foster461 Posted July 12, 2017 Report Share Posted July 12, 2017 Peter, one topic of interest to me is manifold balance tubes. You mentioned it in your SU talk and I can see why the balance tube makes sense with an SU or Stromberg type carb. I wonder what you think of balance tubes in Weber DCOE manifolds where the DCOE is very much dependent on the vacuum signal. I have been following the Yahoo group for DCOE's and these guys hate the Canon manifold with the balance tube despite the fact that many TR6's have that manifold. Stan Quote Link to post Share on other sites
Peter Cobbold Posted July 12, 2017 Author Report Share Posted July 12, 2017 (edited) Stan, The air particle velocity past the jet in Webers nested venturis is much faster than in SUs even at low rpm. It can reach Mach 0.8. An SU at high rpm might reach the Weber velocity at low rpm. So the effect of pulsing on mixture from the Weber jet may be rather limited compared with the SU. The mixture spread at wider butterfly openings may be less in the webers, and a balance pipe would reduce it even more. However as the weber main jet ceases to flow fuel at part-open throttle a comparison based solely upon mixture spread may not be useful. Balance pipes prevent the use of extra long induction pipes for resonance tuning. So high rpm circuit racers may object to the bp. But a road car would need 60cm long intakes to get resonance tuning optimal at 3000rpm and I cant see them objecting to a balance pipe. The firing order 153624 can makes the central SU of a triple set-up run rich. 241536 362415 536241 so a balance pipe can possibly help there. With webers a bp might add pulses too close together for 1 and 2, and 5 and 6, richening the mixture for the second cylinder (ie 1 and 6). If the fuel is accelerated upwards by the first pulse maybe it is still moving when the second pulse gives it an extra shove. So keeping the six entirely spearate might give better mixure control. In short, Stan, Webers are so b888y complicated I dont really know. I tried to find what depression the gubbins permanently blocking air flow in the Weber choke tube causes compared with SU's 0.25psi. I failed to find the information. Probably its somethig they dont want to advertise ! Peter Edited July 12, 2017 by Peter Cobbold Quote Link to post Share on other sites
Alec Pringle Posted July 12, 2017 Report Share Posted July 12, 2017 " @ Roger Some sensible suggestions.......Maybe you should be on the committee! " Yes indeed, Roger makes some good points, although as he (like yours truly) wasn't at this year's event then the comments are to some extent historical. The membership have in recent years twice voted Roger on to the board of directors, but in both instances he chose to resign his position as director in remarkably short order. It would hardly be reasonable to ask the members to elect for a third time someone who has twice found himself unable to work with his fellow directors to the extent that he resigned . . . . . I should add here that I have considerable sympathy for Roger - a director's task was ever onerous and thankless, the more so when one is endeavouring to present a minority viewpoint. Cheers, Alec Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 12, 2017 Report Share Posted July 12, 2017 Stan, The air particle velocity past the jet in Webers nested venturis is much faster than in SUs even at low rpm. It can reach Mach 0.8. An SU at high rpm might reach the Weber velocity at low rpm. So the effect of pulsing on mixture from the Weber jet may be rather limited compared with the SU. The mixture spread at wider butterfly openings may be less in the webers, and a balance pipe would reduce it even more. However as the weber main jet ceases to flow fuel at part-open throttle a comparison based solely upon mixture spread may not be useful. Balance pipes prevent the use of extra long induction pipes for resonance tuning. So high rpm circuit racers may object to the bp. But a road car would need 60cm long intakes to get resonance tuning optimal at 3000rpm and I cant see them objecting to a balance pipe. The firing order 153624 can makes the central SU of a triple set-up run rich. 241536 362415 536241 so a balance pipe can possibly help there. With webers a bp might add pulses too close together for 1 and 2, and 5 and 6, richening the mixture for the second cylinder (ie 1 and 6). If the fuel is accelerated upwards by the first pulse maybe it is still moving when the second pulse gives it an extra shove. So keeping the six entirely spearate might give better mixure control. In short, Stan, Webers are so b888y complicated I dont really know. I tried to find what depression the gubbins permanently blocking air flow in the Weber choke tube causes compared with SU's 0.25psi. I failed to find the information. Probably its somethig they dont want to advertise ! Peter Thank you Peter for an excellent article, most of which I am happy to say I understood. The old adage about carbs too big use stronger springs is born out in your article. Sorry to say I failed to attend the talk on Saturday, pleased it went well, barring those noisy car types outside..... Peter W Quote Link to post Share on other sites
ed_h Posted July 12, 2017 Report Share Posted July 12, 2017 Peter-- It seems a shame about the apparent problems with the live presentation, but from my quiet, comfortable seat in front of my computer, I found the slide show immensely interesting and useful. I never properly understood the full function of the balance pipe before. I enjoy all of your technical topics. Ed Quote Link to post Share on other sites
