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 returning to bantam racing

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Derek

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PostSubject: Re: returning to bantam racing   Sun Mar 04, 2012 4:43 am

Hi Mick
here's some background so you or others may be able to point me in the right direction.

The complete box is an original D1 CR - its in prety good condition doubt its been used for racing, I have changed the slider gear your refering to, I know what you mean. "actually never new these gears would go together the layshafts are bigger diameters I tthought, however it is sitting inside a 175 D7 std set of cases!!, surley this should not make any difference.

the problem I am refering to is "the box does rotates by hand, but just very tight, but if I take either of the shafts out they spin, but only when fully assembled although dad hase fitted a new bronze bush setup in this as its a 175 dont believe changing to a roller is really needed at this point, but my godness there is somthing wrong. intend going in the shed this afternoon to have another look.

I was wondering if we had a gear binding or an alignment issue, not come across this one before.

and mick I removed both slider gears and its the same!!!!!!. pointing me to top gear could the layshaft be bent ? checked the mainshaft as we machined it its spot on.

but I tell you what I have notised is the slider on the mainshaft is only 3/4mm on the spline on the mainshaft when in second gear, thought Ishould explain about what we do here, from my notes we would always machine 2mm off the first gear outer it has a 3mm taper anyway that does nothing, the face on the main shaft to drive side bearing, this moves the shaft furthure through the cases and engages more of hobbers) he came up with this ideas while we were checking an issue - Dad use to rebuild all the gear-cutting m/c (Phouters and Gleesons machines at Rolls Royce engines), this was his idea, it quered the splines from wearing tapered on the end that cause jumping out of second gear, but if the slidersare worn, we would check by (as there is a masive difference in machining at BSA on both the mainshaft spline and slider gear) (22 TOOTH) - We always fit them to a shaft that is polished to have a 3 thou taper on its O/D thats fits the internal size of this (mainshaft) slider gear we then go through all our stock of used or secondhand sliders to pick the best item, this is very simple, how far up the taper the gear will go, when you push it on , this is a very suprising test, and very simple to do, and my goodness it will avoid that dreaded issue of jumping out of second, "no mater how good the selector mechanisum is, if this is poor you will have issues. (and the Tom mod is brilliant shame there is not a drawing on the technical page on it)!!

I have not done the "tom mod" to this gear box untill we need to, but we have brased a tube on the lower angled plate to stop it from bending, during the heat of race changes, the selector mechanisum bends by as much as 2/3mm we found this would propogate jumping out of second gear as it too moves the secone betwen a neutral between 2nd aand top.


but I will report on what I find, while trying to resolve this tight gearbox issue, and i will double check what your refering to mick. amazing sometimes it can be looking at you but takes ages to spot it.

unless anyone had a similar issue please report "so I can plumb for that" first.

kind regards Derek
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PostSubject: Re: returning to bantam racing   Sun Mar 04, 2012 6:19 am

ref my gear box found the problem it now spins like a watch, well almost.

I notised the layshaft, has quite a bit of ply however figure as I had to tap it back and forth its an alignment issue, I made a lap using an old gear change shaft removed the shafts locked it back up then lapped both bores at the same time, cleaned perfect now. but I put rolle pins in the bushes to stop them rotating for alignment issues could develop if they rotate.

forgot how many things you have to do when you do a new engine from scratch, and mine is an almost std arrangement.

regards Derek
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PostSubject: Re: returning to bantam racing   Tue Mar 06, 2012 2:34 pm

175 std Crank flywheels - blimey its out of alignment by quite a way, I forgot to fit the side plates so fitted them after, and so had to centre punch to hold it in place, std BSA Practice, I just did not realise this would have consequences, anyway we are going to fit plugs in a hollow pin to tighten it up a bit more, as we did with "Eds short stroke motor".

looks like every one is busy ! again.


