Miniature Tunnel Ram on Demon V8

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
In the video it appears you are revving it up by adjusting voltage? ?
I have a question on this also

Thank you for noting that. Yes I am revving the engine with a voltage supply. It will start and run okay on a 6V battery, but lacks crisp throttle response. I want to remedy that, and have several theories and solutions. I am hoping to hear your and/or other expert's input.

The distributor has a 8 hole aluminum disc with 8 rare earth magnets equally spaced at the circumference passing over a hall sensor affixed to the body of the distributor housing. The signal triggers a Jerry Howell TIM-6 circuit board that I soldered together from a kit.

Full disclosure: I am a slow learner at all things electronic.

In troubleshooting this issue, I attempted to run on a 6V 7AH lead acid battery which it starts and runs happily on up to about 3200 RPM. It stumbles after that no matter where I rotate or time the distributor to. The 6V ATV coil was purchased from the Howell site also.
I tried running it off my 12V lawn tractor battery and promptly smoked one or both transistors. The diode and resisters were fine. Replaced the components and it worked again the same way.

My guess is that I do not have the magnet disc phased correctly with the rotor, so I am contemplating refabricating or modifying the distributor housing to allow adjustment. I like the rule: "If you can't make it right, make it adjustable"😒

I contemplated making another rotor and affixing the brass strip again precisely following Steve's instructions in the plans. I overthought this step during the build because of perceived backlash in my homemade bevel gears on the cam to distributer shaft.

It could also be a carburetor issue, but I feel that the variable voltage improving the throttle response is a clue. By increasing the electrical potential, it may be bridging the out of phase rotor tip to wire contacts? They all appear to be clean except for the coil one which blackens up after running several times.

Perhaps a spring brass part or graphite brush could be made small enough to fit here also.....

Any thoughts would be extremely welcome.
Russ
 

Attachments

  • 20210925_165234.jpg
    20210925_165234.jpg
    2.2 MB · Views: 0
Last edited:

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello,
The next parts to be made were the cylinder heads. A rigid and adjustable means of supporting these parts in the various angles was needed, so an aluminum table was made based on a terrific video by Mr. Pragmatic Lee on YouTube.

The pivot is 2" round aluminum and may be clamped in the mill vise for light duty, or clamped to the table slots as shown. It is easy to make and fairly repeatable if one sweeps the parallels with an indicator. It also proved useful later for the intake.
 

Attachments

  • 20210822_105344.jpg
    20210822_105344.jpg
    3.2 MB · Views: 0
  • 20210822_180348.jpg
    20210822_180348.jpg
    3 MB · Views: 0
  • 20210904_180228.jpg
    20210904_180228.jpg
    7.7 MB · Views: 0
  • 20220103_090614.jpg
    20220103_090614.jpg
    3 MB · Views: 0

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello again,
The next few weekends were pretty tedious as I had anticipated making valvetrain parts. I opted to wind my own springs using an online calculator here:
Valve material was SS 303, and machined it 0.100 at a time while pulling out of a collet chuck. Followed up by using a shop made external lap to final tolerance.
Rocker Stud.jpg
Valve Spring Retainers.jpg
Valve Springs.jpg
Valves.jpg
 

Attachments

  • Rocker Stud.jpg
    Rocker Stud.jpg
    1.5 MB · Views: 0
  • Valve Spring Retainers.jpg
    Valve Spring Retainers.jpg
    1.4 MB · Views: 0
  • Valve Springs.jpg
    Valve Springs.jpg
    1.5 MB · Views: 0
  • Valves.jpg
    Valves.jpg
    1.2 MB · Views: 0

