Mike Macartney

REPORTS ON A 1914 HUMBERETTE RESTORATION

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The first thing I did when I couldn't find a socket to fit, was look in my draw of 'box spanners' there was nothing in there that fitted. Box spanners, or as they are sometimes are called, 'tube spanners',  often come in handy to use as is, or to modify, when making a 'special tool' for a job. Thanks Ray for pointing it out. 

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I still couldn't figure out the valve opening timings using my plastic disc. So I 'nicked' Janes dressmaking flexible tape measure. Measured the circumference of the 'clutch' flywheel and divided by 360 degrees to the length measurement for 1 degree in mm's.

 

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Taped it on rotated it.

 

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I then went through the process again finding the opening and closing of the inlet and exhaust valves and marking them with sicky labels.

 

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The length measurement's were then taken with the tape for the valve openings and closing positions.

 

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And the results put into my spreadsheet to give the answer in degrees.

 

Actual measurements      
RH cylinder     mm degrees
inlet opens before TDC   7 3
inlet closes after BDC   123 59
exhaust opens before TDC   115 55
exhaust closes after BDC   3 1
         
LH cylinder     mm degrees
inlet opens before TDC (after)   13 6
inlet closes after BDC   115 55
exhaust opens before TDC   108 52
exhaust closes after BDC   0 0

 

Now, this is where I was going to include the spreadsheet that I put in a post, a few days ago by mistake.

 

To get an idea of height of the top of the combustion chamber, above the piston at TDC, I used some plasticine.

 

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It's not that accurate, but I can take some more accurate measurements when the barrels are off the engine. It appears that the piston in the RH cylinder is going further up the bore than the LH piston. I wonder if the odd looking conrod is a different length? We shall see when I get further into stripping the engine.

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I like that...and I'll copy the idea when I finish my pistons. I did measure things as well as I could before the engine came apart but I only had one piston and I was doing it outside, in my yard ("garden" in British). The pistons were cast with an extra thick head so I could adjust the height when I got it all together. You are probably right about the con rod too. I'd check that very carefully. My grandmother used to say "we shouldn't speak ill of the dead" but I'm afraid that work like that gives DIY a bad name.

 

I know practically nothing about cam timing so when I get to that part of the job I'll be pestering you!

 

jp

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5 hours ago, JV Puleo said:

 

I know practically nothing about cam timing so when I get to that part of the job I'll be pestering you!

 

jp

 

As will I... :)

 

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And I’ll be paying close attention 😃

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Here is a little bit on cam shaft timing. Back in the 80's when I was messing about with BMW 2002's I experimented with seeing what would happen if you retarded or advanced the camshaft by one tooth on the chainwheel that drove the overhead camshaft. I only tested the effect on the road rather than on an engine dyno or rolling road. It had the opposite effect of what I thought would happen! 

 

When advanced by one tooth, It gave more torque at a lower rpm.

When retarded by one tooth it seemed to give more power at a higher rpm.

 

At that time I did not have access to the internet. This morning I had a look and found this information.

 

EFFECTS OF ALTERING CAMSHAFT TIMING

Advancing

Retarding

Begins Intake Event Sooner

Delays Intake Closing Event

Open Intake Valve Sooner

Keeps Intake Valve Open Later

Builds More Low-End Torque

Builds More High-RPM Power

Decrease Piston-Intake Valve Clearance

Increase Piston-Intake Valve Clearance

Increase Piston-Exhaust Valve Clearance

Decrease Piston-Exhaust Valve Clearanc

 

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Do your valve lifters have a flat contact surface or is there a radius?  A flat surface has the effect of opening the valve fully for longer.   The longer the inlet is open the more mixture that can be drawn in.  The later the exhaust opens the more time there is for the combustion to work.

 

( Like in a good pub;   the more one can imbibe the better! )

 

One of the tweaks that Austin Seven owners have resorted to in an attempt to improve performance is flattening the radius of the valve lifters.  A further improvement can be made if  slightly  stronger valve springs are fitted.  It is all marginal but something is often better than nothing.

 

Ray.  

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For some reason I don't seem to be able to get rid of this black square (at the end of the post) that is left from trying to delete the table of 'effects of altering the camshaft timing' that popped up again when I tried to make another post? It also won't let me justify the text - strange! I'll just have to put up with it for this post until I can work out how to delete it.

 

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I am sure I posted these photos yesterday of checking the 'flatness' of the area of the welded corner of the barrel.

 

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I'll finish the post now and see what happens when I try to do another post.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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I found out how to remove it. RTFI! Hadn't seen the button that said 'clear editor'!

 

By way of a change, here are some more photos from the coach trimmer.

 

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Photos by Paul Moore of Moores Trim http://www.moorestrim.com/

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On ‎6‎/‎3‎/‎2019 at 5:30 PM, R.White said:

One of the tweaks that Austin Seven owners have resorted to in an attempt to improve performance is flattening the radius of the valve lifters.

 

Ray, I think they are curved, but I haven't quite got that far yet.