Derek
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PostSubject: Re: returning to bantam racing   Thu Mar 08, 2012 7:19 pm

right cranks pin plugs made and fitted but as a result of this I can not get the alignment any better than 0.0015 though on the timing side and 0.0005 on the drive side, These are standard Big flywheels so ! is this acceptable for large flywheels. ? the pin with plugs is now great Mind you Ihad to put 10 and 11 tons on them to get them in I thnk we made them too big!! dad alwaysdrills a small hole in them 1mm and then puts a tiny casnit skin on them so when we wish if need be we can drill one out to access the other for pushing out, the tiny holes also let the air out,!

I actually spent three half hours trying to get it any better to thi, So feel it's about all that can be achieved with this set up, with the crank pin plugs in, we had to really hit it to move it, We found a real easy way of moving them controllably, as we noticed hitting it, (per normal alignment) is not very controlable as to how hard you have to hit it, some times it moves somtimes it does not, and some times it goes the wrong way, so I made two small jacks buy cutting down a short nut and bolt to go between the fly wheels, you undo them to move it (much more controlable) and simple "hey presto when you hit the fly wheels really hard it also controls the direction they move in with the jacks in .

so if someone could advise on the run out figures, please "are these ok for large flywheels". ?

The crank has been bored on the main crank pins holes by dad to a 22mm diameter in his small lathe (just dont now how he does it on such a small lathe he runs with two small weghts as counter balancers!).


regards Derek
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john bass

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PostSubject: Half a thou too much!!   Thu Mar 08, 2012 10:14 pm

Half a thou too much Derek! One thou was always the limit in my engine assembly time!

First time I ever heard someone admit to being over the limit.

Mostly the engine builder proudly shouts out -- "... the shafts were `dialled-up´ and alignment was zero-zero!" Which is highly suspicious ... Even Roy Bacon in his `Two-Stroke Tuning´ does not mention the limit of run-out -- he just says (what we all know), "A well-aligned crankshaft will run smoother, give less vibration, allow the engine to develope more power, and improve reliability, so is vital."

I stripped my new 350 scrambler Bullet engine after it had ruined its plain big-end and maybe the wrecking of the big-end caused the misalignment -- which was 2 thou -- but I think it was probably as it had been ex-RE-Works... Big-End failure was lack of lubrication -- after the oil pump failed.

I always worked to getting the misalignment to under a thou. On my old 1927, 500cc Triumph there were two holes in each of the flywheels and two dowel pins to allow "Perfect" reassembly but keeping the wheels parallel was still difficult and a painstaking job requiring much patience. After fitting a new bearing I used the dowel pins on reassembly and whilst tightening up the nut checked constantly on the flywheels being parallel. It worked. When dialled up the shafts were one thou out of alignment and I left it alone. The most important aspect was to get the Flywheels (whoops! I mentioned them again!!??) parallel !! If they are not it surely shows up on alignment measuring.

All the best in your endeavours!

Cheers!
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PostSubject: Re: returning to bantam racing   Fri Mar 09, 2012 12:00 pm

Hi John.
it was a late night last night,! some one emailed me today, and asked how I was measuring the readings i "total indicator reading" they were TIR but I forgot to halve this figure, to get the runout, so we have slightly better runout and accuracy, than suggested, I have been out again tonight trying to see if I can get it any better, but no way it just will not I recon the BSA machining is out one side to the other,
ok for large (dare I say this) flywheels ?.

regards John.
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PostSubject: Flywheels - 3   Fri Mar 09, 2012 8:52 pm

We could get into flywheels-3 Derek but the rest of the Bantam lads mightn´t go for it!

Don´t forget that both wheels have rotational inertia so keep them light and small -- not forgetting the tyres of course, they ought to be very thin without too much weight!! Have you seen the America military development of a plastic wheel with no tyre.

