Author Topic: Triumph 650 Twin Engine  (Read 28595 times)

Offline JR72

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Re: Triumph 650 Twin Engine
« Reply #15 on: March 23, 2017, 07:36:14 AM »
Hi Mike
I was alerted to your thread by my friend Chipswitheverything who is a brilliant model engineer and a master at woodwork. (don`t you just hate these people) he knows I have a love of British motorcycles so I will be watching your project very closely and looking forward to your first photos.

It`s going to be some project so the very best of luck.

John

Offline mikemill

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Re: Triumph 650 Twin Engine
« Reply #16 on: March 24, 2017, 06:05:37 PM »
I decided to make the con rods first as they are relatively simple items. Working with CNC requires a different approach to optimize the capabilities of the process. The various steps described from the top down.
1)   Cutting the basic shapes from 1/2 in ali
2)   Centre drilling holes
3)   Cutting the rebate with a ball cutter
4)   Facing the front
5)   Cutting radius on sides
6)   Boring the shims
7)   The finished items

Mike

Offline Vixen

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Re: Triumph 650 Twin Engine
« Reply #17 on: March 24, 2017, 07:07:08 PM »
Nice work there Mike.
Good luck with the rest of the engine

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Flyboy Jim

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Re: Triumph 650 Twin Engine
« Reply #18 on: March 25, 2017, 02:18:30 AM »
Nice parts and good documentation Mike! Well done.

Jim
Sherline 4400 Lathe
Sherline 5400 Mill
"You can do small things on big machines, but you can do small things on small machines".

Offline mikemill

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Re: Triumph 650 Twin Engine
« Reply #19 on: March 30, 2017, 06:06:33 PM »
The next item to tackle is the crank which has a central flywheel, carved out of a 1in thick 4in dia lump of cast iron. The webs where milled out of 1/2in mild steel, and the pins and central shaft are precision ground mild steel (PGMS).
The components are temporally assembled the make adjustments to balance the flywheel, I could have left a bit more meat on the counter weight of the flywheel as I had to drill some holes in the opposite of the rim to get the balance right, you live and learn!!
1)   The finished flywheel
2)   Cutting out the webs
3)   Facing and reaming the webs
4)   Balancing the flywheel

Mike



Offline 90LX_Notch

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Re: Triumph 650 Twin Engine
« Reply #20 on: March 30, 2017, 06:50:44 PM »
Very nice work Mike.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Admiral_dk

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Re: Triumph 650 Twin Engine
« Reply #21 on: March 30, 2017, 09:37:38 PM »
I really like the look of your crank  :praise2:

... but I can't help thinking that you need some of the weight of the conrods put on to balance it correctly ....  :noidea:

Best wishes

Per

Offline gbritnell

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Re: Triumph 650 Twin Engine
« Reply #22 on: March 30, 2017, 09:52:14 PM »
I agree with Per. You need to take into account some of the weight of the rods to be more accurate.
gbritnell
Talent unshared is talent wasted.

Offline Art K

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Re: Triumph 650 Twin Engine
« Reply #23 on: March 31, 2017, 12:40:01 AM »
Mike,
I've been following along and agree with Per & George. You need to account for the weight of the piston and rod assembly on the crank throw. Otherwise the crank will be balanced to itself and then you add them & its out of balance again. Great work, I love old motorcycles.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline mikemill

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Re: Triumph 650 Twin Engine
« Reply #24 on: March 31, 2017, 09:01:54 AM »
Thanks for your encouraging remarks, I am no expert on engine balancing but taking my que from the Triumph manual which shows an illustration of a crank being balanced without rods, also racing engine cranks are balanced at high revs on a lathe without rods.
My understanding is to balance the rotating mass rather than the reciprocal components? But willing to take advice from those with more experience.

Mike

Offline Bluechip

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Re: Triumph 650 Twin Engine
« Reply #25 on: March 31, 2017, 09:18:23 AM »
Mike,

Download this :

http://tuningforspeed.com/files/Tuning_for_Speed.pdf

Page 107-ish. There are 2 pages per screen so the pagination on the l/h side is awry ...  :headscratch:

It's P59 on the l/h side ..