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On ‎6‎/‎4‎/‎2019 at 10:45 AM, Roger Zimmermann said:

Mike: you have the ability to play with cams and pistons

 

Roger, I think PLAY is the appropriate word! I am thinking - I have "opened a can of worms" taking this engine apart. I seem to be having a lot of, thinking time, and not much action with the engine at present!

 

Does anybody out there have any knowledge or experience of Harley Davidson conrods (I may have to replace a conrod or both of them) and Eisemann magnetos. I am also a bit puzzled about cone clutches as I have never had one apart before. Should the engine come away from the gearbox with just undoing the bell housing bolts?

 

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The Eisemann magneto is a 50 degree anti-clockwise when viewed from the front. This is all that's left of the mag after the last owner changed it to electronic ignition with two coils. I think the type is WGJ2, I searched the web but nothing with this number came up.

 

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I am wondering if there is something else I need to undo, apart from the bell housing bolts to pull the engine away from the gearbox?

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If you change either connecting rod it would be best to change both. Balance is critical and I'll bet those two rods don't weight anything like the same amount. They understood this in the period but with slow turning engines, it was not as important as it was as RPMs increased. If you want to maximize the horsepower, balanced rods and pistons will be a big help.

 

As to the clutch - there can not be any solid connection between the clutch and the flywheel other than the pilot shaft so I suspect the flywheel will come off with the engine and the clutch will stay attached to the transmission. Cone clutches have an undeserved reputation for being fierce. The usual problem is that they are out of balance and/or there is wear in the pilot shaft or the bushings that they run in. All that weight spinning, if it is running out at all, makes a difficult clutch but when properly set up they are no different than single plate clutches. RR used a cone clutch on the Silver Ghost and I've never had one that was difficult - but it was extremely well made.

 

One major ongoing problem I have with replacing parts is that dimensions are almost never listed. People have a piston for an X or a rod for a Y but they don't know what the dimensions are and, more often than not, don't know how to measure them (or don't want to). The interchange books aren't much help either and nothing is much help when working on something really old or obscure.

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14 hours ago, JV Puleo said:

If you want to maximize the horsepower, balanced rods and pistons will be a big help.

 

Thank you Joe for the information. With flywheels, is there any benefit in lightening them to make the engine a bit more 'revy' I haven't got that far yet but, this engine has large heavy flywheels each side of the con rods. I know from my vintage motorcycle experience that heavy flywheels were used, presumably to make the engine smoother running?

 

14 hours ago, JV Puleo said:

As to the clutch - there can not be any solid connection between the clutch and the flywheel other than the pilot shaft so I suspect the flywheel will come off with the engine and the clutch will stay attached to the transmission.

 

Thanks for that, I'll have a go getting the engine out today and try and leave the transmission in the chassis for the time being.

 

Looking down the gap between the alloy castings at the big end of the LH con rod, with a torch, there seem to be lots of ball peen hammer marks on the con rod just above the big end. I am interested to find out why, hopefully, I will find out when I get the engine apart?

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I would expect heavy flywheels to make the engine smoother and less responsive, i.e. it will be slower to rev up, or down, than without the heavy flywheel. Centrepetal force also applies a force to the mounting making it hard to rotate at 90o to the wheel rotation, so perhaps damping vibrations. I think. That physics was a long time ago.

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Posted (edited)

Spinneyhill is spot on. Using heavy flywheels is actually a holdover from steam engine practice...balance is much more important. They couldn't do dynamic balancing and had to rely on all-over machining to achieve similar results. It could be good but the added labour meant that only the best machines got this treatment . With a cone clutch, the flywheel is usually the female portion of the cone so there are limits to how much you can reduce them. I'm not certain what is going on with the Humberette...the flywheels adjacent to the rods are much more motorcycle practice.

Edited by JV Puleo (see edit history)
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Thanks Guys, that's what I thought about the flywheels.

 

I got the engine out this morning, but have yet to split the crankcase. Knackered now, I'm getting too old and decrepit for this type of work. I had to get help to move the engine crane into position, as I ran out of puff! 

 

I had to take the springs off the clutch to get the engine away from the gearbox. I'll post some photos later, but I may need an afternoon nap first! I think I should have disconnected the clutch further back on the gearbox. I'm glad I did take the clutch springs off, as they were hiding yet another 'bodge'.

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More measuring on the cylinder barrels, to find out the distance between the top of the piston and the highest part of the combustion chamber.

 

Having previously measured the distance between the piston top and the outside top of the barrel, I needed to find the thickness of the wall between the combustion chamber and the coolant chamber around the barrel to complete my calculations.

 

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I found a length of brass bar, that I put up the barrel under the hole, where the screwed blanking plug screws in between the coolant jacket and the combustion chamber.

 

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I then measured, with a depth gauge, the distance between the top of the brass and top of the thread, where the blanking plug screws in. I took the measurements in 4-places and averaged the results. I forgot to take a photo of the measuring!

 

Next job to start taking more bits off the engine before I remove it from the chassis.

