Model Engine Maker

Engines => Your Own Design => Topic started by: Longboy on September 01, 2017, 06:25:59 PM

Title: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 01, 2017, 06:25:59 PM: "PREMIERING SOON" :atcomputer:

(http://i.imgur.com/CVYl3br.gif) (http://imgur.com/CVYl3br)
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: b.lindsey on September 01, 2017, 06:46:19 PM: I am sure it will be a good project Longboy. Don't happen to have a better picture of it do you. Hard to tell much from that one. :???:

Bill
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 01, 2017, 07:10:15 PM: Of course I do Bill.....but I want to open up a new posting with a teaser photo of my latest! ;D
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: crueby on September 01, 2017, 07:51:58 PM: Quote from: Longboy on September 01, 2017, 07:10:15 PM
Of course I do Bill.....but I want to open up a new posting with a teaser photo of my latest! ;D

As long as we don't have to sit through the infomercial!!! :lolb:
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 01, 2017, 09:12:03 PM: :thinking:.....I don't think anyone ever got more gray hairs during my presentations. ;)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Intro.
Post by: Longboy on September 02, 2017, 05:56:57 PM: Twin cylinders, four cylinders....gotta be something in between. Coming back again from their forgettable intro in the automotive world in the 80-90's is the 3 cylinder engine. From Ford Fiesta and Mini Cooper as the latest offerings to Yamaha's biggest seller in large motorcycles, 3 cylinders are making headway in efficient, high output applications in small cars cutting the cost of driving. In the case of the BRATZ engine, it's a look back at historical means of power by 3 cyl. engines found in industrial and agricultural usage. After the single cylinder and excluding aviation radials, it is uncommon to find odd number cyl. engines being modeled.....let me show you my version! :D

(http://i.imgur.com/uOA9t4F.jpg) (https://imgur.com/uOA9t4F)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Crankshaft.
Post by: Longboy on September 03, 2017, 07:21:07 PM: BRATZ is the same design with some valvetrain changes as the BEST FRIEND engine. The crank is a heavier unit using .250in. throw pins in each pair of 1.75 in. dia. crank webs @ .50 in. height.

(http://i.imgur.com/07sBZ34.jpg) (https://imgur.com/07sBZ34)

4 main bearings. Center brass and end Oilite bushings. Aluminum Parksy design cradle in black satin. Unit weighs just under 4 lbs.

(http://i.imgur.com/ZEAg2C5.jpg) (https://imgur.com/ZEAg2C5)

(http://i.imgur.com/mC3hcHR.jpg) (https://imgur.com/mC3hcHR)

10-32 set screws with blue Loctite hold the throw pins, upsized from #8's for a better grip in build progress.
Title: Re: Longboy's "BRATZ" Model Gas Engine. Block.
Post by: Longboy on September 04, 2017, 10:42:35 PM: A 6 in. long block receives some 1.125 in. bore DOM liners at a 2 in. bore spacing.

(http://i.imgur.com/II9QYPa.jpg) (https://imgur.com/II9QYPa)

The block is relieved for the cam drive sprocket and the block hugger camshaft along its length to clear the lobes.

(http://i.imgur.com/PAXTC1r.jpg) (https://imgur.com/PAXTC1r)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Valvetrain.
Post by: Longboy on September 05, 2017, 11:57:56 PM: This is the lifter bar. Exhaust valves only. Brass guides are set screwed in. Bar screwed above camshaft into block.

(http://i.imgur.com/aDX4Faz.jpg) (https://imgur.com/aDX4Faz)

The lifters themselves are rivets found in the fastener bins over at ACE Hardware so I don't even bother making my own. The mushroom will be turned down to a smaller diameter to clear cam lobe set screws. A flat is milled on the mushroom dome to ride the cam lobe and the stem is drilled down into to take a piano wire push rod.

(http://i.imgur.com/1KcXU7m.jpg) (https://imgur.com/1KcXU7m)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Valvetrain.
Post by: Longboy on September 06, 2017, 09:30:48 PM: A 3/16 in. shaft with cam lobes of 3/8 in. CR. The drive is by MXL sprockets. Brass bearing on shaft end and a roller bearing in sprocket guard.