Cheers!
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PostSubject: Re: returning to bantam racing   Sat Mar 10, 2012 11:58 am

Hi John Ive been trying to rig up a support for the conrod sa that I can hold one side in the lathe the other end with centre to allow me to lightly machine the O/D and sides just to clean it up a little, apparently these were made on a line and located indepedantly to each other, on a transfer machine as were the cases, not sure there was any selection fitting after, so no way would it have been that accurate, just never had the technology they have today for super accurate volume production parts.

Derek
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PostSubject: Sounds dodgy Derek!   Sat Mar 10, 2012 7:36 pm

In the lathe -- sounds dodgy Derek!

I forgot to ask HOW you measured the run-out? The ideal way is on two vee-blocks on a surface plate -- i.e. To have each shaft resting on its own vee-block and rotate very slowly whilst clocking with a dial guage.

Cheers!

JayBee.
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PostSubject: Re: returning to bantam racing   Sat Mar 10, 2012 8:53 pm

yes its taking me some time to sort it but its quite durable and very efferctive run out on the flywheels is 0.000 and sides!

anyway checking in the lathe with a centre in the tail stock and chuck clock on shafts as close to the flywheels as possible will try loading a picture.

why you asking John ! and keep them comming its all on the learning/reminder curve.

regards Derek
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PostSubject: Re: returning to bantam racing   Mon Mar 12, 2012 7:54 am

Hi John you said it sounded very ? to machine to outside of the flywheels in the lathe but actually very easy to do and means the accuracy of the flywheels can be zero zero, i have to say Im happy with it now and the plugs have really tightened the crank up it did not seem to make much difference at first well only a small amout That i could tell however now its a completly different story why do you think this is My dad says the metal moliquel's grow together over time the longer its left the better it will become upto a point obviously it will not keep changing. your the development Engineer so could you explain this (and yes Im taking Flywheels again but on a different note)

compression ratio
is one of the single items I have found you can change and if its not corrct it makes a pronounced effect on both the power out put and the torque - also never new it had such an effect on the lower end of the power band / torque figures on the Dyno.

I have now three heads Ihave been playing with the one I used last cadwell meeting, 14cc the one I took off when it kept overheating that is 11cc and a new one picked up from AUTO JUMBLE FOR 10.12cc measured with burrett ? but its seems even this is hit and miss as do I come up the plug hole/half way or to the btm of it. taking into considereation Con rod /crank strech at Top dead centre do you think this will also have an effect on the comp ratio, as it appears all the books says minimum minimum for squish clearence is bettter as this gas air/fule charge is never used anyway.

anyway another question for TED i purchased a head from Ted at cadwell last year, its combustions is very much smaller than I have ever run, its quite an unusual shape too, anyway what Im asking is Ted what was the squish clearence on this head as I have measured it with Burrent its comes out at 8.9cc with a dummy piston in a bore, how did you get away with such a high compression ration Ted, what fuel were you using and was you using a retard ignition system.


lots of questions here John/Ted ! or please others "feel free to comment" on this.

regards Derek

!
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PostSubject: Hi Derek!   Mon Mar 12, 2012 2:13 pm

Hi Derek!

No! I meant measuring the runout of the shafts on the lathe. I know a lot of people do it but there is only one positive way and that is having each shaft resting on a vee-block on a surface plate using a magnetic base dial guage.

Holding the assembly with shafts between centres is wrong OR holding one shaft in the lathe-chuck and measuring on the outer shaft is also a NO-NO-- both methods lead to inccuracy of measurement. With crankshaft mounted between centres, you need play to rotate the crankshaft and that small amount of clearance gets magnified at the shafts. If you tighten the centres -- by the tailstock -- the whole assembly is strained and you´ll certainly see out-of-alignment.

Sorry if I am late with this -- (or that you have done the measuring by vee-blocks already) -- but I assumed you were familiar with this procedure.

Of course, there are a thousand ways to kill a cat -- as my old boss² at Simms used to say -- and maybe you have another method I know nothing about....

If you had to machine an amount off of the flywheels then surely the shafts are not accurately lined up...??

