Author Topic: Big stroke 55 cc one cylinder ICE  (Read 20216 times)

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #90 on: September 25, 2022, 08:04:59 PM »
First order balance shafts

So time to calculate and design first order balance shafts.

Let's say we add 100% of oscillating mass to crank counter weights.

m rot = 0,209 kg ; m osc = 0,081 kg ; %m rot = 1 ; %m osc = 1

Mass counter weights crank = m normal balance = 1/2 * ((%m rot) *m rot + (%m osc) * m osc) * radius crank / r balance = 1/2 * (1*0,209+1*0,081)*(0,023/0,01596) = 209,4 gram

r balance changed now because we added weight to the crank, but not even and that changed or r balance distance.

Picture 1 shows designed counter weights to almost the calculated weight and r balance (y value 3D CAD). 208,2 gram.


Spinning this crank create a force horizontal of this engine view.

To design the first order mass of each balance shaft we have to calculate the counter weight of 1st order. It is like the same calculation of the crankweb but only there we to deal with only oscillating mass! And r balance (y value 3D CAD) have to come from CAD to put in the calculation.

mass 1st order counterweight = m 1st = 1/2 * m osc * (radius crank/r balance 1st) = 1/2 * 0,081 * (0,023/0,00983) = 0,0953 kg = 95,3 gram

To check this we calculate 1st order force and than the needed mass. for example n= 3000 rpm = w 314,2

First order force = F1 = m osc * r crank * w^2 = 0,081 * 0,023 * 314,2^2 = 185 N

Calculating the needed mass

F=m*a = m*r*w^2     =>   m=F/(r balance 1st*w^2)

Mass 1/2 for two shafts = 1/2* 185/(0,00983*314,2^2) = 0,0953 kg = 95,3 g



Picture 2 shows the designed 1st order counter weight that should be welded to a 10mm shaft.

Picture 3,4,5 display the designed balance shafts in the current crankcase.

The original back plate of the crankcase need to boring two 46mm holes. Using a boring bar it is for me difficult to turn this to a good tight dimension for a bearing.
So idea to turn bearing housings on tolerances. Add a o-ring to seal it. Shim the counterweight shafts and then lock it with a locking assembly.
It would be great if there are large OD shims available to also lock up the bearing axial. Or other I could use a tight fit or loctite on the bearing-housing.

The first order balance shaft should turn above current oil level. And have some clearance with the crankcase profiles.

Using 3x Black POM spur gears. d=54mm z=36 module 1.5. The width is 10mm but can be turned to thinner or thicker dimension because they came as 15mm thick. POM has a max surface pressure of 22 N/mm2. With 10mm width of gears you have a max teeth force of around 330 N -> 9 Nm of torque.
First I was thinking of using one brass and tow C45 gears. But POM is strong enough, less sound, I think no need of lubrication and lightweight.



In the crankcase there is room to fit a second order balance shaft. Weight of the counterweight is around 45 grams with a radius of 15 mm. Maybe one shaft (the one that have to turn same direction as crank) can be powered by the T5-10 valve timing belt. Need to designed.

For now. Only 2x 1st order shafts take 76,5% of total unbalance forces. And with one 2nd order shaft 88,3 %
« Last Edit: September 25, 2022, 08:12:32 PM by AlexS »

Offline Admiral_dk

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Re: Big stroke 55 cc one cylinder ICE
« Reply #91 on: September 25, 2022, 10:20:00 PM »
I might be a bit Thick here .... but why are you using two Balance-Shafts running the same speed as the Crank ...???....  I have never heard of any benefits from that approach ....  :noidea:

OK - just before pressing Post - I realized that the Crank + Balancer + Piston -> will result in a 'Rocking-Couple' and that can be elliminated with two Balancers ...!... but I have yet to see a production Engine with two running same speed  :thinking:


I forgot to respond to your RD250. I never saw one off these here in DK - but I had the 'Pre-Curser' to the RD350, as my first registrated MC was a R5-F from 1971.
Double Leading Drum-Brakes .... Freshly cleaned and one finger was enough to lock the Front + a week later you could pull the Leaver all the way into the handlebar and still pray for more braking power ...  :o
Clean & Repeat   :Doh:
It was also the last model with Piston-Controlled Induction ....  :(
I had some good times on that bike - but I sold it after eight months .... and even though I was a Die-Hard two-stroke fan until that bike - Way too Many problems => I have only own Four-Strokes since ....

For those that ride more sensible than I did - not neccesarily a problem .... and I hope that your RD serves you well  :LittleAngel:    :cheers:

Per

Offline ShopShoe

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Re: Big stroke 55 cc one cylinder ICE
« Reply #92 on: September 26, 2022, 01:14:50 PM »

"... but I have yet to see a production Engine with two running same speed."