(http://i.imgur.com/TBncEm2.jpg) (https://imgur.com/TBncEm2)

(Thats a funny looking brass lobe on there Longboy! :thinking:) ..... :D I'll get to that next post.

(http://i.imgur.com/wIW2PlR.jpg) (https://imgur.com/wIW2PlR)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Electrics.
Post by: Longboy on September 07, 2017, 10:29:01 PM: A distributor at a right angle to camshaft is a change up from previous engines. Compact and close to block, its distributor cap is a 3/4 in. internal dia. PVC end cap.....

(http://i.imgur.com/7wZjxUt.jpg) (https://imgur.com/7wZjxUt)

......while the rotor is Delrin, a #4-40 SS screw over a brass tab passes the coil voltage on to the spark plug leads.

(http://i.imgur.com/8s37T8p.jpg) (https://imgur.com/8s37T8p)
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 08, 2017, 08:57:00 PM: The camshaft and lifter bar mounted to block.

(http://i.imgur.com/aE4Jw7z.jpg) (https://imgur.com/aE4Jw7z)

Distributor just clears the lifter bar. :ThumbsUp: Radiator fins relieved for the lifter guides.

(http://i.imgur.com/sM3gFtt.jpg) (https://imgur.com/sM3gFtt)

The bevel gears are 24T at .5 modulus. Just the right scale! Knurled screws retain the distributor cap.

(http://i.imgur.com/2yGb2Lg.jpg) (https://imgur.com/2yGb2Lg)
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: simplyloco on September 08, 2017, 09:13:54 PM: I'm really looking forward to seeing this thing running!
John
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 11, 2017, 02:36:59 AM: An intake valve block and manifold.

(http://i.imgur.com/sTlRHtj.jpg) (https://imgur.com/sTlRHtj)

Delrin manifold has Traxxas carb on a pipe fitting angled out just enough for carb body to clear.

(http://i.imgur.com/5h5onTE.jpg) (https://imgur.com/5h5onTE)

An O-ring around the valve guide makes the seal between the two pieces.

(http://i.imgur.com/nGY6DR2.jpg) (https://imgur.com/nGY6DR2)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Cylinder head.
Post by: Longboy on September 13, 2017, 06:22:26 AM: The head fining a tedious operation. By pattern to get around various holes and execution time. Eighteen rows @ two or three passes to get the depth. With shallow combustion chamber and a one inch height aluminum stock, the brass valve guides are near flush with the top of head.

(http://i.imgur.com/FSJ8uw4.jpg) (https://imgur.com/FSJ8uw4)

On the exhaust side, a pair of ports are symmetrical for #2 & #3. but #1 had different ideas and went in another direction.....the black sheep of conformity. :Lol:

(http://i.imgur.com/bvkySPc.jpg) (https://imgur.com/bvkySPc)

Plenty of room in this chamber with a 1.125 bore. 10mm threads for CM-6 spark plugs and single ex. valve. The relief milled into the spark plug thread is for the intake port as the ports were above depth of combustion chamber. Tiered circles around chamber would be inner for cylinder liner seat and the outer tapered for the O-ring seal.

(http://i.imgur.com/996PmkE.jpg) (https://imgur.com/996PmkE)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Rod/ Piston.
Post by: Longboy on September 14, 2017, 01:05:56 AM: The piston and rod assembly lightened on the con rod, they weigh 1.34 oz. Roller bearings in small end, no bearing inserts in big end.

(http://i.imgur.com/HMYkJ0K.jpg) (https://imgur.com/HMYkJ0K)

The O rings on the pistons are Metric riding on an inch sized bore. Close but slightly smaller outside diameter....I hope they don't give me grief losing compression in running. :facepalm:

(http://i.imgur.com/IfvF3nt.jpg) (https://imgur.com/IfvF3nt)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Valvetrain.
Post by: Longboy on September 14, 2017, 09:17:56 PM: The rocker arms and their pedestals are all brass with SS hardware. Easier to cut and shape than steel arms in this scale.

