th May (bit of a short 'week', but anyway...).

Just got my copy of the 'Rulebook', although my bike won't be ready for this year's event, but it gives me a pretty good idea of what's required if I want to enter it in the future. I do need to contact the Pendine Land Speed Racing Club for clarification on a few points, but I now know what questions I need to ask

I have made a bit more progress, but before I order some Borrani rims from Italy, I do need to check what rating tyres I need. It depends on the 'class record' for 'my class', I'm not expecting to hit over 150MPH over a mile, but the class record may require tyres rated for 200MPH, for example

(I think I'll be in the 1350cc 'special construction' 'A' class)

Any more guesses, Paris?

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