REPORTS ON A 1914 HUMBERETTE RESTORATION

[mike6024]

This is what the harley rods look like for 1981 and earlier apparently.

Fits Vtwins:
FL 1941-1981
FX 1971-1981

Features forged and machined H-Beam design of certified 4340 steel with multi-staged heat treatment.
Rod assembly is fitted with Torrington rollers with extruded alloy cages pin and matching nuts. Rods measure 7.440" center to center and will accommodate up to a 5" stroke.

[mike6024]

 

There are both Briggs & Stratton and Kohler V-twins, but their connecting rods are not fork and blade, they are side-by-side, and they seem short. So I don't know if maybe you could use the pistons from these, but you wouldn't want to adapt the connecting rods I wouldn't think. The Kohler V-twin is very common, for riding mowers, wood chippers.

 

[mike6024]

Installing Harley rods in a Matchless V-twin. He used the Harley big end too, and machined it to fit the matchless flywheel. Thought you'd be interested in that part, how the Harley rods are adapted to work in a non-Harley engine.

 

 

[mike6024]

It's interesting how the dude machined the flywheel(s) in that video to accept the new Harley Davidson "fork and blade" rods. It is like a pie-shaped area gets notched out. Then you've got to balance it. Balance it, without the rods of course, but with that new pin, or you might call it the rod big-end journal. It would seem that notched pie-shape area lightens that part of the flywheel, offsetting somewhat the weight of the new crank pin.

[Mike Macartney]

Thanks for all the links and videos. I am sure there must be motorcycle breakers in the UK. Having only owned 'old' motorcycles, mainly pre war, I have never had the need to get in touch with any of them. Even car breakers yards are now few and far between in the UK, as 'Elf and safe tea' (Health and Safety) has done it's best to get rid of them. Most of the more modern motorcycles would have conrods a lot shorter than the V-twin Humberette engine's con rods. Many of the early V-twin engines were 'clones' of the J.A.P. engines John Alfred Prestwich (British manufacturer of engines). I have found a couple of J.A.P. specialists, that I need to talk to, about the availability of fork and blade conrods, but first I need to work out suitable lengths of rods I could use with the stock BMW or Ford pistons that I have got.

 

If you look at the video of the Briggs & Stratton V-twin engine, the side by side conrods need to have cylinder barrels that are offset.

 

The work that has gone into building that V-twin Matchless motorcycle engine is amazing. It makes my efforts at improving the Humberette engine look incredibly easy.

 

HD rods - The dimensions of the rods you posted are too short. I did roughly measure the length of my Humberette rods and wrote the length measurement down in my notebook. I have quickly looked through my book and can't find the dimensions, I think from memory it was about 9" between centres.

 

As I am now working on the front flywheel assembly and have removed the rivets. I haven't posted photos, as it is the same process as previously posted, but a lot easier and quicker, now that I know what I am doing! The recess for the shaft flange in the cast iron flywheel is a lot less worn than the other one.

 

 

The second flywheel, stripped of it's shaft and ready for the holes to be threaded to fit the 5/16" countersunk screws.

 

At present I am making a jig to hold the flywheel assembly in the lathe chuck and waiting for some nylon tipped grub screws to hold the shaft in place in the jig. While machining this jig I went to change the carbide tip in the lathe tool I was using and found that it had broken. I went on the internet to find a new tip I was amazed at how complicated just trying to buy a replacement tip was. I now have to learn about the various tips available. Perhaps I may go back to using HSS! In the past, when using my Myford lathe I have always bought a box of tips, when I bought the tool and have never had to buy tips separately until now.

[JV Puleo]

Mike... I've always used HSS. Generally, these old lathes don't turn fast enough for carbide to do a good job (though I don't know what your lathe turns). I do use some carbide boring bars but that is only because I haven't ever worked out the tricks of using HSS for that job. In any case, HSS works fine on cast iron. In fact, I think it is superior for slow speeds.