(http://i.imgur.com/2Fvizlz.jpg) (https://imgur.com/2Fvizlz)

With half of the valve spring below the head surface the rocker assembles show a low profile compact fit as do the spark plugs to the cylinder head. There are no lock nuts for the push rods. :o Drilled for a 6-32 threaded hole, the 3/32 in. dia. piano wire push rods slip up in the arms and a set screw within then maintains the valve clearance. Some blue Loctite on set screw holds its position.

(http://i.imgur.com/i5Z8EBO.jpg) (https://imgur.com/i5Z8EBO)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Cooling.
Post by: Longboy on September 15, 2017, 10:51:51 PM: Using heat sink material on the BEST FRIEND engine worked so well I bought some more with greater fining area and bolted to the perimeter of the cyl head.

(http://i.imgur.com/s4zF3eG.jpg) (https://imgur.com/s4zF3eG)

Also a couple bars on the upper engine block, BRATZ has little chance of becoming a hot head in the Arizona summer. :ThumbsUp:

(http://i.imgur.com/8jM6JBb.jpg) (https://imgur.com/8jM6JBb)
Title: Re: Longboy's "BRATZ" Model Gas Engine. Assembly.
Post by: Longboy on September 17, 2017, 06:34:51 PM: Almost finished here, the top side of engine.

(http://i.imgur.com/masN1Cr.jpg) (https://imgur.com/masN1Cr)

Block and head with all external components except wiring. Tecumseh points supply the coil spark.

(http://i.imgur.com/MDsJ6TX.jpg) (https://imgur.com/MDsJ6TX)

The legs on the crank cradle. The three slots allow pass through of rod caps to separate rods from crank shaft while in the cradle.

(http://i.imgur.com/Mi5jxP8.jpg) (https://imgur.com/Mi5jxP8)

Loading of the bores joining crank to block.

(http://i.imgur.com/zLgmPJN.jpg) (https://imgur.com/zLgmPJN)
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 18, 2017, 06:17:01 PM: The "BRATZ" engine is now completed! :whoohoo:

(http://i.imgur.com/ZfscH9S.jpg) (https://imgur.com/ZfscH9S)

Work was started first week of April.

(http://i.imgur.com/ECHRqYL.jpg) (https://imgur.com/ECHRqYL)

Finished early July and up and running well about 10 days later.

(http://i.imgur.com/tSCZ586.jpg) (https://imgur.com/tSCZ586)

The largest flywheel I have used, spacers under the feet were added later to clear my hand for hand starting.

(http://i.imgur.com/fCIoNXj.jpg) (https://imgur.com/fCIoNXj)

Troubleshooting the fuel and timing to get the right sound, more displacement and same size exhaust porting as the BEST FRIEND engine gives a sharp Ba-Brat cadence to the exhaust pipes, hense its namesake.

(http://i.imgur.com/QTCV4LD.jpg) (https://imgur.com/QTCV4LD)

My first summer build of an engine. :o I suffered greatly :ROFL: .....in the 90deg garage :LittleDevil:.....I just couldn't help myself! :shrug:

(http://i.imgur.com/ukV87po.jpg) (https://imgur.com/ukV87po)

But the job gets done! :ThumbsUp:

Come back now for the video and more photos! :popcorn:
Title: Re: Longboy's "BRATZ" Model Gas Engine. Proof of Life.
Post by: Longboy on September 19, 2017, 10:14:29 PM: Welcome to the "proof of life" video of the BRATZ engine. Enjoy! :cheers:

(http://i.imgur.com/rTFDTXd.jpg) (https://imgur.com/rTFDTXd)

(http://i.imgur.com/Jjh7oI4.jpg) (https://imgur.com/Jjh7oI4)

(http://i.imgur.com/KOxvhgJ.jpg) (https://imgur.com/KOxvhgJ)

(http://i.imgur.com/ro1tkV4.jpg) (https://imgur.com/ro1tkV4)