RogerH Posted July 12, 2017 Report Share Posted July 12, 2017 (edited) " @ Roger Some sensible suggestions.......Maybe you should be on the committee! " Yes indeed, Roger makes some good points, although as he (like yours truly) wasn't at this year's event then the comments are to some extent historical. The membership have in recent years twice voted Roger on to the board of directors, but in both instances he chose to resign his position as director in remarkably short order. It would hardly be reasonable to ask the members to elect for a third time someone who has twice found himself unable to work with his fellow directors to the extent that he resigned . . . . . I should add here that I have considerable sympathy for Roger - a director's task was ever onerous and thankless, the more so when one is endeavouring to present a minority viewpoint. Cheers, Alec Hi Alec, I have only ever resigned my post once and that was November 28th 2016. Previously October 2015) I put my name forward (as an existing committee member) but stood down before voting took place. On the 2015 occasion I was dismayed at the shear incompetence of some of the candidates. Last November I happily took up my position (mainly supporting the chairman Paul Hogan) but it became very clear that all the members of the committee had an agenda that I could not tolerate. What was I to do. It is not always a wise idea to open old wounds as there are serious issues around why I stood down. Roger Edited July 12, 2017 by RogerH Quote Link to post Share on other sites
Peter Cobbold Posted July 12, 2017 Author Report Share Posted July 12, 2017 Thank you Peter for an excellent article, most of which I am happy to say I understood. The old adage about carbs too big use stronger springs is born out in your article. Sorry to say I failed to attend the talk on Saturday, pleased it went well, barring those noisy car types outside..... Peter W Peter, Sorry I missed meeting you. The talk was pretty much an inaudible disaster, so I'm glad the pdf is intelligible. Cheers, Peter Quote Link to post Share on other sites
Peter Cobbold Posted July 12, 2017 Author Report Share Posted July 12, 2017 (edited) Peter-- It seems a shame about the apparent problems with the live presentation, but from my quiet, comfortable seat in front of my computer, I found the slide show immensely interesting and useful. I never properly understood the full function of the balance pipe before. I enjoy all of your technical topics. Ed Thank you Ed. In many ways I prefer quiet cogitation to live presentations. If it were not for the balance pipe function being described in Knight's 1960 article I think the function of the bp might have sunk without trace. I'm hoping the talk will stimulate interest in measuring how big the 'mixture spread' of AFRs actually is. Knight gives no clue. The SU factory records have been lost, so we dont know how the balance pipe was designed. Was it Triumph's design, or SU's, or a toing-and-froing between the two, to tune it? Maybe Triumph archivists can throw light on the process... Peter Edited July 12, 2017 by Peter Cobbold Quote Link to post Share on other sites
Alec Pringle Posted July 12, 2017 Report Share Posted July 12, 2017 Hi Roger, apologies for having misunderstood the detail of your past resignations. As for old wounds, I do indeed sympathise . . . . having departed committee a couple of times myself in decades gone by. Of course there are serious issues surrounding voluntary resignations, I know the feeling . . . . and sooner or later those issues tend to resurface and demonstrate that the person/s who stood down had a point after all. Cheers, Alec Quote Link to post Share on other sites
cvtrian Posted July 12, 2017 Report Share Posted July 12, 2017 I know the feeling . . . . and sooner or later those issues tend to resurface and demonstrate that the person/s who stood down had a point after all. Cheers, Alec quite so Alec, well said. I would vote for Roger tomorrow, whatever he stood for, although given his experiences I doubt he would put himself forward for anything in the future. Ian Quote Link to post Share on other sites
ed_h Posted July 12, 2017 Report Share Posted July 12, 2017 My Triumph motorcycle from the same era has a balance tube between its twin carb runners, but it's just a u-shaped piece of 1/4" or 5/16" hose. I'd think that the small size would present high impedance to any flow between the two intakes, but still, the factory thought it worth the trouble to provide. Ed Quote Link to post Share on other sites
Lebro Posted July 13, 2017 Report Share Posted July 13, 2017 Yep, my "Bonnie" has the same. It detached its self from one end once - took a while to find out why it was running so roughly ! Bob. Quote Link to post Share on other sites
roger murray-evans Posted July 15, 2017 Report Share Posted July 15, 2017 I did manage to attend on Saturday, having had an appointment in Bristol, but for 2 hours only unfortunately, so not qualified to comment on the weekend as a whole. What I have noticed, being in a pecunious position, is the £10voucher for Saturday only visitors,having aquired one on departure,is only valid for another 3 weeks! I don't remember seeing that bit advertised anywhere unless someone can point it out to me, and as my membership doesn't come up for renewal for another 11 months highly unlikely to be cashed in! Roger Quote Link to post Share on other sites
Hamish Posted July 15, 2017 Report Share Posted July 15, 2017 (edited) [quote name="roger murray-evans" post="538827" timestamp=" What I have noticed, being in a pecunious position, is the £10voucher for Saturday only visitors,having aquired one on departure,is only valid for another 3 weeks! I don't remember seeing that bit advertised anywhere unless someone can point it out to me, and as my membership doesn't come up for renewal for another 11 months highly unlikely to be cashed in! Roger As I understand it you can renew anytime not just to words the end at "renewal time" and you add 12 months to whatever you have outstanding. I.e. Thus if you do it now You'll be covered for the next 23 months and use the voucher. Best worth checking with the office though. Edited July 15, 2017 by Hamish Quote Link to post Share on other sites
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