[Mike Macartney]

Joe, I think you have the right idea sticking with HSS. I do have a large selection of these HSS cutting tools - so now you come to mention it  - why am I bothering with the carbide inserts?  Although my large lathe does have a number of different speeds. I had a lot of carbide inserts of different sizes and types, that came with the big lathe, I also have about five insert holders, two of which are a LH and RH that I used on machining the flywheels. When I removed one square carbide insert from one of the tools to turn it around, it broke in half. Sods Law being what it is, of course none of the spare inserts I have, are the type to fit this tool! I decided to try and find some replacement insets - easier said than done. It seems a complete minefield! I have spent the afternoon on the internet, trying to learn a bit about them, so I know a little about what I'm talking about, if I try to order replacement carbide inserts. After reading your post I may stick the carbide tools in the draw and forget about them and stick with HSS.

[JV Puleo]

This is another example of how "new" (carbide tools aren't exactly new) is not always better than the old way for this type of work. In the production machine world, where time is everything and profit margins can be very close, running at top speed is critical. For making one-off parts, using what are essentially materials that have been around for eons and the set-up often takes longer than the machining, using the latest and greatest is often a wasted effort. When the Humber was built, HSS was "new". Chances are, most of the lathe tools they used were carbon steel. All of the fantastic machines of the late 19th century were built using carbon steel tools. Machinists tend to be very conservative in adopting new things when they know the old ones work well. I think carbide arrived on the scene in the 1930s but it probably took 40 years before it was the industry standard and then only because the older machines, which weren't suited to carbide tooling were being replaced.

 

Another thing to keep in mind is that HSS is much easier to sharpen and grinding special tools is much easier.  I find it to be a lot more flexible.

[mike6024]

Just for information, the maximum rod length for Harley Davidson is 8.375 inch. For Indian V-twin is a little less, 8.15 inch.

 

HD-BGTWN-08375N  Length = 8.375  Pin end width = 1.060 Big end width = 1.754  Big end bore = 1.6250 Piston wrist pin diameter = 0.927

 

 

[Mike Macartney]

Mike, I received an email that you had posted details of the company who can supply V-twin conrods but when I looked on this post it wasn't here?!?

 

I measured the original conrod yesterday and it is 9.75" between centres. I maybe able to use shorter rods as the BMW pistons that I may use have a lot higher crown height. I need to get my 'drawing head' on and do some sketches and calculations.

 

Joe, Many thanks for the information on the HSS tools and the history. I think you have convinced me.

[mike6024]

The Cycle Salvage Place? http://www.salvagecycle.net/

 

I could contact them and ask what is the longest, used rod set they have. 7.44 inch seems to be the most common. 8.375 would be hard to find, but you could get that new from a specialty supplier. Here is a couple off eBay:

 

8.00 inch eye-to-eye offered at $99 http://www.ebay.com/itm/8-000-Harley-Davidson-Twin-Cam-Connecting-Rods/333171179790?

 

I THINK this set is 7.44, but it doesn't say only $41  http://www.ebay.com/itm/HARLEY-CONNECTING-RODS-SET-FITS-45-FLATHEAD-1932-1973-NEW/112475064818?

 

I delete stuff sometimes, I realize I was cluttering the thread with stuff not too relevant.

 

But anyway, if original is 9.75 that is much longer. 1.75 inches longer than 8.00. I think it would be a stretch to make them work.

Also be aware these Harley rods can have different wrist pin diameters, different big-end diameters, and different big-end widths so you need to check all that. And I think the big-end width may present a problem too. And you will need a correct pin and machine it like the fellow who did with the Matchless.

[Mike Macartney]

10 hours ago, mike6024 said:

I delete stuff sometimes, I realize I was cluttering the thread with stuff not too relevant.

 

Don't worry about that - I clutter it anyway with all my 'waffling'!

 

Before I go into the workshop this morning, I will measure the crown heights of the pistons I have got, to see the lengths of con rods I could use. The original width at the big end is 1-3/4", I doubt if the fork and blade HD conrods will be a wide as this, I could make up spacers to make up the space. The diameter of the big end is 0.975". The small end of the conrod will depend of the pistons I use. I'll post the piston details later.

 

Thanks for your interest and offer of help.

[Mike Macartney]

The conrod length for the BMW pistons could be between 9.075" and 9.315".