²... he (my old boss) used to say that. That was when I presented a test programme to him for his approval that he considered was too complicated -- he´d finish by suggesting I was killing the poor cat by dragging it brains out thro´ its backside.

Cheers!
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PostSubject: Derek! Re CR....   Mon Mar 12, 2012 2:48 pm

Hi Derek!

I only got up for a drink and now I´m stuck on here with your compression ratio query. Measuring with a burrette is the normal way and fill the chamber with the oil up to the bottom of the spark plug hole. Then fix the upside-down plug in the vice and pour in -- alongside the centre electrode what it takes, and add that bit to you chamber amount... Making sure of course that the plug is not too long or too short!!!!

The difference of a few thou on bump-clearance doesn´t make much difference -- does it??
The squish at 35 to 40 thou can only change when the piston stretches. Icarus-2 had standard BSA pistons (lots of them) that elongated their small-end eye. It used to go really well just before seizure.

The burrette method of measuring CR is even used in the best of Auto companies.

This following indulgence, I think, proves the point:-

What I bought whilst at Ford Dunton for diesel engines was a sonar device which worked on the Helmholz principal which is much like what happens in resonant exhaust systems.

Measuring procedure was, take out the injector (Ford Dunton, circa 1971 now!) -- pop in the probe and set the thing in action. What it did was to send a sound wave down to the top of the piston and when that reflected its signal was modified to shows CCs of volume on the VDU. Only a couple of the engineers used it. They didn´t trust it. If they did use it they´d double check with the burrette....
Wonderful instrument...!!


I spoke about compression ratio and fuels suited to levels of CR, long ago and was warned not to mention high octane fuels but there is a need to use over 100octane fuel if you increase the CR over say, 8.5:1 (my opinion??) to above 9:1 ...-- some will argue this point and say higher CR on the aeroplane petrol ... The point is that the dynamic CR can be greater than that measured statically if the gas flow and pipe are well tuned and you run into detonation ...

I hope this is of some use. I´m back to my bed....

CheerS!
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PostSubject: Re: returning to bantam racing   Tue Mar 13, 2012 5:12 am

John you need help "I mean come on mate - 3.45 am" at your age you really do need to talk to someone.! lol

On centres V veee blocks - "thanks John" but I know how to measure alignment on a crank, thank you and I don't do it on vee-blocks.

As for you comment about flywheels, "why did you know the BSA machining tolerance on flywheels" or in the machine shop
0.005" yes thou to center tolerance, but I bet none of them are even close to this, The reason Iknow this is "they were m/c on a transfer machine with Bronze bushes for alignment that slid up and down, sdly these were also used to locate the block agnst it

but even worse transfered to 3 jigs on different lathes! for turning, could I suggest some accumilation of tolerances" ! well I will leave you to that - "manufacturing is my field of expertise" and John Im laughing at your last comments. I would stick to your field of expertise, also did you know just before BSA closed its doors, in excess of 500 tons of items were rushed to be finished off, some were used for bikes but many were sold to the sapres people.!

I would suggest as they new they were going to be sold off ? as they believed old man Onslow who had agreed at this time a price to purchase the Bantam toolg name and all that when with it, but he did not want the workforce, ? well the rest is history,
Anyway all these parts found there way into the spars parts aftermarket and new parts build program !! can you imagine anyone loading a component knowing he is out of work in the next few week "properly".???????

leave the rest up to you my learned friend, if I were you I would stick to what you know about" maths on flywheels and flywheels 2" and Im sure many other things to come.!!!

but the ford stuff "jOHN we know you worked at Ford, you keep telling us, But I have to say I never find your posts boring or long just full of great reading.

cr and Holmtzs resonance could this be another interesting subject I have certainly well can not remeber hearing this word.

"john" what is Holmzst.
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PostSubject: Stick to my line of expertise...   Tue Mar 13, 2012 6:14 am

Derek!

You´ve made a lot of assumptions not based on fact -- you do not know my LINES of expertise ....

