Another Radial - this time 18 Cylinders

[stevehuckss396]

Man oh man does that look sweet

 

[mayhugh1]

I've been working on the design of the oil system components including the oil pump, transfer tubes, and sump. I was hoping to use the exact same components that I used in the 9 cylinder engine, but the CAD modeling I've been doing the past several days tells me that sump will have to be significantly modified due to avoid interference with the rear row of cylinders. In this engine the oil pump is in the middle of the engine and it pumps oil to the front and rear crankshaft sections. The sump is located toward the rear of the engine and this means that return oil from the front bank of cylinders will have to travel over the lower cylinders of the rear bank in order to get to the sump. This compounds the oil control issues for the lower cylinders in the rear bank. Therefore, I'm trying to make the return path as free-flowing as possible by opening up multiple passages through the crankcase and enlarging the sump inlet tube. I don't yet have the sump fully figured out.
I've got enough of the oil pump designed, though, to start making parts for it and so I'm taking a break from the CAD to get back into the shop to make parts. I'm starting with the pump shafts and gears so I can use them to test their fits in the pump body while I'm machining it. These gears will be identical to those in the 9 cylinder. When I originally cut those gears I actually created lengths of gear stock from which I sliced off the gears. I have enough of those stocks left over to create the gears for this engine. The first and trivial photo shows the turning of jone of the gear shafts. What I will be doing later is using the tooling marks left on the ends of the shafts in these operations to find their true centers after they are located in the pump body in order to accurately machine the cavities for them.
When I sliced off the larger drive gears, I forgot to ream their center holes and so I had to re-chuck them in the lathe. The third photo shows a shop-made tool I use to align thin parts in my lathe chucks. In use, the carriage is slowly moved toward the headstock while turning the spindle over by hand and iteratively tightening the chuck until the bearing consistently rotates against the part. It is not difficult to get the part perpendicular to the lathe axis to within a tenth or so.
In the oil pump I want to keep the clearance between the gears and their pocket walls to less than .0015", but I also want to interpolate the pockets in the pump body using my Tormach. After Loctiting the gears to their shafts I trued them in the lathe for 0 run-out. My Tormach has .0005"-.00075" backlash and so I practiced on a piece of scrap to figure out how I could compensate for most of it and end up with a truly circular pocket of the precisely correct diameter and location. The process I ended up with will be duplicated later when I machine the actual pump body. For now, I'm creating a fixture that I will use to cross-drill a hole through the gears and their shafts for locking pins.
The last two photos are pictures of my shop. When I built my shop many years ago I injured my back and spent several months recuperating from back surgery. My shop ended up pretty close to our rear patio door and according to my wife it was an eyesore. So, I created what I called my dry aquarium. While I was unable to do any heavy lifting, I drew and cut all those sea creatures from 16 gage steel on my plasma cutting table. Each is attached to the Harding-board siding with it own screw anchor(s). Later, when I was fully recovered, I bought a shovel and dug a 1200 gallon pond on the backside of my shop. The fish, turtles, and frogs in this one, though, require feeding and a lot more maintenance. My wife and I spent the next seven summers landscaping what was left of our backyard. I'll post more pictures of our landscaping project as this project
progresses. - Terry

 

[petertha]

...After Loctiting the gears to their shafts I trued them in the lathe for 0 run-out. ... I'm creating a fixture that I will use to cross-drill a hole through the gears and their shafts for locking pins.
- Terry

So the first loctite application is intended to stick the gear to the shaft with enough retention that you can touch them up on the lathe? What loktite do you use for this?

Re the cross drill & pin business, assume the pin is centered through a tooth 'valley', into the shaft. Do you continue part way into the other side of the gear but dead-ended in the hub part? Will you use tapered pins or straight segment?

Nice pond!
-Peter

 

[mayhugh1]

So the first loctite application is intended to stick the gear to the shaft with enough retention that you can touch them up on the lathe? What loktite do you use for this?

Re the cross drill & pin business, assume the pin is centered through a tooth 'valley', into the shaft. Do you continue part way into the other side of the gear but dead-ended in the hub part? Will you use tapered pins or straight segment?