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Measuring the length of the Humber V-twin water cooled barrels.

 

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This is the blanking plug that screws in above the piston centre and blanks off the waterway from the combustion chamber. In the top of the plug is a threaded hole, into which the outer blanking plate is screwed to seal off the waterway from the outside of the barrel.

 

I had been thinking how I could measure the bore length. The only place at the top of the bore that was visible, through the removed valve covers, was inaccessible to get any sort of straight edge in to enable me to measure to it from the bottom of the bore. The reason for needing this measurement was to establish how far up the bore the original piston was on top dead centre so that I could establish how much extra crown height a replacement piston could have.

 

I had a look in for a length of bar that I could fit a small right angle to, so this bar could be held above the lip to measure the bore length. I then spied a threaded rod and thought that may work.

 

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I screwed a nut on one end to 'lip over' the top of the bore where it opened out where the valves were.

 

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Then screwed another nut on the rod and screwed it down until it touched the bottom end of the bore. (by the way the loop is on the camera I am holding in my left hand!).

 

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I then read the measurement between the nuts on a rule. As there is a lip at the bottom of the barrels I measured this distance with the depth gauge part of my Vernier and subtracted it from the bore length measurement. Both bores of the right hand and left hand barrels, measured with the rule were the same length 6-13/16". The lip on barrels was slightly different by only 0.028".

 

The reason for all this measuring is trying to work out why there is so much difference between the measurements of the heights between the combustion chamber top and the top of the pistons at TDC. The difference between the two is 0.157" (4mm) which is a hell of a difference. I think that it has got to be a problem with one of the conrod lengths?

 

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While I was measuring I put the Vernier on the width on the small end. This is the suspect con rod. (35.5mm = 1.399")

 

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This is the conrod that I think I the original. (34.8mm = 1.370") Only 0.029" difference.

 

Another measurement, not very accurate at all, was to see the height difference of the gudgeon pin (piston wrist pin) above the aluminium casing.

 

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LH side of the V-twin if viewed from the driving seat.

 

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RH side. You can see the gap. Time to dig deeper into the engine!

 

 

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At the moment I don't feel much like a detective! I think I need to put all my findings into a spreadsheet, rather than my note book. Looking through my measuring notes it all looks a bit muddled at present.

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Ah... a "tape measure". I have one in the shop and use it fairly often. It's great for measuring the length of belts and the distance around sheaves. My late mother gave me mine - she was a lifelong practitioner of the "needle arts" and High School Home Ec teacher ... she made all sorts of clothes, including a lined duster for me. In fact, she did just about everything except knit - which she never liked although she could do it.

 

I have a similar problem with the Mitchell because at some point someone has "skimmed" the flywheel so there are no marks left. I'll have to calculate them and add them when the time comes.

 

I don't think the problems with this engine are exceptional. In a hundred years, even if it wasn't on the road, its had a lot of time to be mucked with. Most importantly, until quite recently it was completely worthless so it (and a lot of other early cars) did not attract the attention of the top end mechanics. There is a Talmudic saying I particularly like that goes "every misfortune is an opportunity." I often think of it when things go sideways.

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Posted (edited)

Nice quote Joe, We old car guys are firm believers in the truth of that saying, (every misfortune is an opportunity).  Joe is doing a terrific job making a silk purse out of a sow's ear with the Mitchell engine.  What a nice opportunity out of the misfortune that befell the Mitchell.  Mike, I am most anxious to see what your determination is on the internals of your engine.  When you get done with your rebuild improvements, the Humberette will run better than a Swiss watch and pull better than a JD Harley Davidson!  I am interested in seeing whats up with the bottom end. Keep up the Sherlock Holmes attitude as you proceed.

Al

Edited by alsfarms
addition for clarity (see edit history)
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1 hour ago, JV Puleo said:

There is a Talmudic saying I particularly like

 

Not only am I learning more and more about machining from you, I'm learning the meaning of words and expressions that I haven't heard before. I had to look this one up.

 

54 minutes ago, alsfarms said:

the Humberette will run better than a Swiss watch and pull better than a JD Harley Davidson!

 

I very much doubt it. From where I am at the moment it looks a long way from even running! The company I contacted about overhauling the magneto said they are not taking anymore work on until they have got rid of the backlog they have. Apparently, they are getting far more mags coming in than are going out! I have spent a lot of today catching up with paperwork and trying to learn a bit about balancing V-twin engines. In they UK they call June, 'Flaming June', because it is often very sunny and warm. Today it is cold, windy and very rainy, all very depressing.

 

I am wanting to split the flywheels to get to the conrod and crank pin. Before I do that, I need to think about how to mark it, or make a jig, to make sure that when it gets put back together it is in the correct place. I have had this problem before, on motorcycle engines, I have worked on.

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Here is a drawing showing valve timing on a 4-stoke petrol (gasoline) engine, it may help some get their head around it.

 

valve-timing-diagram-of-4-stroke-petrol-engine.jpg.9697e369edf115681065fd3c47ef993b.jpg

 

 

 

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