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello,
The camshaft was made on a 7x14 lathe using a jig and dial that was in the plans. A cutting chart gave depth of cut based on relative indexing of the camshaft blank. A standard grooving tool with carbide tip was long enough to use. I used Dykem to mark the lobes at each step and followed the chart 5 degrees each step. Only a little bit of filing and emery cloth at the end gave very satisfactory results. I had never made a billet cam before and thought this was a brilliant idea by Steve.
Russ
20210906_172001.jpg
20210912_120257.jpg
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello again,
I wanted to move on to fabricating the crankshaft, but didn't have the stress-proof material on hand. I started the distributer and made a plug cutting tool for the plug towers. I made four attempts using black Delrin, Bakelite, Micarta and finally some Teflon looking white plastic. The Delrin was glued up to achieve the thickness and fell apart. The Bakelite machined great, but the towers fractured when pressing the brass contacts in. The Micarta was too tough and dulled my tooling. The white plastic ended up being the best. I didn't have the resources to order black Teflon, so I painted it. Later on I removed the paint, as it chipped off in places.
bakelite cap.jpg
teflon cap.jpg
20210925_165234.jpg
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello,
The project veered down a rabbit hole when it came to gears. I personally enjoy tool making as much as making the project, and decided to make all the gears for this engine rather than purchase them. I have used simple shop-made gear hobs on the rotary table, but the tooth profile seemed too sharp in my opinion and cumulative error when indexing multiple passes is probably why on my sketchy rotary table and mill. Ivan Law authored a terrific book that is still in print here for less than $15. It provides several options on different techniques to be successful.
https://www.amazon.com/Gears-Gear-C...93-9118-2cfb6c6a10dc&pd_rd_i=0852429118&psc=1
I chose the eccentric disc type, and needed 4 cutters for the different gears due to number of teeth. Only thing I had to purchase was a flat of O-1 tool steel, which I also used to make a replacement wood plane blade.
O-1 plate.jpg

One starts by making button cutters for each size disc. I made double ended ones to economize the setups and material. Also made a wooden box, which required a table sled for the box joints, and a hinge jig for making brass hinges. See where this is going....?
button tool.jpg
machining discs.jpg

Anyway, the gear tooling cost far less than commercial sets if one doesn't put a price on labor which I don't.

4 button tools.jpg

heat treated disc 1_4.jpg
boxed 48 dp set.jpg
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello,

All gearing was machined using brass blanks. The spur gears only need a single pass of the cutter at fairly low speed (300 RPM). Bevel gears need 3 passes; indexing the blank differently for each pass creating the triangular tooth profile. Ivan Law provides excellent instruction in a chapter just for bevel gears. I set up the camshaft in the mill vice and used the fine adjustment on the quill to determine the height of the distributor shim. I ended up cross drilling the bevel gear to distributer shaft with a hardened pin later on, as the tiny #2 grub screw would loosen when running the engine. This makes distributer disassembly more difficult because one cannot access the rotor to shaft set screw.

Another thing I did differently was to use an old morse taper dead center and attach it to a chuck backing plate that accepted my 4 jaw chuck. The thought was that I would turn the blank in the lathe, remove the chuck/taper and reinstall in the rotary table. This should eliminate some concentricity error, and allow swapping back to the lathe to debur the teeth. Looked good on paper, but in reality I think that the amount of stick out from both the headstock and table increased deflection. In the end, it's a compromise. Probably need to replace the spindle bearings in my little lathe. One might be able to see some error in depth of cut on the larger cam gear in picture 4.
cam idler gears.jpg
cam gear.jpg
bevel gear.jpg
gear train.jpg

Russ
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello,
Thank you all for the interest and likes. The multi-plane crankshaft was a first attempt for me. I had completed several flat plane crankshafts using the fabricated method on steam, hot air and four cylinder IC engines. I researched a lot and used the approach documented by the Black Widow V8 creators documented in Model Engine Builder Issue #30.
First off the crank sleeves were made to support the OD as journal material was removed. I used scrap 1" sch 80 carbon steel seamless pipe.
Crankshaft Sleeve.jpg

A special parting tool bit was made by carefully grinding a HSS blank. A Deckel tool grinder would be nice for this, but I made do with the grinder and dremel. This reduces chatter significantly.
Bifurcated Parting Tool.jpg