Nice pond!
-Peter

Petertha,
I use 620 bearing retainer. And yes, the pin hole is centered between two teeth and the hole is drilled completely through to the other side of the gear. This gives me twice the shear strength and also allows me to easily remove the pin during the fitting process before it is loctited in place. Only the pins in the four small pump gears are loctited. The two large drive gears which will mesh with the gear on the crankshaft and drive the pump gears are pinned but not loctited since they will have to be removed should the pump ever need to come apart. The pins in these gears will be kept in place by the meshing action of the crankshaft gear. If the pins tend to move outward they will be driven back each revolution by a tooth on the crankshaft gear. I'm using straight 1/16" dowells for all the pins. The purpose of the drilling jig is to make sure the hole that starts betwen two teeth also comes out between two teeth on the other side. - Terry

 

[mayhugh1]

The oil pump body is sealed to the center bearing with eleven 4-40 SHCS, and so the first step is to drill and tap these holes in the bearing using the fixture plate I originally created to machine the bearings. Three jackscrew holes were also drilled and tapped to later help separate the pump body from the bearing. Most of the mounting holes are symmetrical around the y-axis so the part can be flipped over and still be secured to the fixture plate. The pump body, itself, starts out life as a 1/2" aluminum plate glued to a piece of 3/4" MDF. I spot drilled the center of the plate and used it as a reference point to press in phosphor bronze inserts that will be used for the gear shaft bushings. The bottom surface of the pump body is first milled flat; and then the mounting holes, center hole, and outer perimeter are machined. The Chaos Industries guys included a port in their body to measure the pump pressure. I don't think it's a worthwhile feature with the drip-feed from the oil tank needed to control oil flow into the engine, and so I didn't include it on my version.
The pump body with its milled bottom side down is then bolted to the bearing and fixture plate, and in two separate steps the mounting holes are counter-bored for the SHCS. The top surface is then milled to its finished height. It is very important that the top and bottom surfaces of the pump body be parallel to one another since the gear shaft holes will be drilled/reamed from one side and the close fitting gear pockets will be machined from the other side. Even though there are eleven mounting screws securing the pump body to the bearing, these threaded fasteners can't be relied upon to accurately align the holes for the gear shafts to allow minimum clearance between the gears and their pockets. Therefore, holes for three close-fitting dowels were match drilled and reamed through the pump and center bearing before the four shaft holes were machined. After doing this, the jack screws mentioned previously are absolutely required to separate the two parts.
Eighth-inch oil passages are drilled into the the ends of the three arms of the pump. The transfer slots were used to indicate the part vertical in order to center these holes over the transfer slots. I wedged a 1/8" gage lock into the transfer slot and used it and a dial indicator to get each of the slots truly vertical. The scavenger intake port at the bottom of the pump is also counter bored for an o-ring sealed connection to the sump drain through the crankcase wall.
The pump was then removed from the bearing, flipped over, and secured back onto the fixture plate where the gear pockets were milled using the machining parameters derived earlier when making the gear shaft cross-drilling fixture. The spindle microscope was again used to center the spindle over gear shafts. The final step will be to match drill the two pump ports through the crankcase side wall. The pressure input and scavenger output ports are bored and threaded for transfer tubes with banjo fittings that connect to the oil tank through flexible lines. These operations and the oil return passages still need to be done on my nearly irreplaceable rear crankcase section. I'll likely procrastinate, though, and start on the sump. -Terry

 

[Davewild]

Amazing work, I love it!!!

Dave

 

[mayhugh1]

The transfer tubes are the interfaces between the external flexible oil tank lines and the internal oil pumps. They provide a (hopefully) leak proof connection that can be adjusted at final assembly to route the oil lines free of interference to the rear of the engine. It might be tempting to rig up something quick and dirty here since they
will eventually be covered up with a maze of tubing and wiring, but I like to pay attention to detail in hidden areas like this. My 9 cylinder used tubes similar the ones that I'm making for this engine, but changes are needed to accommodate a new cylinder design (similar to the one used by the Chaos guys) that I plan to use. I started with some 1/4" flare unions that I bought from a local Lowes. I cut off a pair of flares and turned spigots on one of their ends for soldering into the banjo fittings that I machined. The banjos and their locking nuts were all machined from a 1/2" thick brass block glued down to a piece of MDF. I added grooves on either side of the shaft holes in the banjos for a pair of o-rings to seal the oil path at the rotating joint. This is necessary because my modeling shows I have limited access for a wrench after final assembly to tightly torque the fittings to eliminate leaks. The tubes, themselves, were turned from some 303 stainless drops I had in my scrap box. The ends of these tubes are threaded and screwed into the pump body through the wall of the rear crankcase section. To insure perfect alignment, the oil pump and center bearing were temporarily assembled into the crankcase and the pump and crankcase were match-drilled and threaded. The crankcase wall was then bored to match the larger o.d. of the transfer tube body for added support for the transfer tubes which protrude outward from the crankcase. Since I was already machining on the rear crankcase, I decided to finish up the oil flow path through it. I machined two slots as low in the center crankcase section as I dared in order to move the oil from the front crankcase section as quickly as possible into the sump. I also drilled the holes for the oil sump. I was able to double the flow area into the sump compared with my 9 cylinder as this will be needed for an additional 9 cylinders. I'm relieved that this completely finishes the machining on the rear crankcase section. It is a very complicated part and screwing it up at this late date would probably be a show-stopper.
I was able to do some preliminary testing testing of the oiling system by squirting oil into the intake transfer tube and manually spinning the crankshaft with the front crankcase and crankshaft sections added. Oil freely flowed out the oil ports in the front and rear master rod bearings. When I finish the sump I will block the rod bearing holes to make sure oil is finding its way to the front and rear bearings. - Terry

 

[petertha]

Can you elaborate on your technique of (I think) inserting solid bushing material into the aluminum blank, then some in-between part machining steps, then eventualy finish drilling final holes in the bushings.

I have a hunch its so you dont have to insert a finicky finished bushing 'ring' into a hole & thus maybe better dimensional control between shaft centers, is that it? Is the bushing material locktited in the aluminum?

 

[mayhugh1]

Petertha,
Yes, you're correct. Pressing in the slug first eliminates any chance of distorting the finished bushing (if pressed in) or getting it off center (if slip-fitted and Loctited). My technique is to square up one corner of the rough workpiece so I can accurately touch off x=0,y=0 and then locate and drill/ream the holes for a light press-fit of the bearing slugs. I do Loctite them in place. After an overnight cure I re-find my zero reference and then machine the bushings in place. It isn't a big problem if the part has to be re-referenced for the machining since if the bearing ends up a few thou off center from the slug, it won't be noticeable either cosmetically or functionally. The part always looks better than if the finished bushing is fitted since the Loctite fills in any imperfections between the slug od and the workpiece id and after being fly-cut the workpiece looks like a single piece of metal. - Terry

 

[mayhugh1]