[mike6024]

"The conrod length for the BMW pistons could be between 9.075" and 9.315"."

 

So that won't work then, they're not even close I was hoping there'd be an easy answer. Something other than off-the-shelf Harley rods is needed.

[Mike Macartney]

3 hours ago, mike6024 said:

Something other than off-the-shelf Harley rods is needed.

 

Yes, it looks like it. It's a shame, as the links to the eBay HD rods you sent me looked a reasonable price. I'm now trying to find the lengths of the JAP rods used in the Morgan 3-wheelers.

 

Here is the 'jig' I am making for holding the crankshaft main shafts for the final machining of the flywheels and lining up the two halves of the crankshaft.

 

 

Before I finally machine the bore to fit the main shafts of the crank I want to drill and tap to fit six nylon tipped grub screws, that have now arrived. Yesterday, I realised I had not got any taps at 1/4 UNC, now I have to wait until they arrive, hopefully they will be here at lunchtime today.

[Mike Macartney]

Now having the taps for the grub screws, I removed the jig from the lathe chuck, although I would have prefered not to, but there was no other way to drill and tap the holes for the nylon tipped grub screws, that I hope to will grip the mainshaft of the crankshaft.

 

 

I used the drill press to drill the holes and line the tap up for threaded holes. I drilled the hole and started the tap before moving on to the next hole. As the hole positions were not critical, I eyed up the 'centre punched' indentations before drilling first with a centre drill, then a 4mm drill and finally 5mm drill for the threading taper tap. As the hole is 1/2" deep I had to tap again with 'second' tap that came with the set of 3-taps.

 

 

Checking the grub screw fits the thread.

 

 

I then fitted the jig back in the lathe in the same position and machined the bore out, a small amount at a time, until the shaft would slide in. As there was a taper at the front of the shaft, I was able to judge how much metal to take out of the bore by marking with a felt pen where the taper touched the jig, then by taking a 0.005" thou cut, marked the position on the taper again with the felt pen. I could then see approximately how much more metal needed to be machined out of the bore.

 

I don't think I made the bore deep enough, because, as the photo above shows, the shaft would only slide in this far. I then packed up for the day to have a think!

 

This morning, having thought about it overnight. I shall go and paint some marking out blue on the shaft and rotate the shaft in the jig to see if I can find the position in the jig that is causing the stoppage. Another thought came to mind. If the shaft got stuck in the jig it would be very difficult to remove it from the jig. I will have a look to see if I have a smaller diameter long drill that I can drill right through the jig so that I can push the shaft out from the other end using a pin punch, if the need arises.

[JV Puleo]

yes...put a hole all the way through. If you prepare for that problem chances are you won't have it. If you don't, you will!

With a 3-jaw it's a good idea to mark one of the jaws and the fixture and always return it to the chuck in exactly the same place. I suspect that is what you've done. That should minimize the runout that is inherent to all 3-jaw chucks.

[Mike Macartney]

Joe, I did not see your above post until this morning. Luckily, I did exactly what you wrote.

 

 

I found the only long drill I have and drilled right through the jig.

 

 

 

I had already marked one of the jaws of the chuck and made a corresponding mark on the jig. I painted on the 'marking out blue' on the shaft/flange.

 

 

 

After fitting the shaft into the jig and giving it a little twist this bright mark, to the right of the threaded part, showed up. Perhaps I had not drilled deep enough with the large diameter drill that I had used, before starting to bore out the hole to size. I refitted the large drill in the tailstock and drilled in another 1/4" deep.

 

 

I cleaned to swarf out of the threaded holes and then cleaned the inside of the bore.

 

 

These are the six nylon tipped grub screws I bought for locking the shaft/flange into the jig. Never having used these before, I am not sure if they will hold the shaft firm enough to lock the shaft in position, while I machine the flywheel faces. If not, I can always make something to fit into the big end hole and extend to the chuck to work as a 'drive dog'.