Also note the drive fixture that is in the four jaw chuck. It has two centers that fit the center drilled holes in the crankshaft ends to repeatedly remove and reinstall the blank so one can remove material in the mill, change position of support sleeves and swap ends. I set travel stops to reduce the possibility of a crash.
Milling Journals.jpg

The machined flats near the ends are just there to properly index the crankshaft blank, so I can center drill the ends. I lack the Z height on my mill, and had to rig up something in the drill press.
Finished crankshaft.jpg

The finished crank came out nice. There was some ovality on the rod journals that had to be fine tuned and resulted in varied dimensions of the finished OD. This was compensated by making matched rod bearings for each journal. The crankshaft took me nearly 5 days to complete, so I didn't risk getting fancy with shaping the counterweights.

Question for the group: Does anyone have an idea of how many Demon V8s have been successfully completed?

Russ
 

petertha

Well-Known Member
HMEM Supporting Member
Joined
Jun 24, 2010
Messages
1,991
Reaction score
628
Very interesting. So the crank sleeve fixture is intended to be clamped either side of the journal being cut to keep the others aligned? Is this an alternative to other methods I see where spacer blocks are temporarily attached in between the webs as the turning progresses. What material is the crankshaft?
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
What material is the crankshaft?

Thank you for the questions!
Plans called for stress relieved 1144 carbon steel to minimize distortion. I purchased a 12" long round bar at Online metals for approximately $12 at the time. The magazine article called for 4340 steel which is stronger, but that engine had forced oiling so their crankshaft was cross drilled for oil passages. The more common 1144 worked great for me.

Is this an alternative to other methods I see where spacer blocks are temporarily attached in between the webs as the turning progresses.

This method of clamping is intended to minimize deflection when turning the off center planes between centers. The limitation of course is the counterweights must be round.

Very interesting. So the crank sleeve fixture is intended to be clamped either side of the journal being cut to keep the others aligned?

Yes. One must make several length pieces. I started at the centers and worked outwards

I would like to share the full article, but I believe it is copyrighted/protected.
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Hello again,
Production parts next are pistons, rods, rings and rod bearings. The rods were made entirely on a rotary table to achieve the taper and radius on small end. They have small tabs intended to scoop up oil with a small passage through the bearing as this is a splash oiling system. I later discovered that too high of an oil level in the pan will flood the cylinder walls resulting in smoke. They are all identical, but stamped them due to bearing sizes and future differences in wear after disassembly.
connecting rod.jpg


Pistons were sized, grooved and counterbored on lathe, then parted off moved to mill for small end pocket. Back to lathe to face the top, and then back to mill to drill and ream the wrist pin holes. Made a fixture that fit the pocket to index the wrist pin hole based on other peoples advice.
piston.jpg

wrist pin.jpg

Next I soft soldered two pieces of bronze bearing material and using a four jaw chuck in the lathe, made individual bearings for each rod. The journal size was fairly consistent, but the side thicknesses varied. I made them oversized widths and carefully fit them by using wet/dry abrasive on a surface plate.

split bronze bearing.jpg


The piston rings were made using gray cast iron and the method recommended on the plans. I machined them, split them, filed ends and sanded to thickness on the surface table. The piston grooves are supposed to be 0.020 inch and was made using an exacto blade carefully clamped in a shopmade tool holder. Very very little stickout. Measuring the groove width with a feeler gauge showed that the grooves were undersized 0.001 to 0.002 so the rings ended up being tighter than they should be and not sealing correctly. I made lots of spares and that helped later on.
rings.jpg

After the first few runs, I disassembled the engine and evaluated the rings and cylinders (also the valves and seats) and re honed the block and replaced rings that had cracked (2) and were sticking (3). The compression was tested using a brake bleeder type vacuum pump
evaluation.jpg
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
879
Reaction score
136
Location
Minnesota
ive made tools out of band saw blades bu not exactly , I’ll have to temper that one .
Thank you for the questions!
Plans called for stress relieved 1144 carbon steel to minimize distortion. I purchased a 12" long round bar at Online metals for approximately $12 at the time. The magazine article called for 4340 steel which is stronger, but that engine had forced oiling so their crankshaft was cross drilled for oil passages. The more common 1144 worked great for me.