You´ll find Helmholz Theory by going onto the Google site and as for that matter any other technical questions you might have...
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PostSubject: Re: returning to bantam racing   Tue Mar 13, 2012 8:53 am

Hi John

I'm Just kidding ! Honest" and I have looked at the Holtsmes "very interesting" thsi is really going to help me, but I dont see how it affects resonances "well possibly", seems Holts has quite a famuse family name for brewing light beers what a great subject.

Regards Derek
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PostSubject: phyisics   Tue Mar 13, 2012 7:16 pm

Hi John

The variouse sives are linked to a bulb like sphere


It can be shown[2] that the resonant angular frequency is given by:
(rad/s),
where:
(gamma) is the adiabatic index or ratio of specific heats. This value is usually 1.4 for air and diatomic gases.
A is the cross-sectional area of the neck
is the mass in the neck
P0 is the static pressure in the cavity
V0 is the static volume of the cavity

For cylindrical or rectangular necks, we have
,
where:
L is the length of the neck
is the volume of air in the neck
thus:
By the definition of density: , thus:
where:
fH is the resonant frequency (Hz)

The speed of sound in a gas is given by:
,
thus, the frequency of the resonance is: ?? loads small cals here possible a physasist theorist.

so john what happened to all those designs, to run the internal combustion engine "purchased by the automotive industry powers, specifically water energy or black energy. only read about it.
I think its called Fusion

and I feel your miss reading my post! my friend, you often correct me" I dont generally reply with intent, but I have re read it and can see no issues with it. but I appoligise if this has given you the wrong thoughts on my conclusions, all done in good faith, I mean every word, not as onther has said a "taking the michael ".

very best and kind regards Derek
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PostSubject: Fusion you say Derek...   Tue Mar 13, 2012 7:47 pm

Fusion you say Derek -- more like a Con...

Lots of graduates have written²² engineering & scientific papers on all these scientific laws that were established by very clever blokes yonks ago (mostly with fantastic `von´ and German-Austrian-French sounding names) -- in such a manner as to make the subjects more mysterious than ever. Japanese mostly -- Chinese coming on fast too!!


Return to compression ratio measurement:-
This compression-ratio measuring apparatus I mentioned electronically compares the sound of a hollow tube of the same volume as exists in the combustion chamber. By running thro´ a great number of frequences and accents of the sound coming from the hollow tube and comparing that with what comes out of the combustion chamber (as repeated sound) it matches the two together and then its signal-conditioning equipment gioves a readout of CR...

. Blow across the top of various sized & shaped bottle tops and you get an idea of how the thing works -- the whistle changes: frequency, stress and pitch vary....

The writer of the above paper (1st para...) would then prove by several pages of fascinating mathematics how that happens.

By now -- 43 years later than the one I had -- there must be a proprietary device available on the market at a reasonable price. You could get one, hire it out to club members and get your money back. I´d really like to hear that it was widely accepted....


I think you might be mis-reading my scribbles too. I don´t set out to correct what you´ve said -- I am mostly trying to put forward something to argue about. Centuries old -- accepted -- ideas and procedures have to change when modern equipment and methods arrive, so I´ll go along with any innovations that anyone brings into the scene. It keeps my brain active to prove new things to myself and your trips into calling something OLD HAT & my line of expertise I find amusing although sometimes exasperating which must be as good for my ancient body & soul as a half hour of relaxing massage!!

²²... university graduattes are made to write...

Cheers!
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PostSubject: Re: returning to bantam racing   Tue Mar 13, 2012 10:58 pm

Hi , all ,
Helmholtz resonators , at least when attempting to represent modern 2t engines , seem to offer a solution to resonance problems
but in fact deliver very little of substance and just confuse . Have you ever wondered why , in the early years , engines always
seemed to have long inlet ducts , whereas , today they are universally short ? Look to von Helmholtz !
Just as a simple example , a resonator as originally conceived , didn`t seem to factor in the obvious, that the crankcase is constantly
varying it`s volume and the frequency of the pulses produced, change, and, the flow reversals create waves that happily bounce
back and forth messing every thing up . So it goes on , it is all very interesting but as a design or tuning guide for Bantam engines
i don`t think so !
Pop the concept back in Room 101 , and return to the esoterics , or , the empiricism of proper Bantam technology !