 

 

I pushed the shaft into the jig and rotated the shaft, in the jig, by hand, to check if there was any runout. So far, so good! Less than 0.001" run out. By now it was lunchtime and the hottest July day in Norfolk since records began. The hot weather is not doing my breathing a lot of good, all afternoon and evening I was struggling to breath, it was so bad that I didn't join the other 'old boys', at the local pub for our normal Wednesday night get together. This morning, I am a lot better and ready to go and do a bit more work on the flywheels.

[JV Puleo]

That all looks good. When you tighten the grub screws you'll be able to feel the ends crushing slightly...I get them reasonably tight but I've never used them in precisely the same way you are. Saturday and Sunday were out hottest days yet  with the  temperature hovering around 100F (37-38C). I was going to mow but decided it was better to stay in - and the shop is in a basement so it's cooler too.

[chistech]

22 hours ago, JV Puleo said:

yes...put a hole all the way through. If you prepare for that problem chances are you won't have it. If you don't, you will!

With a 3-jaw it's a good idea to mark one of the jaws and the fixture and always return it to the chuck in exactly the same place. I suspect that is what you've done. That should minimize the runout that is inherent to all 3-jaw chucks.

Why do the law of averages always seem to be against us. Like wiring three phase power, you have a 50/50 chance of getting rotation correct yet it seems it more often is incorrect rotation than correct!

[Mike Macartney]

15 minutes ago, chistech said:

Like wiring three phase power, you have a 50/50 chance of getting rotation correct yet it seems it more often is incorrect

 

Yes, it happened to me a few weeks ago, when I put a three phase plug on the surface grinder, that I had recently bought. The previous owner was mean enough to cut the old plug off! In the UK we call it 'Sods Law'.

[mike6024]

When it heats up, I would think you'd spend more time at the pub, not less.

[Laughing Coyote]

Don't the folks in England drink warm beer?  I wouldn't think it would be a good combination on a hot day.  A nice ice cold one or two would be better. 

[Mike Macartney]

13 hours ago, Laughing Coyote said:

Don't the folks in England drink warm beer?

 

If real ale is too cold you can't taste the flavour! A few years ago, I used to trundle up the local on my electric bike every evening at about 5pm for a couple of hours and two or three pints, after playing in the workshop all day. Now, even getting on my bike, makes me puffed out! Perhaps I could use my ride on mower!

 

Finished setting the rear half of the crankshaft assembly up, and machined two faces.

 

 

I used a HSS tool this time and only took off 0.0025" off at a time. The grub screws seemed to hold the shaft OK. This morning I need to try and see if I can machine the face nearest the jig. The problem being that the diameter of the flywheel is too large to let the carriage go underneath it, I don't want to remove the flywheel from the jig unless I really have to. If I can't get round the problem I may wait until I have the two halves bolted back together with the big end journal and then machine it.

 

 

I got fed up with keep on changing my number 2 Morse taper drill chuck from the lathe to the mill. It also has to have a 2 to 3 Morse taper adapter fitted for both machines. I bought this 5mm to 20mm drill chuck with a 3 Morse taper. It looks as if it will also help me to set up the other half of the crankshaft assembly when I bolt the two halves together as the chuck opens up wide enough to hold the thread at the end. When I have got it roughly lined up and bolted I can replace the drill chuck with a rotating centre. Anyway, that's the plan.

 

[r1lark]

Mike, I sure can't offer any advice on what you are doing, since this work is way above my rudimentary machining skills (and skills is probably not even the correct word ) . But I am following this thread enthusiastically, and am impressed with the work you are doing.

 

One thing I am confused about is the discussion about replacing the rods with some other type/brand. Are the original rods damaged or otherwise unusable?

[Mike Macartney]

Thanks for your message. My machining skills were the same as yours before I started this Humberette restoration. Reading Joe's (J V Puleo) post's on the machining of his 1911 Mitchell parts has given me the confidence to try harder and be more accurate with my machining. Previously, I tended to use my lathe for simple machining and the occasional screw cutting. I am enjoying the work and still using this forum for help when I am not sure of something.

 

The conrod set up on the Humberette is a strange one. There is a main conrod and what I suppose you could call a 'helper conrod'. (see photo below).

