Author Topic: Piston choice - Hepolite or JP?  (Read 1295 times)

Online Peter in Aus

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Re: Piston choice - Hepolite or JP?
« Reply #30 on: 05.10. 2018 04:40 »
I fitted JP pistons and rings to my A10 and have had no trouble

Busselton West Australia
49 A7 longstroke
58 A10  SA

Offline cyclobutch

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Re: Piston choice - Hepolite or JP?
« Reply #31 on: 05.10. 2018 08:38 »
Mmmmmmmmmmm - Rush. A favourite back in the day.
Various, including ...
'58 Iron Head Flash Bitza


Online BSA_54A10

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Re: Piston choice - Hepolite or JP?
« Reply #32 on: 05.10. 2018 08:50 »
FWIW JP are by and large a bespoke piston maker.
Any size min batch size is 5.
In order to keep stock of blanks low the gudgeon bosses are larger than sd pistons so they can shift the position of the pin a bit.
We have been supplied 2 of the same pistons made from different blanks so you must specify if you want a matched pair.
The landlord just bought the last 550 cc sloper piston for $ 275.
The down side is he buys his rings from a local ring maker who used to supply the auto industry so generally they are too hard for motorcycles with C I bores.
Fine if you have fitted a steel sleeve. Thus we toss his rings on ebay & buy new ones.
I get mine from Total Seal as I can order them by diameter width & radial depth.
Ask them for A 7 ones & they will have no idea what you are talking about.

John Healy mentioned some time ago the minimum order for pistons out of the Tiawanese factory where all of the aftermarket pistons are made is 2000 pairs and he sells less than 100 pair of BSA pistons a year.
To make the production price economic they need to be ordered in 10,000 pairs which is about 20 years supply world wide.
At $ 100 pair you are looking at 20 different size pistons for A's x $ 100 X 10,000 = $ 20,000,000
Even with the current low inflation you are making a loss on every pair you sell after 5 years compared to what you would have made on a term deposit or government bonds.
So it is uneconomic to get pistons made for stock.
I do a lot of riding but in the past 25 years have only put 84,000 miles on the M20;  45,000 miles on the B40's and about 15,000 on the A65.
In the 25 years I have bought 2 Std NOS Army pistons for the M20 & one piston each for the B40's from George Heggie when he was in Narwee & a set of +40's for the A65 in 1986
To put that into perspective, George traded out of Greenacre for 7 years & has been dead for around 15 years.
Now when I was in my youth and the A 10 was the only transport I bought a set of pistons every couple of years, usually from Joe ( Allparts ) or Doc Kelly ( Doc's Speed Shop ) and both of them have been dead for a decade or more.
There are over 2000 different BSA pistons which unless some one knows a very benevolent millionaire with a bent towards supplying pistons for obsolete motorcycles we are left with paying $ 200 - $ 400 a pair for bespoke pistons, it is just a matter of economies.
OTOH if every one on this list wants to toss in $ 15,000 ( AUS ) we could get a run of each size pre unit A series pistons, any one got space in their backyard for a container ?
Bike Beesa
Trevor

Online RDfella

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Re: Piston choice - Hepolite or JP?
« Reply #33 on: 05.10. 2018 13:34 »
Berger - your piston weights show each pair are pretty well matched - but that the 'other' pair are significantly heavier than the BSA ones. That is of concern, because whilst the difference betwee two of each pair is negligible, the extra weight of the 'others' at almost 60 grams (2 ounces) could have a slight effect on vibration by altering the balance factor.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online RDfella

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Re: Piston choice - Hepolite or JP?
« Reply #34 on: 05.10. 2018 13:41 »
Some very interesting comments turning up.

Agree with Slymo – my 800cc vee twin has modified Fiat 131 pistons. And sand casting a piston should actually be within the scope of a competent DIYer. The pattern required would be fairly easy to make. I recall one sprint bike that was the first locally to achieve 100mph – using a piston made on a TREADLE lathe.

Trev and Musk – I’d expect maybe a 2% difference, but 54 / 65 sounds a lot. If that’s to get smoothness around 5k it must be rough as hell low down. B31’s are 58% and pretty good at that.

BSA-54 –  2,000 different BSA pistons sounds a lot. Even if it’s true, our requirements are far less. As Slymo suggests, the more unusual models cannot realistically be catered for and owners will have to make do. For the rest, I’d guess about 30 models would cover most BSA classics that are actually ridden. Three sizes would be adequate – 030, 040 and 060 – which makes around a hundred. Add in a few models with alternative compression ratios, and we’re still under 200 types of piston. Now we’re not talking pressure die-casting here (something I’m well acquainted with) so I’m surprised someone hasn’t set up to sand cast small batches of, say, 50 of each of the most popular ones. Less popular ones could be cast to order, with machining carried out on an as required basis as orders are received.
Other manufacturers (eg Triumph, Velocette, Norton) made fewer bikes and models than BSA. and many of those would fall into the ‘unusual’ bracket nowadays, so to cover the spectrum of commoner British motorcycles would not be beyond economic feasibility.  Or is that what BSA-54 is telling us JP do?

