View Full Version : V-twin (my own design)

03-17-2010, 03:09 PM

This past August I started designing a small v-twin engine. I wanted something different so the reason for my own design. All the parts were made from solid, no castings. It has a 1.00 bore and an 1.25 stroke. It's a 90 degree configuration. The main parts are 6061 aluminum with a steel crank and steel forked rods. The crank rides on sealed ball bearings but there is an oil pump to feed the rods, gears and cams. The heads are 7075 aluminum with bronze guides and steel seats. The valves are stainless steel. The ignition is electronic fired by a Hall trigger with a timing disc. It is a dual fire system with a waste spark on both cylinders.

Here's a link to Youtube of it running for the first time. It needs a little carb work but other than that it's just about complete.

Doc Nickel
03-17-2010, 03:16 PM
Very nicely done! I love it.

Got any in-progress build pics, or shots of tricky fixturing? :D


Al Messer
03-17-2010, 03:20 PM
Good looking job!! Congratulations!

03-17-2010, 03:23 PM
Hi Doc,
There's the complete build with pictures, from the first block of aluminum up to making the exhaust pipes on HMEM.

Bill in Ky
03-17-2010, 03:24 PM
You did a great job on that engine!!

03-17-2010, 03:24 PM
Wow, incredible craftsmanship and design!

03-17-2010, 07:00 PM
Beautiful job as usual George. Can we look forward to seeing it and you at NAMES this year?

03-17-2010, 07:03 PM
Wow! That is really fantastic craftsmanship!


03-17-2010, 07:03 PM
I'll be there Jim. Only death and taxes would keep me from going. It's one of the few places to socialize with all the modeling types.

03-17-2010, 07:41 PM
Beautiful creative workmanship!!

gary hart
03-17-2010, 07:43 PM
George, WOW, awesome. Mighty nice and great inspiration. Thanks for sharing.

03-17-2010, 07:50 PM
that is really cool great job man

03-17-2010, 08:58 PM
I like that - any plans available?


03-17-2010, 09:15 PM
Looks great. I look forward to seeing it at the NAMES show.

03-17-2010, 09:27 PM
I'm in awe! That is really amazing. I like your starter setup. You do realise that you can't do good work on a round column mill thought don't you?

03-17-2010, 09:42 PM
Nice work........has the real rumble and shake........can't let go of the fuel can for long...........LOL

03-17-2010, 10:01 PM
Thanks everyone. Chris, they keep telling me that but I don't know what they mean. lol. Pete, I have a complete set of plans, 15 sheets. When I get the carb fine tuned I'll change the last sheet and then I'll have them available.

Tony Ennis
03-17-2010, 10:03 PM
It's gorgeous!

03-17-2010, 10:08 PM
I'm in awe! That is really amazing. I like your starter setup. You do realise that you can't do good work on a round column mill thought don't you?

Yeah, don't show the guys on the Practical Machinist site. They won't believe you could have built that on those machines.

A good friend of mine has one of the nicest model engine collections I have seen and his shop has a round column mill and an older Atlas lathe and a 9x20import lathe. It's unbelievable what pure determination and a skilled hand can turn out with these lowly machines.

Seriously Gbritnell, that is some nice looking work and I appreciate you sharing it with us. It was neat seeing the progression of the engine on the model site.

03-17-2010, 10:10 PM
Very nice. Something that few can do.

03-17-2010, 10:14 PM
Excellent as always!

Don Young
03-17-2010, 10:14 PM
I am really impressed with the design, the workmanship, and how well it ran in the video. Good job!

03-17-2010, 10:53 PM


03-18-2010, 11:05 PM
That was an absolutely fabulous thread (to heap superlative upon superlative). I had the advantage of seeing it full bloom but it must have been a treat for those who saw it to watch it grow. Great photography and descriptions. Almost felt at times like I was looking over your shoulder as you whittled away with the files.

Before I'd read a word the question crossed my mind: "how did he do those nice castings?"! Surprise surprise!

That gem should draw a pretty good crown ^H^H^H^H^H^ crowd at NAMES :D

As a Harley owner, I am partial to V-twin pushrod engines - especially when you can see all the parts. The pickle fork rod set was excellent! Thought I was watching the assembly of a Harley shovel head.

03-18-2010, 11:19 PM
way to go George, another beauty!