 

 

As one of the cast iron pistons is cracked I am going to fit more modern aluminium pistons at 0.25mm oversize and thought that if I could, I would try and also replace the conrods with fork and blade conrods, where the conrods both pivot on the same big end journal. It is now looking less likely as I am running out of options of finding fork and blade conrods with the correct distance between centres. (somewhere between 9.25" & 9.75" depending on the pistons I use).

[Mike Macartney]

Did more machining on one of the two flywheels this morning.

 

 

With a bit of 'jiggery pockery' I managed to get a lathe tool to the rear side of the flywheel. I had to go back to the carbide insert tool, that I had used before, as it was the only substantial one I had, that would reach without the tool post hitting the rotating flywheel, when the cutting tool was in as far as it needed to go. Even then, I only managed to take off 0.0025" at one pass, if I tried 5 thou cuts, the tool 'chattered' and I was concerned that the shaft would move in the jig. By lunchtime I had only managed to remove 10 thou with the slow revs and feed rate that I was using. If it stops raining and hailing, I might go and do a bit more machining this afternoon. At least now, with slightly cooler weather, the old breathing (or lack of it!) seems a little better.

 

 

[JV Puleo]

19 hours ago, Laughing Coyote said:

Don't the folks in England drink warm beer?  I wouldn't think it would be a good combination on a hot day.  A nice ice cold one or two would be better. 

 

Cool would be a better word...it's only warm n comparison to the ice cold American version. One of my friends you'd to say it was "room temperature" and the English have the coolest rooms in the world.

Edited July 26, 2019 by JV Puleo (see edit history)

[JV Puleo]

Before you work on the assembled crank I suggest you check and adjust the "trueness" (I'm not sure what the right word is) of the lathe. When working in just the chuck it isn't an issue but when one end is held in place with a center, if there is some taper, it will show up. There are several ways to do it. You can turn a long piece - or a shaft with bigger diameter pieces on each end and measure them or you can use a set up bar and a dial indicator. I've done both - I'll post some pictures later. If you get it within say .002 in 10 inches you are probably as close as you'll ever get. I've never been able to get my lathe to run perfectly but it varies so little it has very rarely been a problem.

[Mike Macartney]

11 hours ago, JV Puleo said:

"trueness" (I'm not sure what the right word is)

 

I suppose "accuracy", or "accurateness",  may be a better? I have done this before with my Myford lathe. I do have a set up bar for my Myford lathe. I can use this on my big lathe between centres. Don't worry about the photos as I know what you mean.

 

A while ago I bought some adjustable feet for my Myford to level the machine and have, as yet, not got around to fitting them. My original idea was that I would put the surface grinder, I bought recently, in the bottom shed, where the Myford and Clarke drill press/mill live. While moving the machines around to fit the surface grinder in I thought I would fit the adjustable feet to the Myford and level it. The plan changed when daughter Fay had two pallets of remanufactured BMW 2002 oil pumps delivered and she only had room for one pallets worth in her Jaymic stores. I let her store them in my bottom shed. I then decided there was room in my garage to fit the surface grinder between the big lathe and the milling machine.

 

When the big lathe and mill arrived they were just put on the concrete floor and not levelled. Should I consider levelling this big lathe as it does seem to rock slightly if I try and pull the chuck round when I forget to take it out of gear?

 

All I wanted to do at this stage of the crankshaft overhaul was try bolting the two halves together with the big end journal to see how accurate I could get it. It will need to come apart again to fit the conrods. I will have to have a think about what to do if I still need to machine the flywheels when they are bolted together. I apologise for 'waffling on a bit' in this post. 

[mike6024]

So when you bolt the front and rear flywheels together using the "big end journal" the two flywheels should remain parallel, meaning the distance between them uniform all around the circumference.

 

What are you trying to do at this point? It seems you are wanting to check that the crankshaft is straight along an axis, now that the front and rear flanges are secured, screwed to the flywheels?

 

BTW, I had been under the impression there was something wrong with the connecting rods, some crack in one of them, or something. But I see now it's just one of the pistons is bad. OK.

