ET: Engine (Twin) Torque Plates and Cylinder Honing

[oexing]

You believe anybody in new engine production companies used torque plates for honing operations ? Not really, wastes too much time and no worthwhile benefits. In case of Vincent muffs the liners lose most of the grip when muffs get operating temps so hard to see any changes in sizes not counting heat growth. But definitely there is a critical matter with out of round case bores due to split joints of case halves and splits off-centers as well.
Another chance to fu** up bores is a blunt hone or Sunnen type hones with just two abrasive shoes plus two "guiding" shoes from copper or bronce or felt wipers. No way to get geometrically correct bores from that design. Real and decent hones got more than four, six and more abrasive shoes and you´d want to have soft bound stones that will wear before they get blunt and then just follow any shape the liner would have. I will not now elaborate on this unless asked for . . . .

Vic

 

[Magnetoman]

Opinions from my engine reconditioning shop are that the Vincent barrels are quite sturdy by comparison to many others.......There are many other things of greater importance to measure and observe when setting up the barrels I feel.

For someone at your machine shop to have made that statement can only mean they've never measured the distortion with and without a torque plate.

I made torque plates for my all-iron 1928 Ariel and for my Gold Star engines. Even for the all-iron engine the torque plate made a significant difference at the top of the cylinder where combustion pressure is highest and where you would like the cylinder to be round. While there are other things of greater importance, I don't see that as a reason for your machine shop to ignore something that makes measurable difference. Especially since it is equally difficult to hone a cylinder whether it has torque plates attached or not.

I didn't quote measurements above because I didn't take the time to look them up, but I have notes of everything.

Another chance to fu** up bores is a ... Sunnen type hones with just two abrasive shoes plus two "guiding" shoes from copper or bronce or felt wipers. No way to get geometrically correct bores from that design.

There are four abrasive shoes and four guide shoes, the hone is only used to remove the final few thou. after boring the cylinder, and the total of eight shoes and stones are in contact with nearly 25% of the circumference during the honing.

I have a Sunnen hone with an AN 600 that I use on motorcycle cylinders. I have a three-point bore gauge that reads to 0.0001" and on the Gold Star cylinder I finished a few weeks ago I measured the bore every 1" along the length to see the effect of the torque plates. If there had been a roundness issue caused by the hone I certainly would have detected it.

 

[Cyborg]

From my limited personal experience with honing cylinders, I can get a bore finish that is shall we say more or less acceptable considering what we are working with here. I guessing those pistons came out of some sort of 4 wheeled medieval device with liquid cooling? I figure I’m ok as long as I remove all but the last tiny bit with a rigid boring bar and only subject my liner to the horrors of a two stone hone for a couple of thou. Admittedly it’s not a device that I proudly display on my shop wall, but I’m not removing material from a thin wet liner that flexes as the dull stones rotate.
There is a rather nice Sunnen hone for sale locally that had a sheltered life in the aerospace prototype world, but so far I’m managed to ignore it in hopes that it will sell quickly.

 

[greg brillus]

We can all make our own decisions about how we restore these bikes........For me to get the barrels torque plate honed is twice the price.......is that a consideration.........well the last shadow I restored cost in excess of $40,000 dollars so you have to think about additional costs when doing this work. I'm sure the factory never had anything like a torque plate.......we have much better pistons and most everything else over what they had back in the day. For all your efforts to make for a better engine, well go ahead and perfect everything as best you can........at the end of the day how well you are skilled at setting up the ignition and the carburetors will have a far bigger overall affect on the engine. Those kind of skills cannot be found so easily..........

 

[Cyborg]

Cost is certainly a consideration and one normally has to stick to some sort of budget/estimate when doing retail work. I can’t imagine how a machine shop could justify twice the price for using the torque plates. It’s basically two plates four studs and some nuts tightened with a torque wrench. I can’t see what would complicate the process from that point on. 5 minutes to install and a couple to remove it. Pistons and rings are light years ahead and personally I would strive to make the cylinder as round and true as possible to take full advantage of that. Equally important to me, is understanding exactly what is occurring. It may turn out that the gain is borderline, but if I don’t know for sure what difference the torque plates make its hard to make a decision about whether they are worth the effort.

 

[greg brillus]

It cost me about 300/400 dollars to make the torque plates and I was using them quite a bit on my earlier rebuilds, but I found that most bikes still spit quite a bit of oil from their breathers for the first 1000 to 2000 Km's or so with each bike differing as much as how the riders use them, this after using the torque plates.......For the last few rebuilds i have not bothered and I can say the difference is not noticeable to me. Given the breathers on these engines is like their cams, pathetically small.......and anything done to improve this is all experimental short of boring a large hole in the cases and using a larger set up like a bevel Ducati, then we have to live with it. I would use the torque plate method if you can, if you weren't so far from me you could borrow mine.......the return postage would be a killer though.

 

[Bill Thomas]

It cost me about 300/400 dollars to make the torque plates and I was using them quite a bit on my earlier rebuilds, but I found that most bikes still spit quite a bit of oil from their breathers for the first 1000 to 2000 Km's or so with each bike differing as much as how the riders use them, this after using the torque plates.......For the last few rebuilds i have not bothered and I can say the difference is not noticeable to me. Given the breathers on these engines is like their cams, pathetically small.......and anything done to improve this is all experimental short of boring a large hole in the cases and using a larger set up like a bevel Ducati, then we have to live with it. I would use the torque plate method if you can, if you weren't so far from me you could borrow mine.......the return postage would be a killer though.

You could always weld a bit of alloy bicycle handle bar to the ATD cover ?.

 

[Sakura]

I find the older I get, and the more knowledge I accumulate, I find myself overthinking things I never gave a second thought to years ago. Back then I just put things together to the best of my knowledge at the time and never had any problems. If you believe everything you read about engine building you wouldn't contemplate attempting it without a King's ransom worth of equipment. Sure, go ahead and chase the minutiae, I bet it won't make a measurable difference in performance. As usual, just my view (after nearly 60 years of engine rebuilding)

 

[Bill Thomas]

And I still run Specialloids with 10 thou' clearance !. Ron and me rode a standard ish Twin some time ago,
At different times of the day, And He was impressed, I said if you ever ride mine , You better bloody hang on !!.
It's in a different world, Too fast for me.

 

[vibrac]

Ten! jeeze I thought I was pushing at six.