Dslam
Sr. Member
Karma: 13
Posts: 457
Wot ho chaps, its bloody Whitworth!!
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« Reply #1830 on: February 17, 2017, 07:01:42 AM » |
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I don't see how wadding outside the tubes will add any restriction? Probably reduce it..
If you reduce the pipe diameter by a third with perf pipe you introduce an interruption to the natural flow of the gasses changing direction and flow rates, in the process reducing the db's coming out of the end of the pipe. Introduce wadding you restrict the pipe fully by a third. The wadding absorbs sound well but gas cannot pass through it without slowing it and the surrounding gasses down dramatically causing back pressure back up the pipe reducing efficiency............ |
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Olds
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« Reply #1831 on: February 17, 2017, 09:11:32 AM » |
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Actually it's worse than that. Flow rate through a pipe is determined by pressure and cross sectional area. Reducing the diameter by a third, reduces the cross section area by more that a half !
eg. 30mm dia = 707mm.sq. 20mm dia = 314mm.sq.
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Getting older but no wiser! Just using bigger hammers.
The answer to most problems, fire and lots of it.
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BikerGran
Hero Member
Karma: 94
Posts: 10604
Gran Turismo
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« Reply #1832 on: February 17, 2017, 10:11:51 AM » |
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But it's all theory and sometimes things don't follow the theory - I reckon Manky's 'suck it and see' idea is the best way to find out what works!
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You don't stop havin fun because you get old - you get old if you stop havin fun!
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kapri
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« Reply #1833 on: February 17, 2017, 01:30:08 PM » |
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the coppersmith
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« Reply #1834 on: February 17, 2017, 01:55:06 PM » |
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what can one say, that is a good video, however, bashing a hammer with a hammer? you would get the sack where I worked if they caught you doing that. Back to the headers, I'm impressed.
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stinkey
Hero Member
Karma: 93
Posts: 2757
I can't stop building stuff ?,but I'm slowing down
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« Reply #1835 on: February 17, 2017, 02:45:50 PM » |
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I so love that video..techies drive me wild with numbers and calculations..build it in ya shed,ride it on the street..and if it makes some noise..people get out your way..nobody asks to see your graph paper when you pull up at a show ?  |
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Backyard hotrodder,learnt by mistake,still learning ?
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Olds
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« Reply #1837 on: February 17, 2017, 06:44:31 PM » |
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Sorry about the numbers bit. Can't forget being a design engineer. Just throw it together, I'm sure it will be fine.   |
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Getting older but no wiser! Just using bigger hammers.
The answer to most problems, fire and lots of it.
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Manky Monkey
Administrator
Hero Member
Karma: 264
Posts: 55102
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« Reply #1838 on: February 17, 2017, 08:41:03 PM » |
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Now you sound like my brother when he gives me that look of silent despair when I hand him some manky bit of metal to rework.  I'll give it a go over the weekend. Got the rear mudguard strut off at the moment & numberplate mount hanging loose, so can't really ride it, but will try & video it with just the baffles in place. I assume there's a DB meter app' I can download to my phone, just to get some idea of what it's like? |
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On the last freedom moped out of Nowhere City.
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stinkey
Hero Member
Karma: 93
Posts: 2757
I can't stop building stuff ?,but I'm slowing down
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« Reply #1839 on: February 17, 2017, 08:44:07 PM » |
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Sorry about the numbers bit. Can't forget being a design engineer. Just throw it together, I'm sure it will be fine. One cannot just throw it together good sir..nowt wrong with a tape measure and spirit level and a big hammer along with some sketches and calculations too |
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Backyard hotrodder,learnt by mistake,still learning ?
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spanners
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« Reply #1840 on: February 17, 2017, 08:51:18 PM » |
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Sorry about the numbers bit. Can't forget being a design engineer. Just throw it together, I'm sure it will be fine. One cannot just throw it together good sir..nowt wrong with a tape measure and spirit level and a big hammer along with some sketches and calculations too dont forget ,,ticky,, tape,, for them ole,s |
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LIVE FAST and DIE YOUNG,, past 50 AND STILL HERE NOW. WAITING. FOR. THE. GRIM. REAPER
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Manky Monkey
Administrator
Hero Member
Karma: 264
Posts: 55102
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« Reply #1841 on: February 21, 2017, 10:27:12 PM » |
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Right. My day off today so I was running about, picking parts up from welders & dropping them off at powder coaters, but got back in time to fire the bike up this afternoon.
If I remember right, when my Pop was tested the decibel meter was placed 500mm from the end of the exhaust & at 45 degrees to it, (whichever side was furthest from the bodywork). I've downloaded a sound meter app' on my phone, so used that. Didn't have a tape measure to hand when I started the bike up, so used one of the baffles as a measuring stick. They're 30" long, so about 700mm.
Couldn't measure it with the throttle open cos I couldn't do that & hold the phone at the same time, but on tickover:
without baffles- 85db.
with baffles- 75db.
So 30" of straight perforated tube, about 3/4 the diameter of the pipe, has knocked 10 decibels off. Not sure if that's enough or not. Couldn't really gauge what it sounded like on open throttle cos when I blipped the throttle with the baffles in, it hesitated & coughed back through the carbs a couple of times. Mr 'Slam, what does that mean? Too rich? How do I adjust that out?
I also need to check whether the alternator's charging now. Mr Olds left his multimeter with me last time he was here, so if you don't mind Dave, I'll use it, but have no idea how to set it up. How do I set this to check the battery's charging & what should it read?
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On the last freedom moped out of Nowhere City.
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Sid_Vicious
Jr. Member
Karma: 8
Posts: 98
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« Reply #1842 on: February 22, 2017, 12:58:03 AM » |
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If not mistaken it's just to turn it on now and holding the leads onto the batteries terminals now red on + and black on earth - if regulator rectifier works it should show about 14-14,5 volts when running and around 12-13,5 on only battery. The multimeter is already set to 20 volt dc as far as I can see in the picture.
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Nothing is impossible, It just take longer time to figure it out
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minimutly
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« Reply #1843 on: February 22, 2017, 01:42:24 AM » |
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when I blipped the throttle with the baffles in, it hesitated & coughed back through the carbs a couple of times. Mr 'Slam, what does that mean? Too rich? How do I adjust that out?
It's weak....
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« Last Edit: February 22, 2017, 03:17:55 PM by Manky Monkey »
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flc
Sr. Member
Karma: 11
Posts: 283
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« Reply #1844 on: February 22, 2017, 07:17:18 AM » |
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I agree , hesitation and poping through carbs Is a sign it's weak, I'd look to increase the pilot jets by around a fifth, try to find what sizes are available and go from there, rolling road/dyno would be best but costly, or colour tune kits work well , or good old trial and error, allens carbs in Nottingham usually have all the bits. I like tuning carbs four cylinder bikes can be a pain ,4x everything can get expensive
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