Saab used two balance shafts for awhile in a 4-cylinder engine, an interesting concept:

http://www.saabwiki.info/index.php?title=NG_900/9-3_Balance_Shafts

--

--ShopShoe


Offline Roger B

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Re: Big stroke 55 cc one cylinder ICE
« Reply #93 on: September 26, 2022, 02:30:53 PM »
Older Saabs also used the Ford V4 as mentioned in the book extracts which had a single balance shaft.

As I understand the  twin shafts have to rotate in opposite directions so that the horizontal forces cancel out and the vertical forces balance the reciprocating piston.
Best regards

Roger

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #94 on: September 26, 2022, 06:20:24 PM »
Good question.

Yes I think that Roger is right.

I think it is possible to use one primary balance shaft to counter the oscillating mass (piston ass. + half part is of connecting rod). I saw that on a 250cc motocross engine. I quest two shafts is more complex, space and costs. They may balance a % of oscillating mass and balance this also in % so there is still both vertical as horizontal 1st order forces. These forces result in a total lower forces that are less observable. I have read that vertically a engine and frame lever the forces better. And have taken the rocking movement for granted.



Years ago for a school project combined with a tractor pulling team / engine workshop we try to design a single cylinder test engine of one of them 8.8L big block chevy's. A challenge to design and build an 1.1L single super charged methanol feeded engine that should produce 250 ish hp at 10000+ rpm. Lot of heat and forces (also for the dyno of that hammering torque). Also for balancing the 1st and 2nd order forces there has to be large balance shafts that could handle that rpm. Maybe it was better to design a 2 cylinder boxer for that purpose (but than you have two variables). I would like to put that engine in a 500 hp 2CV! So far it was pure theoretical design.



So far I know they use for inline 4 cylinder (with 180 deg. crank not cross plane) two 2nd order balance shafts for the outward movement of the connecting rod and weight of pistons. One rotate the same direction as crank, other (same axial spacing) rotate opposite direction.

I was wondering about the balance shaft of that Ford/Saab V4. I saw that it is direct gear driven from the crank. Same dimension as crank gear and so rotate other direction than crank. Two weights on each side (180 deg. twisted). I don't know crank angle spacing of that engine (90 deg.?). It could be balancing primary forces or primary rocking motion (moment momentum)?



@admiral cool! I never have seen a R5 before. I see that these R5 engines produce more torque at even a lower rpm than a 1976 for example RD350. R5 36 hp 7000 rpm 38 Nm 6500 rpm and RD350C 39 hp 7500 rpm 33Nm 7000 rpm. They run on same carbs. I was thinking the go port membrane induction for what says on the side covers "torque induction". Port timing and port sizes etc might changed I see both have 5 ports.

The RD is still my first roadbike. Original it came from Germany, and so a German RD250C from 1976. Before year model C they had to modified the A and B models to reduce the power output to 27 hp. I read they have put larger exhaust headers than for example USA models. From 1976 they all produce 27 hp. In German you don't see a lot of 350, but mainly 250 because of this 27 hp, insurance technically cheaper (?)
Also the difference between German and not German 250C is that it have disc brake at front and rear. And a way larger rear light. These old days rear brakes are not the best. But with some modifications (steel lines, smaller master cylinders) the brake okay and more feedback. Tested the bike on the mountains this year, it is okay!
My dad have still a XT500 and learned riding on that bike. Yeah I do remember about riding with drums ;0 And liked the shaking of that engine! Whole front wheel moves when you stand at a traffic light.

Offline Admiral_dk

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Re: Big stroke 55 cc one cylinder ICE
« Reply #95 on: September 26, 2022, 08:27:09 PM »
I think you all oversaw the fact that I questioned two Balancers running @ Crank-speed/RPM ....  ;)

All the examples you gave are Balancers running @ Double Speed/RPM of the Crank .... (Second-Order).

I have a few Single Cylinder Engines (LS650 & DR350) in my possesion, with one Balancer and Yes - they are all (Spur-) Geared (with shock-couplings) directly to the Crank => Opposite rotation, with minimum extra Vibrations from the coupling medium. So an almost perfect First-Order Balance - just a small Rocking-Couple, as the point in the middle between the Crank and Balancer normally never is on the centerline of the Cylinder ....

R5F - Except that mine was Black & Silver-Grey-Metalic - this is the paint scheme :
http://www.pfeffer.ch/bilderr5.htm



Per

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #96 on: September 27, 2022, 06:06:18 PM »
True! In theory one balance shaft direct under the centreline of crank/piston would do the job. And indeed you can ask your self what rocking couple should do on this scale model engine. But for double the balance mass there is my crankcase no place for a two times thicker balance weight or larger diameter. So would go with two!
Shock coupling is a great idea. I think, if spur gears are metal. They will also introduce a little bit of vibrations. Maybe POM gears would take care of that.

Great model to see. I was fun if Yamaha did build there twins with rotary inlet!

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #97 on: December 02, 2022, 07:19:00 PM »
I would continue this balancing and oiling and other upgrades later. So I can fully focus on this project when I have the hobby time for it. I have already some nice ideas of using laser cut stainless steel sheet parts of making a secondary oil pan for dry-sump application. And use of hole / sweep cut out of sheets and press them together to make cooling channels for cylinder. Why not, just test it. Engine is already heavy!

Currently I am busy with building a mechanical geared clock as a gift for my grandfather! And need a quit a bit of programming and electrical designing.

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #98 on: May 04, 2023, 11:06:14 PM »
After a idea of a co-worker.

3D printed a Toroidal Propeller and fitted on the crankshaft. Just one from Grabcad.com, 200 mm diameter very thin layers.

Does it work? Check it out!

<a href="https://www.youtube.com/watch?v=vSVXlWPtbkc" target="_blank">http://www.youtube.com/watch?v=vSVXlWPtbkc</a>

Cheers

Found out that engine need larger jet.

Offline Kim

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Re: Big stroke 55 cc one cylinder ICE
« Reply #99 on: May 04, 2023, 11:33:40 PM »
That's pretty dramatic!

Seems like it might need to be a bit thicker maybe? :)

Kim

Offline Roger B

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Re: Big stroke 55 cc one cylinder ICE
« Reply #100 on: May 05, 2023, 08:22:37 AM »
Oooops  :o

A bit of vibration as well  ::)
Best regards

Roger

Offline Admiral_dk

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Re: Big stroke 55 cc one cylinder ICE
« Reply #101 on: May 05, 2023, 10:57:55 AM »
Engine runs fine  :ThumbsUp:

.... but have a look at the video just before you destroy the Prop and see how much it flexes - no way it can be used for this engine ....
It needs to be much bigger for flywheel effect and structual having blades that are much much more substatial + made in wood, metal or solid plastic ...!!!
I can't see a 3D printed (of the kind we have @ home) make one that isn't dangerous ....

Per            :cheers:

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #102 on: May 05, 2023, 05:18:48 PM »
Yes haha I also didn't expect the propeller to stay intact.
Maybe drawing on my own a Toroidal, but stiffer. And tune the printer on my own material (material here on work with these setting is better , now the layers did not melt together).
Or printing a turbine prop. But indeed it is still printed material and not machined.

Maybe wood would be better. I don't know how large propeller I can put on when engine runs max 3000 ish rpm and let say 1 hp.

Yes engine need some serious improvements of oil leakage and new cylinder and adding mass to crankweb (with balance shafts). But for now more things to do around home.

Alex

Offline AlexS

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Re: Big stroke 55 cc one cylinder ICE
« Reply #103 on: May 08, 2023, 04:59:34 PM »
Well.. Just put a propeller on this engine.

After some search on the web. 18x8 should be on the smallest side of the 55cc engine. But engine has low compression. Only thing is that it is not a revving beast.

We will see. After building a proper test stand for this animal.

Offline Admiral_dk

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Re: Big stroke 55 cc one cylinder ICE
« Reply #104 on: May 08, 2023, 08:35:05 PM »
Quote
Only thing is that it is not a revving beast.

True and that goes for most of the Engine builds here on site ....

I immidiately noticed that you have a very restrictive exhaust system on the Engine in the video ....
But that is far from the only thing that has an influence on the revs and the power output.

Consider an IC Engine as an Air-Pump - how much can it Flow per Second and you have a decent idea about Power out. The highest amount of HP, I got from my Suzuki K50 in my youth was around 10-11 HP @ 10000 RPM and it only had a 'Static Compression Ration' (measured from where the Exhaust closes & up) around 4:1 - but it flowed perfectly .... So - No Kinks anywhere, or 'Jumps in Diameter' (can't be avoided between Cylinder and ports). Likewise sharp turns of the Gas are to be avoided too.

I used to put the system under the Watertap so I could see how well the Ports flowed - anything that didn't come out in a nice straight line, had encountered a problem.

Next - all the parts must be stiff (not bending) and accurately aligned - either parallel or perfect 90 degrees (Crank comes to mind in regard to the Cylinder) .... if not you either get too much Friction or maybe a broken engine sooner than later ....

Sorry for all my 'Ranting' - take what you can use from it and forget the rest  ;)     :cheers:

Per

 

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