03-19-2010, 12:43 AM
gbritnell I'm awe struck... I had to read the complete thread last night. And when I saw that you used a mill drill to do this I was further impressed if that was possible. To see this emerge from blocks of aluminum and chucks of steel. I would love to attempt this build when plans are made available. A true artisan be it crank or pencil that's what you are.... I tip my hat.

03-19-2010, 01:20 AM
Very awsome show of skill and planing!
Iv wanted to make a motor but allways too.. lazy.
Any pics of the inside of the carb?
Seems that website url is down...

03-19-2010, 01:21 AM
That's wonderful! Not to mention outstanding. Or better than that.

As far as the stalling, a certain Electronics Engineer I once knew used to say,
"It worked Once! It's a 'Maintenance' problem!"

Nice work. The mind boggles!


03-19-2010, 02:06 AM
Wow, just wow...!

03-19-2010, 02:27 AM
Hi Doc,
There's the complete build with pictures, from the first block of aluminum up to making the exhaust pipes on HMEM.

Nice engine! The link says "forbidden" however.

03-19-2010, 02:44 AM
They have throttled bandwidth so those warnings come and go. Keep trying as it is well worth the visit. That needs a better home.

03-19-2010, 08:15 AM
Oh WOW, finaly got to see the step by step, AMAZING.
http://img.photobucket.com/albums/v43/gbritnell/V%20TWIN/GA.jpg Love the scale and attention to detail of parts not normaly seen. even your crank rods look like peices of art.

http://img.photobucket.com/albums/v43/gbritnell/HJ.jpg wow, one of the best engine interiour shots I have ever seen, I LOVE the gearing!

03-19-2010, 08:51 AM
That is a very nice engine.
My personal thoughts are that all these model things are too small to be of any use. Now, if that engine was of the scale that you could use it on a mini-bike or a go-cart, then that would be serious fun! Think like the live steam guys with the trains you can actually ride on. That beats the hell out of the HO trains running around the Christmas tree, right??


Deja Vu
03-19-2010, 09:24 AM
Beautiful creative workmanship!!

Ditto!.... as well for all your other creations.

03-19-2010, 09:46 AM
Nah that would be an awsome motor for a skateboard or a little kits scooter, Or a RC car/motorbike, Even a small robot connected to an alternator for powering it.

03-19-2010, 12:00 PM
Beautiful machine! Sehr gut! ;)

Somehow reminds me of the Hogglet (from MEB), but much more refined.


03-19-2010, 12:38 PM
Are the pipes (exhaust/intake) welded, brazed or ??

03-19-2010, 06:37 PM
WOW!!! That thing is ridiculous...need to put that on my "to do" list.

oil mac
03-20-2010, 04:00 PM
Absolutely superb craftsmanship

Alistair Hosie
03-20-2010, 06:04 PM
Well done george .A great piece of fine engineering your the man as they say. I wouldn't even know how to buy one ready made:D Alistair

03-23-2010, 07:52 PM
Thank you one and all for the gracious comments.
To answer some of the questions that were posed, yes there are drawings available for it. I just finished the last sheet the other day. The pipes were formed out of .375 thinwall stainless tubing (304). I made a bender and filled the pipes with Cerro alloy to prevent them from collapsing. The two sections have an overlapping collar that is silver brazed. Because the pipes have compound bends and have to fit through the base I thought this would be the most expeditious way of making them.
I have since made a few changes to the engine and base. Running it has brought out some needed modifications. The intake manifold got too hot and was percolating the gas back into the fuel line so I took the manifold off and machined .04 from the flanges. I then made some insulator blocks and that cured the problem. The next issue was the engine to base mounting screw. They started out as 3-48's but kept coming loose so they are now 5-40's. Likewise with the upright supports to the runners. I added another screw at each corner and increased the sizes.
I guessed at the timing when I first started it (15 degrees). With it shaking somewhat I kicked it back to about 56 degrees. It still runs well but has tamed it down a little.
The last adjustment was just playing with the carb. I have it now where it will idle at a steady 900 rpm and rev up to about 4500 rpm. It will rev higher than that with a little carb tweaking but Lord does it shake.
All in all I'm thoroughly happy that the finished engine proved out the design. I did go back and add a little stock to the heads and take a little from the pistons to reduce the compression ratio somewhat. It has so much compression now that it's all you can do to turn it past TDC by hand.