Bye for now , Trevor
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PostSubject: Trevor ...   Wed Mar 14, 2012 3:17 am

Trevor -- tutt-tutt, young man!!!

Where on earth did you get the idea I was suggesting Helmholz theory be applied to Bantam engine tuning???

I was NOT using Helmholz theory of resonators for anything other than that of measuring compression ratio -- please don´t go mixing up my crud with other people´s crap -- I´d just like to know what I had as an experimental apparatus -- 43 years ago -- is now accepted as Norm, or has it been kicked under the carpet forever?

Cheers!

Ah! PS. Anyone know of a good Harp going cheap?

I want to get in some practice just in case a mistake is made and I go up top instead of where I want to go -- down below, where its warm and the some of the naughty maidens are bound to be...JB.
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PostSubject: Re: returning to bantam racing   Wed Mar 14, 2012 5:41 am

Hi John Trevor

Trevor thanks for that snip bit. may be you could coment on what I have going on in my transfers !

John I have to say im releaved we managed to sort that one out!, seems so easy to write one thing but mean another, especially these days Im trying so hard not to creat waves, but to create and develop friends. when I read things there is usually two meaning Itake from it I have noticed this and it is a part of my disability. I have often PM some one horrified after I had re read it. for them to say no problem never read that at all. ! good now back to the seriouse issue of tuning.


Tranfer, I by way of kind direction took a mold of the transfer to my Horror Ifound some shape just can not see looking down at them anyway
used some devcon over painted with araldite to mold a nice curved inner shape trying to copy what i had seen on pitstop .Buz

anyway "my god" what a difference but very short lived its almost as if I can see as though some one after running under load, had mushed somthing back down the transfers and started eating away at this devcon, do you think this could be the wave or the pressure of the cylinder causing reverse flow down the transfers the shape and what it did to the devcon is very interesting, and I think with this pipe I either need a bigger port timing on the exhaust or a longer taper on the front pipe (to creats more suck) or possible a sharper edge on the exhaust port.
also My torque BHP has made quite a big jump from about 7000 to 10,000 ? any ideas or suggestions on what is happening here, the other thing is the temp in the exhaust has dropped too.

however this product used to create curves on the inner transfers on one side actually is almost blocking the port the way it has erroded

any way any comments (other than use a better product for the moldings for the inner transfer wall ducts


regards Derek
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PostSubject: Re: returning to bantam racing   Wed Mar 14, 2012 6:41 am

Derek ,
Look in Phenomena plus , the spike in the Blue transfer trace tells you all you need to know , and , a lot more besides !

Trevor .
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PostSubject: Re: returning to bantam racing   Wed Mar 14, 2012 11:22 pm

Hello Derek, and all ,
Can`t say i`m the least bit supprised you have seen a performance boost by improving transfer flow , they are
after all the most important "ports and ducts" in the whole engine , any flow separation and subsequent colision
between parts of the gas stream cost power . Keep at it and you will realise the full potential of your motor.
Is this a reed or a piston port job ? a If you are burning the filler in the ducts then at transfer opening combustion products are being forced down the
transfers as well as out the exhaust port , all pretty obvious as a diagnosis . Cylinder pressure is still much higher than
the crankcase , this might suggest the cylinder porting spec is short on blowdown time area giving a limited period
for gas evacuation . It might also indicate that crankcase pressure at transfer opening is too low , do you run a long
rod on this engine ? The pipe`s extraction effects only fully come into play around bdc , although there is some effect
earlier in the cycle . No pipe can cover all eventualities , there is always compromise to be made to say nothing of
poor design and construction . High pressure gas will always run to a low pressure area , no way round it !
It is worth mentioning that at either end of the power band on the works Aprillia engine , combustion by-products could be
wiped from the carb bellmouth ! Now that really makes you think !!