(http://i.imgur.com/Hz3eaC4.jpg) (https://imgur.com/Hz3eaC4)

(http://i.imgur.com/y3OclzN.jpg) (https://imgur.com/y3OclzN)

(http://i.imgur.com/uiuanU9.jpg) (https://imgur.com/uiuanU9)

(http://i.imgur.com/ZnEI4tE.jpg) (https://imgur.com/ZnEI4tE)

:popcorn:
https://www.youtube.com/watch?v=vs7Yh_FAWi8

Thanks for following along on this presentation! Dave.
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: yogi on September 19, 2017, 11:15:48 PM: Well done Dave!!! :ThumbsUp: :ThumbsUp: :ThumbsUp:
Runs fantastic.
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Gas_mantle on September 19, 2017, 11:33:34 PM: Great engine Dave, one to be proud of :)
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Nick_G on September 19, 2017, 11:38:09 PM: .
That is totally ace. :)

Nick
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: b.lindsey on September 20, 2017, 12:39:42 AM: Very nice runner Dave. The slow speed is fantastic to listen to as well !!

Bill
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Dave Otto on September 20, 2017, 01:18:30 AM: Nice work Dave!
She runs real nice!

Dave
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: ShopShoe on September 20, 2017, 01:26:05 PM: Nice Work and a good runner.

I enjoyed your posts, too.

--ShopShoe
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 20, 2017, 08:59:46 PM: Thanks fellow modelers! :Love: Dave.
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Brian Rupnow on September 20, 2017, 11:47:01 PM: Very nice build. It looks good and runs good.---Brian
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Plani on September 21, 2017, 07:49:01 AM: Congratulations to this really nice running engine! :ThumbsUp: :ThumbsUp: :ThumbsUp:
And the O rings on the pistons seem to work well too. Did you check them yet?

Plani
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: cfellows on September 21, 2017, 05:03:32 PM: Very nice engine. Lots of innovation, very well done!

Chuck
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 22, 2017, 05:00:10 AM: Quote from: Plani on September 21, 2017, 07:49:01 AM
Congratulations to this really nice running engine! :ThumbsUp: :ThumbsUp: :ThumbsUp:
And the O rings on the pistons seem to work well too. Did you check them yet?

Plani
Engine runs well so they are holding compression. 5% WD40 mix with fuel. Dave.
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: rudydubya on September 22, 2017, 07:09:52 AM: Well done, Dave. Beautifully crafted. I like its slow idle.

Regards,
Rudy
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on September 22, 2017, 05:50:33 PM: The heavy brass flywheel and its 3 1/2 in. diameter give BRATZ that low rev industrial idle. For a hand start, it is about the max diameter I can get a flip grip upon. I believe a 3 in. dia. flywheel to be more ideal in this scale for similar RPM idle speeds plus keep a low crankshaft center of gravity profile. A 3 1/2 dia is used on my FOREMAN 4 cyl , made the same speed reduction. I'm sure the extra cylinder contributed to the smoothness too. Thanks to a senior modeler who brought up the benefits of large dia flywheels and idle quality during FOREMAN's build. :D Dave.
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Roger B on September 22, 2017, 06:15:32 PM: Excellent :praise2: :praise2: I've only just caught up on this thread. I have always liked the sound of a three cylinder engine :ThumbsUp: :wine1:
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on November 21, 2017, 06:33:40 AM: Does sound unique to me.
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: ThomasM on November 22, 2017, 08:16:51 AM: Hello Dave,

Your design is perfect for relaxing while just watching and listening to the engine.
Everything is visible and the low idle is perfect.
Maybe with a larger flywheel and smaller carb it would be possible to idle it even slower.
The o-rings in the cylinders should provide enough compression at even lower rpm.

This or something similar has just became part of my to do list.

Best regards,
Thomas
Title: Re: Longboy's "BRATZ" Model Gas Engine.
Post by: Longboy on December 19, 2017, 04:54:16 AM: You are welcome Thomas. Inspiration from model engine videos activates the soul of desire! Good luck in your designs. :ThumbsUp: