Author Topic: Modified Kimble engine (Read 7026 times)

wdeputy · « **on:** August 03, 2014, 08:06:24 PM »

Disclaimer: This is not a complete build log. The engine has been finished and the photos do not show every step or piece. It gives a general idea of how things were made.
I found the plans for this engine on John-Tom a while back and felt it just needed to be built. As drawn, it is a rather square-ish thing so I decided to make it more like a model of a real engine. It is all bar stock but hopefully some of it looks like castings as that was the intent.
I started by making the body of the engine. The plans call for it to be 3/8" thick but I felt making it 1/2" would give better proportion. A piece of aluminum was laid out and chain drilled for cutting the outside. This was then turned upside down on the brass top piece and the holes drilled for the screws that would hold the two pieces together. This was done to have the screws from the bottom rather than the top as shown in the plans.

wdeputy · « **Reply #1 on:** August 03, 2014, 09:55:11 PM »

While drilling the aluminum body, a 1/8" hole was made at the location of the vane pivot. This undersized hole would later be used to locate the side plates. The screw holes were tapped into the brass top piece for 3-48 thread. The aluminum was counter-bored for SHCS.
Next step was the body to hold the valve. Original plans did not have any means for exhaust other than the two 1/16" holes. My plan was to make a body to hold the valve and position it higher in order to add exhaust plumbing. Since the side pates would not cover the valve, a different tact was devised. Brass rod was turned to 5/8 diameter. This would allow for a rear cover. The remainder of the body was turned to 1/2" with a small nose for the valve shaft to exit. The body was then cross drilled and reamed to accept a rod that would become the exhaust ports. The center of the hole was 1/16" from the center of the valve body, per the plans. A 1/4" hole was drilled at 90 degrees to the first hole. This would become the inlet port. The back of the valve was parted off and an additional small piece pated to make the rear cover. This made the cover exactly the same size as the body. When all the lathe work was done a piece of brass rod was silver soldered into the exhaust holes.

wdeputy · « **Reply #2 on:** August 11, 2014, 02:02:22 AM »

The lower, aluminum, part of the body was cut out and the sides milled. The upper and lower parts were bolted together and milled on the sides followed by flycutting both faces. This made for an exact fit of the two pieces. Using the hole for the vane shaft as a center, the slot was drilled and cut for the valve body. I used a dial height gage to check the location of the hole, thinking this would be needed later. The top part of the body was then marked for the radius that had to be cut. This will be the top sealing area for the vane.

wdeputy · « **Reply #3 on:** August 11, 2014, 02:13:53 AM »

The upper portion of the brass was cut away and a hole was cross drilled to fit the exhaust outlets. The piece was then put in the rotary table and mush waste was removed to produce the curved outer edge. The hole for the vane pivot was again used as a center for this operation. The rotary was then put in a vertical position without moving the body. A round end mill was used to make a groove in the outside edge. A curved piece of tubing will later be put in this groove to be the air passage. when both sides were done, the RT was again placed horizontal and the lower part of the body was removed. An end mill was used to make the radius for the top of the vane. A 1/16" hole was drilled on each end of the radius to connect with the air passage.

wdeputy · « **Reply #4 on:** August 11, 2014, 02:38:04 AM »

The brass piece was filed to give it more of a "casting" appearance and then the valve body was attached. The exhaust tubes had been silver soldered and a lower temperature solder was used to prevent the joints from loosening. The solder was flattened and curved to fit the slot in the top of the brass piece. Flux was applied and the body put in place. A length of wire coat hanger, bent to shape and with a weight taped to it, was used to hold the body. This wire was placed in the 1/4" hole drilled for the air inlet connection. All was heated with a propane torch and when the solder flowed the body could be seen to settle in place. The inlet hole was just large enough to allow drilling the two air passages required. These were drilled to depth and then cross holes were drilled to connect with the milled grooves. A piece of 1/4" brass for the inlet was then soldered in place. A simple jig was formed from aluminum to hold the assembly while the valve body was drill and reamed to final size. Two small pieces of annealed brass were then bent to fit in the grooves with caps that were turned on the lathe to fit in the end of the tubes. These were drilled to match the holes in the main brass piece before installation. Drilling after being soldered in place could well leave chips inside that could not be removed. The tubes were soldered using low temp soft solder.

tvoght · « **Reply #5 on:** August 11, 2014, 02:46:30 AM »

It's great to see details on the build of this interesting engine. I'm watching!

--Tim

fumopuc · « **Reply #6 on:** August 11, 2014, 05:47:45 AM »

I am also following along. Seems to be a very interesting build.

smfr · « **Reply #7 on:** August 15, 2014, 12:35:49 AM »

Me too, this looks great so far!

Simon

b.lindsey · « **Reply #8 on:** August 15, 2014, 12:59:42 AM »

Nice write up and pictures too. I'm along for the ride also.

Bill

wdeputy · « **Reply #9 on:** August 17, 2014, 02:55:52 AM »

Thanks for the comments!
Continuing now with our story-
The original plans do not call for any form of bushing to support the vane shaft. I wanted something more than just the cover for support and the "back" side should be sealed as well. I drilled a piece of brass rod to 1/8" to match the hole in the main body. A dial indicator was used to measure the depth of the hole for the back bushing. A shoulder was cut to match the thickness of the cover plates. A taper was made and the piece parted off. The cover plates were drilled and the bushings soldered in place. The sides were then cut using a slitting saw. To determine the cut line, each side was placed on the body and a scribe line made. A parallel line was then made to reduce the width by about 1/16". A chunk of drill rod (silver steel) was used in the valve shaft hole and the bushings to maintain alignment while scribing. The sides then made their way to the rotary table to create the curved top.

wdeputy · « **Reply #10 on:** August 17, 2014, 03:01:30 AM »

With the side plates made to size it was again back to the rotary table to drill the screw holes. The original plan was to have studs on each side but it ended up being through holes with a single stud extending from one side to the other in each hole.
Many thanks have to be given to the shop cat for his advise and encouragement during this build.

wdeputy · « **Reply #11 on:** August 17, 2014, 03:32:03 AM »

Making the valve was not anything special. It was turned from 12L14 steel and the slots and hole completed using a spin index. The only difference from the plans was the length due to the longer body.
One of the biggest issues with this engine is trying to seal the vane or "piston". The original plans call for a rectangular seal to be made of brass and fitted to the end of the vane in a groove. This seal would be held against the top of the body by a tiny wire spring. The side would seal by means of a very close fit. This seemed to allow too much chance of scoring on the sides and many headaches getting the fit.
The vane was made of 3/16" brass with a 1/16" flat bottom groove on three sides. A 3/16" diameter round groove was made on one end of the vane using an end mill to fit on the shaft. A hole was drilled in this end to pin the vane to the shaft. (The plans call for a tongue and groove fit and the dimensions given are wrong.) The vane was pinned to the shaft and soldered in place.
I decided to try making a seal of delrin. The idea was to have a square top seal that would just fit the body and thus seal all the sides. The delrin rod was milled to fit the groove using the spin index. I don't have photos of the next step (maybe that's better). The flat tongue of delrin was held to a piece of aluminum using carpet tape. The inner edge was then milled away to create the sides of the seal. This was then cut off with an allowance to have a flat spring at the top of the vane. The body had to be very smooth to make the seal airtight.

wdeputy · « **Reply #12 on:** August 17, 2014, 03:40:44 AM »

I'll save the suspense and jump ahead a little - the delrin seal didn't work. I had a plan "B", however. I had a length of 1/16" nylon rod that was cut to make side seals and a separate top seal. A small piece of brass shim stock was used to make the spring. This seemed to fit well and moved with little friction.
Before getting to the seal issues the sides were bolted in place and the bushings and lower body were drilled and reamed to fit the vane shaft. I used a 3/16" shaft as apposed to the 1/4" shaft of the plans. Sorry for not making that clear earlier.

wdeputy · « **Reply #13 on:** August 17, 2014, 03:55:45 AM »

The flywheel is a combination of an aluminum rim and steel components. I used a hole saw (!!) to cut the rim from a blank of 3". The inside was then finished and spoke holes drilled using the RT. The hub was made of 12L14 steel and finished in the spin index with some decorative grooves and the spoke holes. Spokes were cut from drill rod and the whole lot was held together with hose clamps for soldering. After the hub was silver soldered, a bit of super glue was applied to the joints of the spokes and rim. The flywheel was then finished to size.