 

[Mike Macartney]

10 minutes ago, mike6024 said:

So when you bolt the front and rear flywheels together using the "big end journal" the two flywheels should remain parallel, meaning the distance between them uniform all around the circumference

 

Yes, that's what I am hoping for.

 

11 minutes ago, mike6024 said:

What are you trying to do at this point? It seems you are wanting to check that the crankshaft is straight along an axis, now that the front and rear flanges are secured, screwed to the flywheels?

 

Yes, again, I am hoping that the front and rear shafts are straight and inline. I have lapped in one shaft/flange and bolted it to the cast iron flywheel which I am now finally finishing machining. I still have to do the same to the other half of the shaft/flange and bolt it to the flywheel and finally machine that. I think I have added confusion to my posts by thinking too far ahead!

 

17 minutes ago, mike6024 said:

BTW, I had been under the impression there was something wrong with the connecting rods, some crack in one of them, or something. But I see now it's just one of the pistons is bad. OK.

 

The possible problems all started when I checked the compression heights of the pistons before I took the engine apart. One piston appeared to come up higher up the bore than the other piston. After I removed the two cylinder barrels the conrods looked different. At that stage, I did not realise what the conrods should look like and thought, maybe one conrod had been replaced, I got suspicious of what had been done in the past to the engine. All I could see was the conrods sticking out of the casing and repairs to the aluminium casing where one of the conrods comes out.

 

 

I thought it was best to strip the engine to find out more. I had nobody to ask, as both the previous owners had died whilst they were restoring the car. I knew it had been taken off the road in 1926 and no work had been done on the car until the mid 1990's. According to the two sales invoices the engine had never run since 1926. Although the son of the last owner said his dad had run the engine by pouring some petrol (gasoline) into the float chamber. Perhaps he meant his dad got the engine to 'fire once or twice'?

 

After finding the loose rivets fixing the flywheels to the shaft flanges I needed to sort that out first before I did anymore work to the engine. I still have not found why the compression heights are different in each cylinder. I will have to now wait until I have the bottom end sorted before I refit the barrels and check the compression heights again. It maybe human error and that I managed to get the measurements wrong!

[JV Puleo]

Yes... you should level the lathe. I was astounded what a difference that made in my own machine. You wouldn't imagine how much a lathe bed can twist under it's own weight. If you do level it, it's best to wait a week and level it again because sometimes it takes time for the twist to settle out. You'll need a machinist's level if you don't already have one.

 

Effectively, it's an "assembled" crankshaft. I doubt the flywheels will be perfectly parallel but a few thousandths out will be inconsequential. I wish we know how accurate the original was. With those riveted joints I have my doubts that it was perfect and suspect you are putting it together more accurately than the makers did.

 

I still like the idea of the fork & blade connecting rods, preferably with roller bearings but you are running into the same problem I had looking for con rods for the Mitchell. I am certain there is one that would work but unless you have a huge stock of old rods at hand there is almost no way of getting the dimensions. No one lists rods by their dimensions so you don't know what to look for.

Edited July 27, 2019 by JV Puleo (see edit history)

[Mike Macartney]

13 hours ago, JV Puleo said:

Yes... you should level the lathe. I was astounded what a difference that made in my own machine.

 

Thanks for that Joe, I will give it a go. I did buy a secondhand machinist's level on eBay a few years ago. I have just watched a U-tube video on levelling a lathe using a plumb bob.

 

13 hours ago, JV Puleo said:

Effectively, it's an "assembled" crankshaft. I doubt the flywheels will be perfectly parallel but a few thousandths out will be inconsequential. I wish we know how accurate the original was. With those riveted joints I have my doubts that it was perfect and suspect you are putting it together more accurately than the makers did.

 

At least it is making me more careful with my machining and measuring, rather than my previous efforts of 'that will do' making spacers and other unimportant bits for the motorcycles. The main thing is I am enjoying the work, or should it be called 'pleasure' rather than work!