Sluggo – couple of answers to your queries ..
I agree, different engines need different approaches. I always checked sizes (always found within .0005) and bored / honed to fit. Weights I didn’t bother about unless a race or fast road engine. Quality pistons from the same box are very close. You don’t get paid for doing unnecessary work. A piston from an average diesel engine will weigh around five pounds and the conrod not much less, so a gram here or there is of no consequence. Add to that the need on some to machine the piston crown to get correct bump clearance, and we’re talking ounces, not grams. If a lot of crown machining was required (sometimes including deepening valve pockets) then I would weigh. Only time I would weigh a piston for a single cylinder (motorcycle) is if I was making a change – eg to a high comp piston, which would be heavier and depending on the difference I would want to check the balance factor.
Parallel twin engines were rare in my workshop, but agree that with their susceptibility to vibrate they might benefit from matching. However, if the pistons are of good quality there’s unlikely to be variations sufficient to affect a road bike. I’d be more concerned about the total weight and its effect on balance factor, as vibration is more likely from the latter than the former. If in doubt, the only way is to set the crank up on parallels and check. If going that far, and unless there is a known good balance factor for the engine / frame assembly, I usually modify the flywheel so balance can be altered without dismantling the engine again. Especially useful on newly-designed engines or when a frame has a different engine (eg Triton) when the balance factor can only be a guess.
My present nightmare is a Weslake engine in a sprint bike. By rebalancing I can reduce vibration to almost acceptable levels at low revs, only to be riding a jackhammer at 5,000. Or vice-versa. One of these days it’s going to fall to bits on the start line so I’m currently modifying the frame in an attempt to change frequencies.
Never known a Gold Star rod to fail (not to say some didn’t). The bikes I raced did hundreds of hours on methanol at 13:1, but then I always kept under 6,000 rpm. Best way to ensure rod reliability is not to ding it and cause a stress-raiser. I always protect rods right up to cylinder going on.
Just have no confidence in alloy rods. Never had, but then again if you saw the rough, spindly rods in Jaguar XK and early Aston engines, you’d wonder how they stayed inside either. Usually. I did see one Jag rod outside, but it was being raced at the tim
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online berger

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Re: Piston choice - Hepolite or JP?
« Reply #35 on: 05.10. 2018 16:02 »
RD fella if I use the heavy pistons in an engine I am getting round to building one day *work* *whistle* I am having it all sent away to be balanced, I am dying to know what the other numbers stamped on the beezer pistons means *conf2*

Offline Slymo

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Re: Piston choice - Hepolite or JP?
« Reply #36 on: 05.10. 2018 20:50 »
The happy and sad thing is that as these machines get older and rarer they will become more valuable. There is for instance little problem in buying Brough or Vincent parts but you do need a capacious wallet. A friend with a twenties Norton 18 flat tank has just bought a speedo drive made I believe in the Czech Republic. Very pricey but not a problem when you consider the value of the machine.
NZ

Online Kickaha

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Re: Piston choice - Hepolite or JP?
« Reply #37 on: 05.10. 2018 21:11 »
FWIW JP are by and large a bespoke piston maker.
Any size min batch size is 5.

We can (or used to be able to) order batches of 4 forged pistons for around $1200-1400 NZD from the likes of Ross or JE,  you could get two in standard bore and the other two in the next oversize
1955 BSA Gold Flash
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Offline Sluggo

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Re: Piston choice - Hepolite or JP?
« Reply #38 on: 05.10. 2018 21:53 »
I think i sidetracked this guys thread more than enough. As is typical on many forums, what WAS a simple question spun off into tangents (Im told im really bad about that). 

So, yes,, 2 grams between a pair is significant in my opinion, But I had been thinking for some time of starting a tech thread on blueprinting, balancing and engine design, some which would use some Non BSA examples but all relative and illustrative....

I am certainly not the worlds leading authority on anything, But I DO have a lot of experience in a range of fields and importantly,, I try and find the smartest people out there who are experts, And harvest as much info as I can.   So, I will ask admin If I can start a sticky and add to it, with pictures, graphs and data as well as cover a lot of this material.  I have been looking for a place to park my data from Sir Eddy as well on his methods of blueprinting and I took photos of a BSA Unit motor that was grossly out of dimension so a great example.  I had intended to put this up on BritBike, but Morgan kicked me off!  (Morgan, the real story is far less interesting than what you were told)

In addition, I have some great examples to illustrate this stuff with.  I worked aerospace and product development and process engineering with a range of applications, And I OWN Norton America..  What did not go to the UK to Stuart I have here, Including prototypes, test pieces and ALL the company materials including all the engineering, stress analysis and development work.  (Stuart has given me permission to use this material, and We are using it for education and outreach for our museum as this is an Oregon USA story as well).   I also have access to the technicians who did all this work and doing more interviews as well.
So, when it comes to making a vertical twin I have a lot of resources on hand.

