Which pistons are available for my ariel

[robin.parker]

Nev, I quite agree that "someone" should get some made, I know that Omega are happy to do just that, if "someone" could stump up £3,500 or thereabouts for the tooling costs, and then order a batch of 40 or 50 for about £45.00 each, which is all a bit of an ask. On the positive side, Omega would be happy to make such a batch comprise of an assortment of sizes ( and oversizes). We can hardly expect the Club to fund such an enterprise. A major UK supplier of Ariel parts ignored my email; at one time Thorntons seemed interested, but that faded away. Maybe a well off member, or group of members would take on the task, but then there is our wonderful economic climate to consider!! Thanks for your interest. Robin.

[nevhunter]

Robin it's just that there has been a shortage for a least 10 years. I guess there is an ask factor, but the lord looks after those who look after themselves (they say). The VH is a motor that needs a good piston. If you use the same pattern for oversizes they get pretty heavy.
We could settle on a comp ratio around 7.5 (say). There is not an alternative, that is "just right" as far as I know and I have been looking for a while.
Perhaps clubs worldwide could contribute, or individuals from clubs.
i believe the american suppliers that I mentioned can provide a good product. You would want a good lightweight gudgeon Pin as well. (tapered bore) Nev

[keith.hodgenia]

The club did a good job with square 4 conrods and many other spare parts so there is a president for a large capital outlay. While the club spares section is for the benefit of members, they could be sold more widely with a premium added.

[john.nash]

Nev, I quite agree that "someone" should get some made, I know that Omega are happy to do just that, if "someone" could stump up £3,500 or thereabouts for the tooling costs, and then order a batch of 40 or 50 for about £45.00 each, which is all a bit of an ask..

Is that £3.5k for tooling costs PLUS 50 pistons @ £45 each (i.e. another £2250) for a total investment of pushing £6K ?
Which is about £115 per piston to start with ??


I have spoken to Peter Kemp (a few months back) and he feels we'd need to be testing samples before parting with that sort of money and, to be fair, he's probably right. Is it likely that we'd get sample pistons without the paying for tooling first ?

I am not sure the club would want to be taking the hit for tooling costs/testing without some sort of exclusivity on the product, either.
If the club has to recoup it's tooling investment, by adding a bit to each piston, then having the pistons available to traders/individuals at the manufacturing cost would mean we'd never move them (and essentially means that the club takes the hit for all the investment and testing).

I'll mention this to Kempy, again, next time I speak to him.
I'd be prepared to chuck sample pistons into my 500's and run them around, and I imagine that others would, but that is the easy bit.

[robin.parker]

John, I'm afraid you've got that right, £3,500 for tooling, plus the cost of about £45.00 per piston, so the FIRST batch would indeed cost about £115 each. And, I'm afraid there is no likelihood of the only manufacturer I know of being prepared to make any for testing.
They trade on their reputation, tricky situation or what!
Regards,
Robin.

[nevhunter]

At those costs you would be well advised to be cautious. As far as testing is concerned there is enough design data available to just decide on a style. Ie solid skirt plain oiston. You don't have to reinvent the wheel here. You would use the latest alloys and metal 3 piece die casting technique which is almost universal, unless you are going down the forging path. (Not necessary).
The OEM piston industry in Australia is virtually non-existant and even Mahle is done in China. Nev

[keith.hodgenia]

The costs being talked about here is comparable with what Drags are asking.
Are their pistons now in short supply or are they less than ideal for some reason?

[brenton.roy]

Hi Keith, the drags pistons are JP's. They need lots of clearance and tend to swell a bit. The gudgeons are very heavy, as are the pistons, so some riders complain about poor engine balance and vibration. My VH has a JP, actually its second, which has only done a couple of thousand miles, and it (piston and bore) is shagged due to seizing. I cured the problem by honing the bore to worn out, which works, but is hardly the point.
I would happily part with the money for a good piston - particularly a Wiseco, in my opinion the best of the quality brands Nev mentioned. Over many seasons of racing (another make of bike), I didn't have a single piston problem. Better quality pistons mean smaller tolerances, longer life and less issues, and are in my book therefore more econonical.
Another solution is to have a batch of Harley pistons (as proposed in other posts) machined to suit. Maybe the club could explore this or both options?
Brenton

[robin.parker]

It's best not disregard Omega, they are good enough for the Vincent OC and Ducati (both MotoGP and WSB), so they really do know their business (they are not touting,by the way). Perhaps we should consider forming a "sponsor group" to fund the job someday. What is certain (in my opinion) is that as a solution, JP, for a VH, are slightly better than nothing.

[david.anderson]

I was doing some reading on the net in the Velocette Owner Compendium and I came across a part that said that Omega pistons were most unsatisfactory as they expanded too much. JP was the preferred piston in the Velo. Quite different to the general comments here which made me think that it would be good to measure the expansion of different pistons.
I decided to go through some of my old pistons and measure them (temperature 15C), then I put them in the oven at 250C for 1 hour (at which time my wife arrived home to find the house full of smoke) and I measured them again. Unfortunately my JP and Omega pistons are in running engines but I will do the same with them next engine strip and will include at least one piston from the first batch to ensure consistency. (My oven dial was set to 250C but was not checked with a thermometer.)
The expansion from 15C to the oven set 250C was as follows, measured at the bottom of the skirt at 90 degrees to the gudgeon. All pistons are used unless marked otherwise
Original Ariel VH6.8 piston +.012
Aust Polson VH7.5 +.011
Aust Diecut Y alloy VH7.5 +.014
Aust Cartledge VH10.5 +.012
Original Ariel VB +.011
Original Ariel VB split skirt +.012 (new)
Heplex NH10.5 +.015 (new)
Of the used pistons the Diecut Y alloy expanded the most while the Polson expanded the least. Both of these are former Australian piston manufacturers.
The expansion of the split skirt VB piston (which is exactly the same as the other VB piston but split) surprised me as the split extends from the oil ring through the bottom of the piston so I had expected a lot less. I am about to have a cylinder bored for this piston. Quoted clearance is .001 per inch of bore.?
Likewise I am soon to have an NH cylinder bored for the 10.5 to 1 Heplex and it expanded more than any other which is even more surprising as it is the smallest piston. Possibly the new pistons will expand less when run in? Anyone got anything definitive on this.
Also anyone got a used JP and/or Omega that they could heat in an oven alongside the original VH6.8 piston and measure the expansion as I hope not to strip either of the engines that I have fitted with those pistons for some time.
David