The oil sump on my 9 cylinder was a major pita because its construction included being permanently soldered to the crankcase before verifying the completed assembly was leak-free. Some who have built this engine have come up with ways of making it detachable, but at the end of the day more points of failure were added and the result didn't look clean.
My original vision for the sump on this engine was a nice cylindrical body with hemispherical ends - one of which would be unscrewed to drain the sump. My CAD modeling, however, showed this was not going to happen. The front of the sump is up against the lower front-row cylinder while the rear of the sump is very close to the intake pipes. The minimum body length is set by the locations of the pick-up and drain tubes in the rear crankcase section and these are fixed by the geometry of the crankcase. So, there isn't room for my spherical ends. After assembly there will be no access to either end of the sump which means the drain will have to be located at the bottom of the sump. The Chaos Industries realistic-looking cylinder/head design that I want to use further complicates the sump design and even affects the final assembly of the engine in this area. I've carefully studied the 500 online photos of the Chaos engine construction, and there is not a single photo showing a sump. They may not have used one, and this may be one of the reasons they opened up their main bearings to create a single common volume for the oiled components within the engine.
The sump design I came up with is shown in the photos. It consists of six individual pieces. The drain plug screws into a bung which was soldered to the bottom of the main body. I cut an o-ring groove under its head to seal against leaks. A socket head set screw was embedded into the head of the drain plug so a small hex wrench can be used to access it. There won't be any room for my fingers in this area after the engine is assembled because the drain plug sits in between the intake and exhaust pipes of the front row bottom cylinder and, in fact, nearly touches them. My modeling shows that removing the plug will probably be awkward even with the hex wrench. I added a magnet to the inside end of the drain plug to collect ring debris during break-in as I did with my 9 cylinder. The front of the sump body is angle-cut to clear the compromise envelope of the cylinder/head combination that I plan to use. The narrowed area in the center of the body is needed to clear the flanges of the adjacent rear row cylinders when they are inserted into the crankcase over their studs during assembly. I didn't have room at the rear of the sump for my hemispherical end, but I was able to make it elliptical. It is an o-ringed screwed-on part rather than soldered just in case I ever need to get into the sump to clear a blockage. The bung for the drain plug was soldered onto the bottom of the body with high temp (Sn5-Pb93-Ag2) solder. For good measure, it was also pinned with two 1/16" dowel pins. The pick-up and drain tubes are threaded into the crankcase and then the sump body is soldered to them with low-temp solder. This step permanently connects the sump to the crankcase. The threads were sealed with thread locker before soldering.
In my limited experience with soldering I have learned to use activated rosin flux with my soft solders and to design my parts so the solder can inserted between the pieces before heat is applied. I try to never hand feed the solder as this usually ends up needing lots of post clean-up. Even so, because I didn't have any small gage high temp solder I got some unwanted wicking when I soldered the bung onto the sump body. I ended up spending an hour under a microscope with a tiny needle file cleaning this up and blending the fillet around the saddle area. The drain and scavenger tubes didn't need any clean up after being soldered to the sump body with low-temp solder. The last photo shows all the components of the completed oil system installed into the rear crankcase section. I plan to start working next on the cam ring assembly for the front cylinder bank. This shouldn't require much new design work as it will be nearly identical to the one used in my 9 cylinder. - Terry

 

[mayhugh1]

For the remaining internal parts I plan to start under the front cover and work my way toward the distributors at the rear of the engine. I'll leave the master/slave rods to the end as they'll just be in the way as I test each completed subassembly driven by the crankshaft.
My first step is to machine the cam disk(s). The front one should be straightforward as it's identical to the one in my 9 cylinder. I'll machine the front and rear cam disks at the same time since the setups will be identical. I had to re-make the fixture I used to mill the cam profiles for my 9 cylinder since it seems to have already been re-appropriated for another project. The intake and exhaust lobes are machined on their own separate rings on the cam disk. I'm using the "Patterson" cam profile that was recommended for my 9 cylinder. Basically, it is an equal acceleration/deceleration ramp profile with symmetrical lobes equally spaced around the perimeter. The separation between exhaust and intake lobes is 216 (crank) degrees while the intake/exhaust durations measured at .006" valve lift are 208/248 degrees, respectively. The only difference between the front and rear cam disks is that the exhaust lobes are on the top ring of the front cam, while they are on the bottom ring of the rear cam. The cam for the front row of cylinders rotates in a direction opposite to the cam for the rear row of cylinders, and both are geared to rotate at 1/8 the speed of the crankshaft.
The cam disks begin life as slices of 4140 thick-wall tubing that I salvaged from a scrapped oilfield pressure vessel. I annealed the drop and then sliced off two 1/2" thick disks. The disks were chucked into a lathe and the bearing faces were machined. These faces were polished as they will ride against surfaces that were machined into the front and rear bronze bearings. The centers are then bored out to later accept a ring gear. The parts were flipped around in the lathe chuck and a second bearing surface was machined on each disk. Delrin retainers will bear against these surfaces to hold the cam disks in place as they are driven by jackshafts which, in turn, are driven by integral gears machined into the crankshaft.
A fixture holds the disks in place in the mill vise while the cam profiles are milled into the rings. The rings, themselves, are only .093" wide and .060" apart. I created full models of both the front and rear cam disks in SolidWorks in order to keep my own confusion to a minimum. I generated the lobe profiles by manually entering the lobe heights for each degree of rotation. Four g-code programs were generated so the profiles could be milled on both sides of each disk. In order to maintain the workpiece reference when the disks were flipped over, a tiny hole was drilled through each disk and into the fixture at the 0 degree position before the first profile was run. When the disk was flipped over for the second profile, a pin was inserted into the cam disk and into the fixture to maintain the 0 degree location. A shallow oil groove was machined across the bearing surfaces that mate with the bronze bearings.
While machining the front cam profile I stumbled across the same bug in my CAM software that I ran into more than a year ago when I machined the cam profile for my 9 cylinder. I eventually found a work-around, but the 9 cylinder cam was gouged slightly and had to be re-made from scratch. When I saw the exact same gouge on my new front cam I couldn't believe that I had forgotten about my work-around. Now I have two identically spoiled parts in my scrap box.
After machining, the disks were heat treated to restore the hardness of the 4140. I sealed the disks in stainless foil wraps filled with argon to eliminate scaling. They were then heated to 1550F for one hour, quenched in oil, and then tempered at 500F. The Rockwell hardness should be somewhere around 50. After heat treating, the bearing surfaces were cleaned up a thousandth or so on a surface grinder and the bearing surfaces were re-polished. The open ring design evidently helps to reduce warpage during the quench as I was expecting the part to twist several thousandths.
The cam disks were finished by pressing in the ring gears which drive them. A commercial internal gear was purchased, modified, and lightly pressed into the center of the cam disk. Loctite bearing retainer was used to maintain the assembly. -Terry

 

[rcfreak177]

I'm loving this build as I did with the 9 cyl radial.

The stainless steel bag and argon method is a great idea to avoid carbon scaling, might have to try it some time. Thanks for the tip.

keep up the great work, I have found this build very detailed and have learnt lots of little tips and tricks. Much appreciated.

Baz.

 

[mayhugh1]

The cam retainer and some hole additions to the front main bearing will finish off the internals of the engine under the front cover. The cam retainer supports a jackshaft which connects the cam to the crankshaft. The integral gear that was cut into the front crankshaft meshes with the top gear on the jackshaft. The bottom gear on that shaft engages the ring gear now integral to the cam. The result is that when the crankshaft spins, the cam is driven at 1/8 speed in the opposite direction. The retainer also keeps the bearing surface of the cam disk against it's mating surface on the front main bearing.
An important requirement of the retainer comes into play during final assembly when the relative positions of the crankshaft and cam are being adjusted to synchronize the valve timing to the position of the piston in the cylinder. In order to do this the jackshaft has to be pulled forward to disengage the ring gear without disturbing the position of the crankshaft in order for the cam to be rotated. Done by trial and error, this is repeated as necessary until measurements show an optimum compromise position is found. This means the retainer plate will need to come off the main front bearing several times. On the front crankshaft there is an integral shoulder which bears against the inner race of the ball bearing in the front cover to set the thrust clearance for the front crankshaft section. The position of this collar on the crankshaft is, by design, sufficiently forward to clear the top gear on the jackshaft when the jackshaft bottom gear is disengaged from the cam ring gear. The inside contour of the front cover was designed to accommodate the position of this shoulder as well as the retainer plate, itself. In my 9 cylinder there was a similar retainer. Three spacers secured it to the front main bearing. Because of the close meshing of the two sets of gears and the precision fit of the jackshaft to its bearings, these spacers could not be interchanged without creating a bind. Rather than open up the bearing or gear clearances, I uniquely marked each spacer so they could be returned to their proper locations during assembly/disassembly. In this engine I'm machining these spacers integral to the retainer plate to eliminate this problem and to simplify the timing adjustment a bit. I've been thinking ahead about the rear cam and, as will be seen later, integral spacers will definitely be helpful back there.
The retainer starts out as a 1" thick block of aluminum with a bearing bronze slug Loctited and pressed into it. This slug will become the bearing for the top end of the jackshaft. Three arms are machined at the outer periphery of the retainer. These arms will hold Delrin bumpers to keep the cam disk from moving more than a 3-4 thousandths away from the main bearing. The integral spacers set the height of the retainer plate from the main bearing. This height, in turn, sets the jackshaft thrust clearance to about .010". Nearly all the machining for the retainer was done from the same side of the workpiece so it was simply held in the mill vise. All features were roughed and finished in two separate operations before drilling the holes. The retainer was then flipped over and the counterbores for the SHCS mounting bolts were bored. This allowed me to mount the semi-finished retainer to the front main bearing for final machining.
The front main bearing was mounted to its original machining fixture on the mill, and then the retainer mounting holes were drilled and tapped. The retainer was then attached to the bearing with its mounting screws, and the retainer plate was faced to its final thicknesses. The hole for the jackshaft was then drilled and reamed through both the retainer and main bearing. Delrin bumpers were turned and pressed into the three flat bottom holes at the outer arms of the retainer. Their lengths were adjusted for a .004" clearance to the top surface of the cam disk.
The jackshaft, itself, was turned from 303 stainless. I noticed from the Chaos Industries photos that they milled small oil grooves into the jackshaft to promote oiling in the close-fitting bearing at either end of the shaft. This was not a feature in my 9 cylinder plan set but sounds like a really good idea, and so I included it here. The gears were sliced from left-over stock that I had machined for my 9 cylinder. They were pressed/Loctited into position on the shaft and then pinned with 1/16" dowel pins. The final result was that the cam turns freely with no hint of drag or bind when the crankshaft is manually spun in the front crankcase assembly. The next step is to tackle the much more challenging retainer for the rear row of cylinders. - Terry

 

[ozzie46]

Your doing amazing stuff here. Thanks for sharing.

Ron

 

[John Rus]

Fabulous work there mate. :bow::bow::bow:

Everytime I look at this thread it keeps raising the bar higher and higher on my V16! If it wasn't for people like you I would probably never design or build a engine half so nice!

Regards,
John.

 

[don-tucker]

This is indeed wonderful work,makes my steam engines seem like toy town,I usually turn my nose up at ic engines and Cnc but you have made me sit up and take notice,an inspiration
Thank you
Don

 

[petertha]

2 questions Terry

Re the 4140 cam disc, you mentioned sourcing from oilfield pressure vessel, annealed, sliced, machined, then heat treated @1550F, oil quenched, temper @ 500F 'to restore the hardness of 4140'.
- was the first stage (annealing) because it was originally in some other hardness state from its oilfield purpose?
- ie if you happen to have stock 4140, would it be just slice/machine, then harden?
- out of interest, does this exceed what Hodgson plans call for? Ive seen so many ways of going about this on model engines ranging from nothing to case harden to what looks like cadillac here

Re the bronze bushing slug technique again, what is your recipie in terms of OD/ID fit & locktite PN? Any recipie difference between aluminum vs steel as the parent metal? Ive always been scratching my head how thin wall bushings could be pressed into connecting rods & such without distorting, but I now I know better - a better technique with a slug.

 

[mayhugh1]

2 questions Terry

Re the 4140 cam disc, you mentioned sourcing from oilfield pressure vessel, annealed, sliced, machined, then heat treated @1550F, oil quenched, temper @ 500F 'to restore the hardness of 4140'.
- was the first stage (annealing) because it was originally in some other hardness state from its oilfield purpose?
- ie if you happen to have stock 4140, would it be just slice/machine, then harden?
- out of interest, does this exceed what Hodgson plans call for? Ive seen so many ways of going about this on model engines ranging from nothing to case harden to what looks like cadillac here

Re the bronze bushing slug technique again, what is your recipie in terms of OD/ID fit & locktite PN? Any recipie difference between aluminum vs steel as the parent metal? Ive always been scratching my head how thin wall bushings could be pressed into connecting rods & such without distorting, but I now I know better - a better technique with a slug.

Hi Peter,
The 4140 that I had was originally hardened for use as a high pressure cryostat. I was given a piece of that had been sawed off with an abrasive chop saw when the vessel was scrapped. I had to anneal it in my shop so I could work with it. When you purchase a length of 4140 from a metal supplier, it is most likely already in an annealed state.
My 9 cylinder plan set called for hardening the cam rings to about R45 but did not specify anything about hardening the lifters. This would put all the wear on the lifters. Since there is only a small point of contact between the two in my version of the engine, especially since I was machining true hemispherical ends on the lifters, I decided to harden the cam on my 9 cylinder to about R45 and then hardened the lifters to about R50. I decided to reverse it on this engine to put the wear back on the lifters instead of the cam. So I went to R50 on the cam and plan R45 for the lifters.
With respect to my "press fits" and "slip fits", I have to admit I throw the terms around carelessly. In my shop there is no more difficult measurement to make than one involving the i.d. of one part and the o.d. of another when dealing with diameters are greater than the limited pin gage set that I own and when a few tenths makes a difference. I like my slug bushing technique because I can be off several tenths to the tight side and then just use more pressing force without worrying about distorting something. I always use Loctite high temp bearing retainer for good measure just I case during the pressing operation I find out the hole was bigger that I thought. But it doesn't come without its own problems. If the hole is equal to or less than the diameter of the part you are pressing in and if the surfaces are finished properly and clean, the Loctite will start to set immediately from the heat generated by the pressing operation and so you have to be prepared to finish the pressing operation right now or the part will be stuck half way with no hope of recovery.
With something as precious as my cam disk assembly with a large number of hours invested in the cam and a $95 commercial ring gear I made sure I had what I called a slip fit. Qualitatively, what this meant was that I could snap the two parts together with my fingers. In fact, I practiced a few times before adding the Loctite. I was also standing beside my press with and ready to use it if things started going wrong. In this particular case there is so much surface area between the two parts that the Loctite will provide the same holding that a very tight press fit would provide without any of the distortion. I did some experiments several years ago with with this bearing retainer using different classes of fits and seeing just what it takes to bond and unbound two parts together and became a big believer in it. Another thing I've learned is how to tell if you achieved the perfect slip fit with respect to surface finish and cleanliness. The parts will set up up within a few few seconds - not to full strength, but enough that you can tell - within 5 to 10 seconds. If they don't, I put them in my welding rod oven (about 100F) for a few hours to kick off the cure. - Terry

 

[petertha]

Real good info, thanks. Your material usage caught my eye because I have a feeling there may be similar resources of suitable metal cut-offs via scrap/salvage shops in my (oily) neck of the woods. I'm not in that line of work per se but I have seen 4140 for example as being pretty common. But real important point noted - all depends on where it originated from &any previous heat treatment.

So what Locktite flavour would you typically use for bronze slug inside aluminum parent material & same question if steel parent? How about primers or whatever they call prep agents for certain Locktite PN's?

 

[mayhugh1]

Real good info, thanks. Your material usage caught my eye because I have a feeling there may be similar resources of suitable metal cut-offs via scrap/salvage shops in my (oily) neck of the woods. I'm not in that line of work per se but I have seen 4140 for example as being pretty common. But real important point noted - all depends on where it originated from &any previous heat treatment.

So what Locktite flavour would you typically use for bronze slug inside aluminum parent material & same question if steel parent? How about primers or whatever they call prep agents for certain Locktite PN's?

Peter,
I use Loctite 609 if I have less than .0005" (radius, not diameter) gap and I use 620 if the gap is between .0005" and .0015". If it is more than .00015" I consider re-doing the part depending on the application and my cost in time or dollars. I use the same retainers regardless of the metals I'm joining. I don't use any primers but I finish the part's surfaces as though I were putting a shaft through a bearing. I clean and dry the parts with acetone before applying the adhesive. I'm also careful to clean the adhesive off any outside surfaces especially if the parts are going inside my rod oven for curing. Any adhesive left on an open air surface will cure to a very hard and difficult to remove crust when heated. Without heat, you can usually clean off the surfaces even after a 24 hour cure. - Terry