Dont hold your breath for anything overnight,, I move slow, But Ill ask admin to help set something up.
In the interim tell Morgan what he is missing!
Remember that any advice received on a free internet forum is generally worth about 1/2 of what you paid for it.
We overcharge every 3rd customer to pass the savings onto you.
You can have High Quality, Low price, and fast turnaround. Pick any 2, Never all 3 at the same time.

Online KiwiGF

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Re: Piston choice - Hepolite or JP?
« Reply #39 on: 05.10. 2018 22:45 »
Another shameless plug of my post on balancing, in relation to this thread on Pistons it has some info on piston weights, it can be seen the weight of gudgeon pins is also important. JP Pistons were not unduly heavy as some think.

I’ve read over size Pistons can be relatively heavy as the makers just make (cast?)  one size then machine the OD down for each oversize  *dunno*

I fitted std size JP flat tops with the rings supplied over 5 years and 8000 miles ago with no problems.

https://www.a7a10.net/forum/index.php?topic=6086.msg41598#msg41598
New Zealand

Last had an A10 in 1976, in 2011 it was time for my 2nd one.

1956 Flash Frame EA7-168x Eng. CA10 913x, left BSA together for Liverpool, 5th Dec 1955.

B31 “hot rod” (yeah right)

Armstrong Siddeley Whitley for rainy days (with wife).

GL1800 Goldwing not sure why yet

Online BSA_54A10

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Re: Piston choice - Hepolite or JP?
« Reply #40 on: 06.10. 2018 10:36 »
FWIW BSA used one blank for 2 or 3 different oversizes.
And yes there are 2000 different piston sizes.
BSA made a lot of different engines from the winged wheel to the 550cc model H single.

As for machining them to order, way way too expensive as the set up takes a long time even with dedicated machines
Usually the pin is milled flat both inside & out then bored & ground to spec with a final hone.
The piston is then mounted by the pin holes on a mandrel so that it is concentric to the rod.
The piston is then turned to size then ground oval ( where required ) then the ring groves cut.

Lots & lots of set up time & checking time.

Gravity sand casting pistons is not easy to control the filling of thin walls and get a reasonable grain size.
Let alone things like hydrogen adsorbtion which will cause the piston to grow as it gets hot.
Bike Beesa
Trevor

Offline Slymo

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Re: Piston choice - Hepolite or JP?
« Reply #41 on: 06.10. 2018 12:47 »
Burt Monroe cast his own I believe. There is Roger Donaldson documentary  footage of him using a bunsen lamp to melt the alloy and heat the mold. 
NZ

Offline bikerboy

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Re: Piston choice - Hepolite or JP?
« Reply #42 on: 07.10. 2018 15:45 »
If you have not bought any yet I went to TMS in Nottingham for my pistons and I cant remember the make but they were not heppolite.

I have to say they are absolutely excellent 10000 miles later and I have no complaints at all

Online BSA_54A10

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Re: Piston choice - Hepolite or JP?
« Reply #43 on: 08.10. 2018 06:36 »
Burt Monroe cast his own I believe. There is Roger Donaldson documentary  footage of him using a bunsen lamp to melt the alloy and heat the mold.

Ad so did a lot of local racers over here.
We call them Anthony Hordern pistons whose logo was "while I live I grow" and grow the home made pistons do.
Sid reckoned he got 1 good piston out of 5 and remember these are pistons for race engines so running massive clearences.
You can melt aluminium on your stove top, on a lead pot burner, with a kerro blow torch, in an open wood fire.
However if you do not have a reducing flux over the top you will loose a lot of aluminium to dross.
If you do not degass it before pouring then you will get a "special lightweight" piston with up to 5% hydrogen as discreet atoms dissolved into the lattice.
If you are making paper weights or cheap garden furnature then fine ut as soon as the alloy exceeds 200 C these dissolved atoms of Hydrogen start to move through the lattice and they bump into each other to for a Hydrogen molecule ( H2) . However that requires 9 times the space as 2 single Hydrogens and this puts stress on the lattice causing the part to get larger. And by larger it can go tobetter than a 10% increase in size.

So yes Burt cast his own pistons, and if he was lucky probably 1 in 5 cast properly and of those 1 in 5 about the same number would machine cleanly and of those probably 1/2 failed in service.
Back in the day there were a lot of DNF's in every race.
Bike Beesa
Trevor

Online Peter in Aus

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Re: Piston choice - Hepolite or JP?
« Reply #44 on: 08.10. 2018 09:14 »
I don't think I will bother casting my pistons I will just use JP! ;)

Busselton West Australia
49 A7 longstroke
58 A10  SA