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Posted: Fri Apr 05, 2013 11:12 am
by tonyh
Sorry Nev and Brett. I think I didn't explain myself well.
The advance curve is a gradual advance from tickover to about 3K rpm so it takes into account of the engine speed and retards and advances with rpm like the springs in a mechanical ad/retard unit, but unlike springs which get weak with usage, the new BT-H will remain constant with no wearing parts.

I did tests on some std ad/retard units and some springs were so weak after time full advance was at just over tickover 1200 revs or so.
We have many classic trials bikes fitted with the mags and this is where the ad/retard curve shine through.

All my bikes are old and use my mags (except my 30 year old BM boxer) singles, twins and my V twins. All start instantly and perform well through the range.
Most of the mags I sold went onto road bikes, some on record breakers like 1600cc mega tuned twin spark Vincents with no problems so theres plenty of power available to power most engines from Manxes to VB Ariels and they all are improved over the original magneto. So although I am not installing to much "excitement" in you Brett they do what it says on the tin and offers an alternative to other units which are on the market.

I do agree guys, they are expensive and as a customer I would have to think long and hard at a purchase. I believe Peter has just put the up a little. The first price rise in almost 10 years. However as I used to say to folks. There are other products on the market which you will get the same end result BUT you will need power to run them unlike the new BT-H so suggested they buy something else if there funds do not extend to a new BT-H. I was never into the hard sell, I just told people what I did and what it costs and if I thought I could help them with there original unit I would and save them money. At the end of the day I just love my old bikes and want others to enjoy them without to much hassle.

To your original questions Brett.
I think somebody told me some time ago the original BT-H TT mags had balanced armatures and higher spec windings and condensers. I suppose this sounds logical.

The output, as I said before, is simalar on the new units to the old, but unlike the old units the new ones should not detiorate

The curve I use suits most old bikes. I do have two different cdi units so there is some adjustment but after thousands of miles of testing and experiments on so many engines with different state of tuning led us to what we have.

As for tricks, We have done quite a lot of dyno work and one well known dyno guy asked why we run such large plug gaps, at the time about 35 thou, although with surface discharge plugs this went to almost 100 thou.

He said he never ran any more than about .007 - .010" and as long as the engine is in good fettle he has had no problem with plug oiling or loss of torque or BHP.
It also uses less voltage to jump the gap so win win. Since then I just recommended .018" plug gap which is std magneto.

Hope this answers your original question Brett. I don't want to fall out with people or argue and as the company does not belong to me any more I have no say in the running. Peter the new owner is a good guy and I feel it is in good hands.
Keep your knees in the breeze Tony

Posted: Fri Apr 05, 2013 2:29 pm
by brett.hayhurst
Thanks for the extra info Tony. The website does not explain much technical info that some of us like to know and it is interesting to know how you developed the units.
There is no argument or falling out here, just sharing information that will probably ally fears that some might have in shelling out the coin who have been sitting on the fence.
Regarding my original question, the balanced armatures, better windings and condensers does sound logical as you say, hopefully somebody with experience in the original BTH will confirm but you cant have something spinning that many RPMs having a wobbly for hours at peak load for reliability that's for sure.
Any other development experiences you can share in producing the unit would be welcome also if allowed.
Do not worry about not exciting me, have not met a man that has !
All the best to you

Posted: Sat Apr 06, 2013 9:00 am
by tonyh
One thing I didn't like about the original units were the bearings which had to have paper behind them so the didn't short out, not a problem with the new unit.

I used good quality sealed ball bearings which were good for about 40k rpm. On the magdyno replica they run in steel housings to. The main shaft is stainless steel and the timing is very simple with just a 6mm peg inserted through the shaft to lock the mag in a full advanced position.
There are instructions on the BT-H site if you want to see a little more. The flange twins have 3 bearings.

My test rig went up to about 13000 rpm and they were ok at this rpm so running at the half engine speed most old bikes run they should have a long and happy life.

The mags get hot, like on my old 650SS Norton sitting behind the barrels on a hot day, when you spit on the mag and it sizzles, (this being very unhealthy for the original unit) the only thing I found was the new ones sparked even lower then the 60 ish RPM when cold.

By for now Tony

Re: Difference between TT BTH and regular BTH Magneto

Posted: Mon Sep 17, 2018 1:29 pm
by John Todd
My understanding is that the difference between a Std BTH maggy and a TT BTH maggy as explained to me by a man in the industry many years ago , can't remember who and I've had a sleep since then , is that the TT version used higher strength magnets and had more turns in the armature and hence produced a much better spark. At a higher cost of course. Regards John Todd.

Re: Difference between TT BTH and regular BTH Magneto

Posted: Mon Oct 22, 2018 9:31 am
by tonyh
Hi Brett
I sold the business in 2011 to Peter who calls it BTH Components now. At that time I retired and although I did some design work the year after I no longer have any input in what is now Peters business. So I don't know if he is developing anything down that road. I would have certainly explored several channels but as I said have no connection with it now.
Cheers Tony

Re: Difference between TT BTH and regular BTH Magneto

Posted: Mon Oct 22, 2018 11:36 am
by Richard Kal
In 2010 I bought a BTH magneto for a Super Rocket project.
Expensive, but very happy with it, and would do it again.
This bike is a pleasure to ride; easy starter, lots of power and smooth. Also the most responsive - standard Monobloc used.

The smoothest of five A10's in the shed, and second quickest.
It is also the only one with a belt drive (I used a PE400 clutch), so clearly the belt drive contributes to the feel of the engine.

Excellent magneto; well done Tony!