This method of clamping is intended to minimize deflection when turning the off center planes between centers. The limitation of course is the counterweights must be round.



Yes. One must make several length pieces. I started at the centers and worked outwards

I would like to share the full article, but I believe it is copyrighted/protected.
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
I wanted to attempt something different for the intake. Really liked the idea of a supercharger such as Steve has plans for, but after studying his build log decided it was outside my skill level making the lobes functional. I learned of a process called lost foam casting on Youtube University, and set my hopes on a tunnel ram with dual carburetors.
A youtuber named Kelly has a site here:
Kelly has a lot of informative videos where he replicates TransAm racing parts for 60s-70s Ford engines.

First I built a hot wire cutting table to control dimensions. The concept is to use a transformer and dimmer switch to control low voltage current thru Nichrome wire held in tension. I have been successful replicating thin sections of 0.100 this way to use as a valley pan for the intake.
hot wire cutting table.jpg

Then I had lot's of fun mocking up several prototypes to get the proportions just right.
prototypes.jpg

The foam is high density foam board used to insulate block walls here in Florida. It is glued up with low temperature glue sticks, and filleted using plumbers toilet bowl wax. I had two good ones that I then dipped in a thinned drywall mud mixture cut with dishsoap. The soap makes the foam and wax less hydrophobic. The plaster mix keeps sand out of the casting and improves surface finish. The pattern is placed in regular sifted sand (no clay) and shaken using a sawzall. The first pour is shown below, and one can see that my pouring basin floated and ended with a molten puddle of aluminum on top of the sand instead in the pattern
first pour.jpg

failure.jpg

I had anticipated several attempts, and had a backup at the ready while the forge was hot. The next pour, I used a funnel made from metallic duct tape instead of the pouring basin. The website calls it a kush cup. This time it was successful. I really enjoyed this type of casting in place of greensand. I have no idea how successful it would have been attempting to pull a wooden pattern with cores in this scale.
sprued and dipped.jpg
successful.jpg

The casting ended up shorter than I planned lengthwise, but was able to make it work. Look at the front edge. It machined up nicely, and was able to open the ports using a burr bit and drills. It was cast solid.
machined.jpg
 

raveney

Well-Known Member
Joined
Mar 16, 2018
Messages
47
Reaction score
77
Location
Central Florida, USA
Some lessons learned in this post;

The next parts made are valve covers, water pump, thermostat housing, fuel delivery. I didn't capture a lot of machining setups during this part of the build.
I used a 12 Volt power supply and vinegar/salt water to Nickle plate some small parts during this time. Later on I plated the headers previously shown.

Had a mishap while plunge cutting the cavities in one valve cover. The part was inverted in the vise, and the end mill grabbed and pulled the part up resulting in a unintended see through/cutaway engine feature. I think a piece of paper between the part and jaw would have prevented this.

I also learned that when the small sacrificial piece of Nickle starts to get smaller, do not use any wire between the alligator clip and the material to suspend it deeper in the solute. The wire will become the cathode or anode. So I now realize that one can copper plate and stainless plate using this mistake.

One more silly thing that I did. On the linkage connecting the carburetors I used a 0.094 small bit of scrap drill rod as a shaft. I also used this part to hold the bell-crank levers while I soldered them. Later in the project, I wanted to cross drill these and pin onto the shaft. Guess what happens when you attempt to drill through 0-1 steel after it has been heated and cooled? Yep, It's rock hard and small bits will dull rather quickly and shatter.
 

Attachments

  • electro plating setup.jpg
    electro plating setup.jpg
    2 MB · Views: 0
  • linkage.jpg
    linkage.jpg
    6.1 MB · Views: 0
  • valve covers.jpg
    valve covers.jpg
    7.8 MB · Views: 0
  • velocity stacks.jpg
    velocity stacks.jpg
    1.6 MB · Views: 0
Top