See you later in Phenomena plus , Trevor
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Derek

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Number of posts : 1065
Age : 56
Localisation : worcestershire
Registration date : 2007-06-15

PostSubject: Re: returning to bantam racing   Thu Mar 15, 2012 7:58 am

Trevor/John/ al

sorry this is a long one but really found some interesting data here its all getting rather exciting,

Trevor !!!!!!!!!!!!! "blimey" how did you know I was running a long con rod"? it is a 54x 54 short stroke and a piston ported reed valve, with third port at the rear and a small window (that is too high up on the piston rear skirt) helping the cooling, THE Con rod /length is 250cc maico 125mm centers, I need this as the cases are standard, when we built it I was an apprentice, so could not afford to do it the other way, stuwart johnson made the crank £35 quid he charged me, five weeks wages at the time!, yyes appprentices earned £7.0 a week in them days, it should have been a long stroke, but he ran out of time, and sent me a 54mm stroke crank, we never new for 4 years, it was a short stroke anly when some one poited out we were runing 96 thou BTDC ign timing that it would not pull over 8000rpm? never new that much about ports and timings, well dad did, we started playing with lifting the port timing after Tom said at snetterton 1978/9 ish we should be running 96 deg on the exhaust, we broke throug on the casting (Nigel) but my goddness what a difference this made after the repair, it was like riding a scalded cat, as soon as it hit 7000 to 10000, after getting some direction and help with a pipe from the good looking brother!, we actually started to get higher places all History.(yawn yawn)

anyway - my set up is as we run is a std Honda MT mk1111 125 reed Block 82 I think, vintage and my own pipe ala "support from Mesers Amos and Al, sorting the overheating tail pipe and timing issues, and a few of my old notes and ideas from what I have learnt recently.

we new and were expecting to be down on power at the last Cadwel meeting, but what an unsuspected increase in torque. (Transfers is where ist at") I was actually running a 14cc head volume, about 9 to 1. it was all I could get away with untill I found the problem with, first the tail pipe being too small (thanks AL) and a manufacturing defect !!! on my part. Then the inner diameter of the silencer under 22 mm, anyway when all sorted it dropped piston crown temp we think as the exhaust temp down by 270/300 degrees!! is this a lot!

anyway so being down on power was expected, I just wanted to get some finishes and enjoy the weekend, her in doors was attending and I dare not finish a race, even if at the back and there is no shame in this, we all have to start somwhere or restart somewhere!.

anyway to the here and now, I have been able to coax a little more HP out of it, again Trevor is spot on, !! with some more mods to the inner transfer walls, trevor spoke about (anyone reading this should really take notice of this very important, point and re read tervor post on transfer ducts " as we did nothing but reduce the volume and smooth out the duct flow making more or a curve, and it gained 3 HP on a direct comparison before and after,? not just at the top but all the way throug, the range,! "amazing", what you pick up on here, all I need is another ten pointers like this and I will be in the ball park, "extra weight and all". !! mind you the wau om going it to will be moved!

we have nowhere near the quoted 26 or 30HP! respectively, but we are back to producing what we had in 1989/90/91 and a very modest 19.4 BHP on a dyno, or there abouts, when I sold it. We have a completly different Pipe though, and a much better spread of power, I expect to do quite well when learned my racing lines and get the london boys to tell us how to properly set up a snell box!!

better still no need for all that clutch slipping, well possibly some, we also have a lot more "comp ratio" thou as we are now running only 9.65cc/9.68 - so I'm guessing its tollerating this better, because of the bigger tail pipe, maybe it was always too small for the engine in this state of tune.

