Honing Plates
 

Does anyone use honing plates on re-bored cylinders?

I was going to machine some Biral Cylinders and most of the classic bike racers I know always use honing plates to apply clamping forces before they finally hone.

Probably tricky with Nikasil but does anyone do this with Biral components?

That's a good question. Does Mahle do this on new cylinders? How about LN Engineering Nickies. I bet Charles could give some good info.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/101156-porsche-torque-plates.html

I found this earlier thread which doesn't shed much light but I am reasonably sure that the practice is worthwhile.

I have spoken to someone that believes that Male have a clamping feature on the machine used for cylinder production but I have no proof that this is correct.

It is certainly common practice on Nikasil Motor Cycle Barrels and is a recommended practice on BMW Air Cooled Twin and Harley Cylinders according to my local bike repair shop.

We plan to make a fixture and measure the deformation that occurs when the cylinder is clamped and then make a decison.

Chris,

Use of a torque plate in motorsports circles is a well accepted practice. Will you heat the cylinders to operating temperature as well? My guess is that a perfect cylinder looks like a twisted banana during normal operation-- but only a good gage can tell.

I was thinking about the thermal factors too. It's kind of unreasonable (crazy) to think that we strive for perfection because...once you get a cylinder to a perfect shape in the shop at 70 deg F and with torque plate fixture, you will assemble it on to the case where in the real world, once in operation, it will probably see significant enough variations in temperatures from changing ambient conditions & changing engine loads, not to mention variations local to the cylinder where the case side is probably significantly cooler than the head side, maybe enough to distort the shape by a few tenths. But I'm still all in for getting it as close to perfect as possible. I mean what else are you going to do?

Hi Chris,

We use torque plates for honing all cylinders; Biral and Nikasil.

Its virtually impossible to replicate running temperatures in air-cooled engines, however this is better than nothing, based on what I've seen.

I agree completely with the above comments about temperature variation particularly with regard to variations but to put ion a clamp laod seems to be the minimum practical approach.

The machine shop doing my barrels looks after a number of single cylinder classic race engines and does a significant number of Manx Nortons, they are all honed with plates and clamp loads.

I will buy some gauge plate and make a suitable fixture.

Thanks.

Hi Steve, would you happen to know what sort of distortion is typical when the cylinders are torqued down in the torque plates? I'm getting five thou of an inch out of round and that seems like a lot. They measured round before torquing.

Thanks for any info.

Would you mind sharing more details about the cylinders you're working with and maybe a pic of torque plate? Where are you measuring 0.005" out of round, top, bottom, middle?

Hi, sorry, I guess more detail would be helpful. The cylinders are cast iron from a 2.2litre 1971 911T. The 0.005" out of round is at the bottom and it decreases to approximately 0.004" at the top. I don't have a picture of the set up but it is basically two large steel plates machined to hold the cylinder exactly as it is held in the engine. We used engine case studs attached to the lower plate to fasten the whole thing together, using Porsche washers and nuts. The whole thing is set up in a large Sunnen machine. When I say "we" I really mean the machinist, as I am way out of my league with this stuff. I'm just the slack jawed yokel.

Thanks for any insight.

Thats not unusual for Biral cylinders. Some Nikasil ones distort even more.

5 thou seems to be a very significant amount of deformation and well beyond the conformability of the piston rings.

The the clamping forces generated by the head studs would cause the cylinder to deform to a shape bit like a four leaf clover (4th Order) and also suffer some axial deformation but at the loads involved 5 thou seems excessive and beyond the conformability of the piston rings.

I am not sure what thickness of Nikasil is used on new Mahle cylinders but I believe that 5 thou is typical in the UK and that US Chrome may use 6 thou.

Depending on exactly how the cylinder has deformed you could end up removing nearly all of the Nikasil.

Very Worrying :confused:

Thanks for the replies Gentlemen. These are completely cast iron cylinders from 1971 so I believe that Nikasil was not yet in use. It seems to me that 5 thou is a lot to take off to make it round; presumably under the same clamping force on the engine the cylinders would maintain the new roundness, but I just do not know. Argh.