 

13 hours ago, JV Puleo said:

I still like the idea of the fork & blade connecting rods, preferably with roller bearings

 

So do I. I think I will put a search on eBay for HD conrods and see if any turn up cheap to have a look at. I have read somewhere that somebody successfully shortened a conrod by cutting and welding. I guess the price of having fork and blade conrod made to a special size would be too expensive, looking at the prices that some of the conrod specialist manufacturers charge. At this stage of my machining skills, or lack of, making them myself is out of the question.

 

Thanks again for your help and advice.

[Gary W]

On 7/26/2019 at 7:10 AM, r1lark said:

I sure can't offer any advice on what you are doing, since this work is way above my rudimentary machining skills (and skills is probably not even the correct word ) . But I am following this thread enthusiastically, and am impressed with the work you are doing.

 

I'll Second that!

Following you, JV and Chris throughout your restorations is "must-see TV".....bringing these vehicles back to life with such exacting detail is very impressive. 

I follow you guys, knowing full well I don't have your skills,  BUT,  I do learn at least enough to have a discussion with a local machine shop and understand what they are talking about.  

 

Keep up the great work!  

[JV Puleo]

I have also heard of welding connecting rods. Deciding whether it is practical is beyond my skill level - it would take someone knowledgeable in the engineering aspects of welding to answer that. I wonder if you could use a "Fork & Blade set from a car? You'd probably have to reduce the thickness of the "fork" piece. The RR PIII used them as did a lot of the early V8's like the Cadillac.

 

[Terry Harper]

Mike,

 

When you say that the compression height is different how much difference are we talking? If its not a whole lot You could make-up some by boring the little

end bushing off center providing there is enough material. Remember that with a forged or cast rod blank there is always variation in the center to center distance that's taken

out when the its bored for the bushing and bearings. Another thought is cast a replacement pistons then you can make-up the difference by 

adjusting the location of the wrist pin or leaving the piston short or long to suit.

 

I am not sure if I mentioned it before but there are some gents on your your side of the pond who just completed an amazing restoration of a WW1

Thornycroft Lorry. They couldn't salvage the original cast iron pistons so that cast up a new set in aluminum. The only issue they had was they were

a bit to tight and it would seize up when it got hot. They dressed the pistons down a bit and now it runs great.

 

I would strongly suggest a good beverage and a comfy chair before you head down into the rabbit hole. Its an amazing restoration.

 

http://hmvf.co.uk/topic/9672-ww1-thornycroft-restoration/

 

 

 

Edited July 28, 2019 by Terry Harper (see edit history)

[Spinneyhill]

For some reason Terry's link just brings us back here. Here it is again; I hope this one works.

 

WW1 Thornycroft Restoration

Edited July 28, 2019 by Spinneyhill (see edit history)

[Terry Harper]

1 hour ago, Spinneyhill said:

For some reason Terry's link just brings us back here. Here it is again; I hope this one works.

 

WW1 Thornycroft Restoration

 

Thanks for fixing it!

 

Also, here is a neat video on casting pistons for a 1910 Brush automobile

 

Casting Pistons 1910 Brush

 

Here in the states we have a active backyard metal casting community (I am sure you have the same) who are always looking

for neat and challenging projects. In fact its just such a backyard metal casting  (Peter Grant) who has done all the 

casting I have needed for the big Wisconsin T-head.

 

T

Edited July 28, 2019 by Terry Harper (see edit history)

[mike6024]

On 6/18/2019 at 1:22 AM, Mike Macartney said:

4mm difference in compression height on one cylinder.

 

 

So Mike measured the compression height difference to be 4 mm which is 0.16 inch. More than 1/8 inch, but not too much more.

 

 

Note this picture is confusing because it makes the "short" connecting rod look shorter than it really is functionally. The "short" rod should be off at an angle, I think the angle between the cylinders, and so the wrist pin, and the main big-end pin, and what I'd call the "hinge pin" are all in a straight line.

 

So Mike was going to double check his compression height difference measurement. It is even possible that when this engine was originally assembled the two pistons were different, in the pin to crown dimension, and at some point it got disassembled and put back wrong.

 

BTW, I actually came across some custom Harley connecting rods which were made like this, one long rod and another short, with the "hinge pin." Claim was it was done because it was stronger than the fork and blade. I'll see if I can find it again. So it is not some wild design.