Trevor the only thing I can not do is lift the barrel by more than a few thou, but this will lift the transfers too, I could paint some araldite in the top edges of the transfers to test this before proper moding to try this. I think this should be durable and 0.010" per coat "would this be enough. or what it have the desired effect, as I run on dykes rings at the top edge of the piston, we are not much above, 0.010" what do you think Trevor is this enough or are you saying I need to lift it independently of the transfers, properly ? .

the reason I can not lift the barrel much (again you picked this up in your comment Trevor) is that the exhaust port uncovers at Btm dead centre connecting the crankcases, not ideal, Ihave tryed to resolve his with too many issues we ideallly need another barrel anyway this will never happen on this engine I will try and find a suitable piston that is pegged properly, and is as a result of the wrong different piston and rings popping into the inlet port.

I''m due on the Dyno again soon, so busy with work, I will be looking and respond taking a sat phone so I can link via my phone through my lap top "Technology is amazing" ! not sure I will make the practice day, I was looking forwards to see what correlation I could see between track and dyno, as Ihave been told to expect none I hope not, as the carb setting have changed unimaginably. just one more point for Trevor, I have three transfers I will try to load a photo, but I have reverted to a much smaller carb and getting much bettter drive /Torque on the lower end, hence no need for the clutch, I was assuming from one of your posts there was no point in a carb bigger well bigger than the transfer port area's added together, if this is the case does this thory mean I could run a 41mm carb ? as this is what my transfer port areas add up to.

!!!!!!!! I'm very interested in this, as I can see all sorts of waves doing a merry dance in front of the belmouth - almost as if they are all trying to get in at once, but can not, so they jump about while quing up! "really weared to see it".

to recap what do you think of me trying to increase opening by lifting the barrel 0.008 to 0.010 thou, I nearly forgot, "I can actually tell how far down the transfer the charge is goin", approximatly 22.5mm from BDC how do i work out how much earlier I need to open the exhaust port. by this, I MEAN can it be calculated (Trevor/John) ? also I reccon my exhaust is working realy well, as its unberleavable loss of power
if i remove the pipe, and check the power loses, 80% and the torque "but interestingly only above 6000 rpm the figures are the same below this. ?

best regards Derek
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Derek

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Number of posts : 1065
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PostSubject: Re: returning to bantam racing   Thu Mar 15, 2012 12:25 pm

I hope you enjoy looking, and reading at my idiosyncrasies
http://illiweb.com/fa/pbucket.gif

I have shown these before but look a little closer and you can you see the "cracks", !! almost they appear in front of your eye’s, like a big sign you have got no chance "sucker” but all is revealed it’s in the detail “as Trevor puts it”, what I have here is an original set of gears, nothing special. I think a few things would have been different; had Iknow about these issues, it’s not uncommon to see cracks in gears.

One for all those “you will never go back into the deep blue sea, with these in the water, as if these beauties get a hold of you, “ you’re in the kitty litter”, or down the road!! “ this is certainly on the Edge of being unusually!” Typical set of standard Gears, but look closer and see the cracks just waiting to tip you into the deep end. !

im saying check all your gears,! and properly, you will be amazed at what you find..! My dad always said if you cannot count the counter, you ask the counter to count for you.

When I was 21 I came close to a real big one, again I had another off when I was 26, this put me off racing for a good few years, I think it may have been to do with these beauties. only when you check properly is it safe.

I hope you enjoy looking at what I'm upto, all simple and all comes from people in the know and direction on this open Forum,

a million miles from the front boys, I just need some special magic to make it happen, like loose three stone, and gain an equalility in performance from my package is what Im striving for.

please feel free to comment on the photo's, specifically the ports ? what do you think..

http://illiweb.com/fa/pbucket.gif

Hi Trevor
see the transfer duct profile here please comment what you think good bad to big radii too small?























http://illiweb.com/fa/pbucket.gif
[img][/img]


Last edited by bettsd on Sat Mar 17, 2012 11:12 pm; edited 2 times in total
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