 May help  :ThumbsUp:

Dave
« Last Edit: March 31, 2017, 09:22:47 AM by Bluechip »

Offline mikemill

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Re: Triumph 650 Twin Engine
« Reply #26 on: March 31, 2017, 11:32:35 AM »
Thanks Dave good info, checking the Triumph manual I did not notice two weights on the pins to represent part of the weight of the rods, so back to the drawing board!!!
It’s all part of the fun.

Mike

Offline billmac

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Re: Triumph 650 Twin Engine
« Reply #27 on: March 31, 2017, 12:23:24 PM »
You cannot fully balance a parallel twin or a single; the best you can do is a compromise. Unfortunately the compromise that will give the smoothest running depends strongly on how the engine is supported. If you change the balance factor, you will change the direction in which the greatest out of balance forces will appear. Typically the balance factor is set so that those forces are aligned with the stiffest direction of the supporting frame. I guess you haven't finalised the design of the engine plates that you will hold the engine in, so you may want to wait until you can run the engine and then experiment with balance factor.

The weight you need to represent the con rods is not the entire conrod weight. The bottom end of the rod shares most of the motion of the flywheel; the top end is mostly travelling in a straight line, so you need a compromise here as well.

Parallel twin engines are full of compromises. If you choose well, you get a good engine. If you try to extract too much power, you get a buzzy vibrating engine with a tendency to grenade. This is probably not an issue with your model of course.

This is a great project - keep up the postings.

Offline MJM460

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Re: Triumph 650 Twin Engine
« Reply #28 on: March 31, 2017, 12:47:36 PM »
Hi Mike,

Bill Mac beat me to it with his really excellent and practical reply, so I hope my contribution can still add something.  My work on reciprocating compressors required me to have some basic understanding of how they are balanced and what forces have to be considered in foundation design.  There are many factors that also apply to your engine.  Here they are as I understand it, (with attendant risk of very heavy theory).

First you cannot include the con rods on the balance machine because the little end flying around would make the result invalid apart from requiring a lot of room under the safety guards.  So the crankshaft is balanced with an equivalent mass attached to the crankpin to represent the con rod effect.

Second, you cannot balance a reciprocating mass with a rotating one, though you can do it with two masses rotating in opposite directions, not a useful solution in your case.

The big end rotates with the crank pin and can be well represented by attaching the appropriate mass at the crank pin.  Obvious when you think about it.  In practice a slightly larger mass is included to allow for part of the conrod that has significant rotating component to its motion.  Experts can calculate the allowance but I did not get too close to this aspect after the relevant lecture over 50 years ago.

For a multi cylinder engine, in addition to the reciprocating forces introduces out of balance couples as the forces are not in line. The different crank positions can be set out to balance each other.  Horizontally opposed (think BMW) is easiest, but still leaves an oscillating couple about a vertical axis.  I think your twin is vertical in line, if the cranks are at 180 deg, the vertical reciprocating forces balance each other but leave an oscillating couple about a horizontal axis perpendicular to the crank shaft.  Four cylinder in line or opposed and six cylinder engines can be arranged to reach nearly perfect balance of forces and couples.  However this still does not allow for the uneven forces due to compression and power strokes which on some configurations conflict with requirements due to the moving masses so some adjustments/compromises have to be made as bill Mac has explained.

I hope there are some still reading and that this helps in some small way.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Mosey

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Re: Triumph 650 Twin Engine
« Reply #29 on: March 31, 2017, 02:02:35 PM »
Thin, stainless Safety wire through a hole drilled in the nut retaining engine bolts is common practice on piston aircraft, racing automobile, and racing motorcycle engines to keep things from vibrating off. The wires are threaded through the nut and then twisted with a special plier-like spin tool and tied off to an nearby spot. All the wires are a pain for the guy who has to service the motor but good insurance against scattering engine parts. I did once hear the rings disintegrate and rattle through the exhaust canister due to a slight leanness of carburation. Drilling all those tiny nuts is good training for small hole drilling but consumes lots of manganese drill bits even with a drill jig.   :stir:
Mosey
« Last Edit: March 31, 2017, 02:06:42 PM by Mosey »

 

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