wdeputy · « **Reply #14 on:** August 25, 2014, 04:32:35 AM »

The original plans call for the eccentric to be fastened to the flywheel. I wanted it next to the crank disk on the outside of the crank support column. I also decided that the eccentric strap should be split and ride in a groove on the eccentric. The hub of the strap was laid out on a piece of brass and the center drilled for a reference point. This was then bolted to a scrap hunk of aluminum and mounted to the rotary table. A small clamp was made to hold the end where the strap would emerge. The piece was then cut to OD size. A small round groove was made on each side, parallel to the strap. Brass tubing was soldered into the grooves and the entire hub was cut across the center. This cut went through the two tubes. Both halves were then bolted together again and the center of the hub was bored to size. The projection for the strap was filed to shape and the strap (round rod) was soldered in place. The eccentric hub was made of steel with the throw to match the plans.

wdeputy · « **Reply #15 on:** August 25, 2014, 04:52:13 AM »

The eccentric noted above was designed as a flat strap on the original plans. The connecting rod was made likewise. They were bent to align with the valve arm and vane arm and had pins on the ends for the pivots. Placing the eccentric outside the support and in line with the valve arm meant that the connecting rod would be moved further away as well. My idea was to offset the end of the rod at the vane arm. The main portion of the rod was cut to length and a small piece soldered to one end. This would form the offset fork at the arm end. Both pivot holes were drilled and reamed to size. The fork was formed in the mill after narrowing the rod slightly. I left the crank end of the rod at the original size of the brass for appearance sake. This just shows in one of the photos. A groove was made in the outside face of the rod, again for appearance. The bearings were made of brass, squared with the spin index and slotted to fit the columns. They were drilled slightly undersized to be reamed at installation. They were parted off and set aside.

wdeputy · « **Reply #16 on:** August 25, 2014, 04:57:57 AM »

The columns were squared and then the slots were cut for the bearings. While they were clamped together, the holes for the retainers were drilled and tapped. Excess material was removed at the band saw and both columns were mounted in the rotary table. The large radius was then cut and the edges trued. Both pieces were kept together for all operations to keep them the same.

wdeputy · « **Reply #17 on:** August 25, 2014, 05:10:04 AM »

The base was laid out and drilled for all the mounting holes. When the columns were bolted in place the crank bearings were reamed. I used adjustable parallels to support the columns while reaming. Several small fasteners needed to be made for the crank and eccentric pivots.
OK, gotta fess up here. My plan "B" of using nylon rods to seal the vane proved to be just as worse as the original plan. When I got to this point and made a trial assembly, it leaked way too much. Plan "C" was to try using carbon coated string. A larger piece was unwound and the separated parts were just the right size to fit the grooves in the vane. This worked just like I had planned from the start. The string formed nice tight corners and did not increase the friction against the sides. I don't know how they sealed the prototype but it must have been a real pain.
The photo below is the top of the body at trial assembly and shows the solder joints before painting. Then there is the completed engine.

Jo · « **Reply #18 on:** August 25, 2014, 07:20:34 AM »

I do like you engine... I had to go and download the plans from John-Tom's site only to find they are in the Elmer's engine book

Those little curvy modifications you have done to the original "square" design does make it look so much nicer

Jo

Saxalby · « **Reply #19 on:** August 25, 2014, 11:07:33 AM »

Nice engine.
Have looked on the John-Tom site for the plans but cant seem to find them.
Can anyone give a direct link to the plans.

Regards
Barry

Saxalby · « **Reply #20 on:** August 25, 2014, 04:58:23 PM »

Found the plans

wdeputy · « **Reply #21 on:** August 26, 2014, 07:44:25 AM »

Thanks for the comments. With any luck this has given someone an idea for their own projects.
Walt

Saxalby · « **Reply #22 on:** August 26, 2014, 11:49:24 AM »

Certainly has. Just starting to sort out various raw materials to make a start.

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Author Topic: Modified Kimble engine (Read 7026 times)