Thanks again.

Iron cylinders? Those are the most stable ones and generally do not distort that much at all under load.

If I may ask, what torque values are you using and has the wrench been recently calibrated?

We check and adjust our torque wrenches twice a year to ensure that all values are accurate for these alloy engines.

Hi Steve, thanks. We are using a snap on torque wrench which was calibrated last month. The tightening sequence was 11, 17, 23ft-lbs. When we tightened to 8ft-lbs, ovality went to just under one thou.

We set up a cylinder and head on a half case and tightened it down. While we could not measure ovality due to the case webbing, the distortion seemed to be slightly less judging by what measurements we could take.

Here is a dumb question; is 23ft-lbs always 23ft-lbs? By that I mean does it make a difference if you are squeezing the cylinder with a steel plate versus an aluminum head?

Also, is it possible the cylinders have somehow become seasoned after decades of heat cycling, leading to more susceptibility to distortion?

Thanks again,

Gunther

The force applied to the cylinder has little to do with the material of the honing plate as force is force.

The stiffness of the honing plate could have some influence but the stiffer the plate the less the influence.

Steel has three times the stiffness of aluminium for unit thickness and unless the plate is very thin I can't imagine there is a problem.

The 'squareness' of plate could have some effect as variation in thickness will introduce bending into the studs.

The clamping deformation of a single cylinder is likely to have the following shape:

http://i197.photobucket.com/albums/a...e/4thOrder.jpg

With regard to cast iron being affected by old age there is a small amount of truth and a large amount of myth in most comments on this subject.

Grey cast irons do tend to age strengthen at room temperature and this effect can be accelerated by raising temperature.

The influence of age strengthening does help to improve machinability and it is common practice to leave grey iron castings to 'season' for around a month after casting.

After this time the strengthening effect maximises and the material becomes relatively stable.

It is possible that age strengthening could have a small influence on the anisotropy of the cast iron but I would be very surprised if it could cause the distortion you are measuring, I would have thought any difference in Poisson's Ratio caused by this efefct would be limioted to a few microns.

To get an accurate measurement I think you would need to use a SUNNEN Internal Contour Meter in both the unloaded and loaded condition as this would give a good quality map of the cylinder.

http://i197.photobucket.com/albums/a...linderbore.jpg

Hi Gunther,

Chris provided a FAR more detailed explanation than I could ever do,..... :) :) His wealth of education and knowledge is truly appreciated, at least by me.

To answer your question; yes,...torque is torque so 23 lbs-ft is the same, regardless of what you are doing. We use a precision-ground, 4" 7075 T6 aluminum plate to simulate clamping loads with the alloy heads.

I'm not sure why you are seeing so much ovality with the iron cylinders. I would be putting your torque plate onto a granite surface plate and checking to be sure its truly flat & square.

While I haven't needed to resort to this; one of my contemporaries had similar issues with some Birals and finally resorted to torquing the heads and cam towers up and measuring leakdowns with pistons/rings, and re-honing a few times to optimize the results. Needless to say, this was quite time-consuming and only justifiable with his very high-compression race engine.

A check with a granite block might be useful as a quick check, but a more thorough inspection can be done by a grind shop. They can sweep the surface and measure the runout to at least .0001" if not better. They should also be able to resurface the plate as well.

There's a couple in this link. Not sure if there are any closer to you..
Ontario (Canada) Grinding Shops | Grinding services | MFG.com

My quick take on this problem...be advised that you have 4 studs holding the cylinder....so...orient the cylinder in the same way that the engine studs will hold it.
If the cylinder is rotated...it will distort differently from when it is on the engine.
BTW...I have NEVER built an engine without checking and honing with deck plates in the assembly process.
Bob

My experience with torque plates began with learning from an old car engineer in college. His golden rules were get a plate thick enough to not distort, heat treat it properly to reduce internal stresses that will make the plate itself distort over time, and precision grind it. Also have it checked periodically for flatness.