Scooterotica

Hi Sean,
........I notice that you are along similar lines with your crank shape to the old sixties Villiers one....which by the way apparently was notoriously weak and had twisting problems when handling any extra power....but as Dan says see what happens....don`t know if you don`t try?.... ....

I thought this may be of help....but if not never mind....at least you may be re-united with that Castrol R smell!....

quote....
"Both authors use Castrol R40 or Morris MLR40 at a ratio of 25:1 as a lubricant, not because they are traditionalists, but because it is the only oil they have found to cope with the rigours of racing a heavily tuned 197 or 250. They work well, even promoting the well being of a big end bearing that can have up to 2 thou wear, with no problems. The authors have seen other riders use synthetic oils at 40:1 with unsatisfactory results. Use of synthetic oils in modern liquid cooled motors is recommended, but not, please, in 30 year old motors."

As you have now decreased your primary compression, have you had thoughts about a more "ramming effect " from a more correctly designed inlet tract....or is space limiting?....and as now the transfers are more a storing space for the fuel, do you think the design of exhaust will be able to overcome that loss of compression?....

sean brady scooters wrote:Adspeed.........
consider this...........what if balance,and flow is increased ................?

Balancing is done with say plugs around the rod side which would indicate that in theory balancing means removal of material as you have. I can see this knife edging been ok in 4 stroke and certain other situations but still can't see how if will help anything else. Still open minded though.

What therory do ya have for a better/increased flow?

PS not meaningg to do ya head in just trying to get my head round it.

was there any workings out, what i mean is have you left enought metal to counter rod,piston+ pin etc. Or is it a case of suck it and see so to speak.

Leigh

Looking good Sean

Now that this has been done Can I now drop in the next problem to overcome which Im sure you will be looking at.

And that is the Exhaust...

So next on the agenda is what's you plans on exhaust.

As the RB exhaust will be tuned and designed for a higher Primary comp ratio with full crank.

But saying that the RB design inherentantly gives low Geo PCr due to large Inlet track and additional inlet/transfer ports, the amount of additional volume given by crank mods may not effect the exhaust action that much.... But it may

Basics to increase the negative pulse ie the sucking of the fuel up and out transfers etc. It's possible to get a stronger inverted wave by using a larger diffuser angle, but at the expense of wave duration.

Also remember if it doesnt perform as well as expected it could be the exhaust

So whats your thoughts

RinB wrote:
Now that this has been done Can I now drop in the next problem to overcome which Im sure you will be looking at.

And that is the Exhaust...

So next on the agenda is what's you plans on exhaust.

As the RB exhaust will be tuned and designed for a higher Primary comp ratio with full crank.

But saying that the RB design inherentantly gives low Geo PCr due to large Inlet track and additional inlet/transfer ports, the amount of additional volume given by crank mods may not effect the exhaust action that much.... But it may

Basics to increase the negative pulse ie the sucking of the fuel up and out transfers etc. It's possible to get a stronger inverted wave by using a larger diffuser angle, but at the expense of wave duration.

This was exactly my concern two post`s ago?.........

Maybe not quite so large tranfers would be adequate....but where do you start?....

I reckon we could speculate all day long about 'this aspect' and then 'that aspect' etc etc.....what about the exhaust, what about the size of the transfers, what about the weight of the rod and piston....what about the stars and the moon, etc etc.....all we've done is trim a few grams of the crank, its no big deal.

Have we lowered primary compersion THAT much....not really, a little bit....but not much. Also...when using the phrase 'low primary compresion' you really need to define what you mean by that......low compared to what?

As per Charlie Edmonds article in Scootering, Lambrettas are running way too high PC as standard anyway (did he quote 1.7 ??), and some modern motocross machines are down to 1.2....Jennings quotes 1.5 as a good figure in certain applications.....and thats my point.....trimming 40cc of the crank aint no big thing when it comes to HPC/LPC etc. RinB did the calc and it lowers PC by 0.07 ! Nuthin.

As stated, its experimental, and although its a lot of work....its rewards are expected to be small....but as with any tuning....a single small step is of no great consequence, but put that with 9 or 10 other small steps, and they all add up. And of course, don't forget, when tuning ANY machine, the first 70-80 percent of gains come relativly easily and cheaply.....but that last 20% is a bitch!

A change of reed petal thickness, a 2mm reduction of bellmouth tract, 1 mm off the top of the exhaust port, a couple of mm off the sides, decrease squish gap by 0.3 of a mm, decrease squish area by 10 perecnt, incease comp ratio by 15%, polish the exhaust port, upgrade the spark plug, increase the main jet size, change the front sprocket, trim 40cc off the crank, higher grade of oil, different oil/fuel mix %, higher octane fuel, a lighter piston, lighter flywheel, different cowl.....and on, and on....

Not one of these things alone is groundbreaking or revolutionary, nor will one single item have an earth-shattering WOW factor.....but as the list gets bigger, so does the accumlative effect on performance and reliability, and all we are doing with the crank.....is adding one more item to the list....another accumlative effect.

We expect it to help with performance due to a decrease in rotating mass, improved gass flow, reduced vibration, and give an increase in revs.....this is already the case on a similar set up......but we shall see, the proof is in the pudding. It'll be built in a couple of weeks and we'll see what 'dyno theory' says as well as real world performance, running and top speed etc.

If its s**t.....its s**t, i'll still sleep at night....but if it rocks, then its all cool.

So Guys, will you be doing a direct comparison between the modded crank and a full circle item when completed in the same dyno session to properly assess it?

The crank is a fine piece of work, and it would be really interesting to see how it does.

By the way, here's another crank mod that's been shot down on another (non-scootering) forum, but has impressive claims by it's developer (and patent holder).

They say:

The Parris Racing Concepts forced induction crankshaft modification works by cutting veins into the crank halves of the crankshaft. The veins are cut at specific angles into one crank half, and then a mirror image is cut into the other crank half. As the crankshaft spins, these veins pick up the fuel/oil mixture inside the crankcase. A process called flow dynamics then routes the fuel/oil mixture down the veins where it is directed at the transfer ports of the crankcase. When the engine enters its intake stroke, the extra fuel/oil mixture is pulled into the cylinder. The flow dynamics affect also atomizes the fuel/oil mixture in a way that allows a cleaner, more complete burn inside the combustion chamber.
The PRC forced induction crankshaft modification will work on any two stroke engine, i.e.; snowmobiles, dirt bikes, quads, jet skis, and even chainsaws. We modified a 2008 Suzuki RM250. It was found to gain 16.74% percent in HP and 18% in torque. Below is a comparative dyno showing the stock vs. mod results. The PRC modification produces enough torque that it has nearly eliminated the power band. A motor with a PRC, Inc. forced induction crankshaft pulls as hard all the way through the RPM range as a stock motor does once it hits its power band. Therefore, the modified machine gets to top speed faster than any stock machine currently available.

http://www.parrisracingconcepts.com/Home_Page.php

drunkmunkey6969 wrote:I reckon we could speculate all day long about 'this aspect' and then 'that aspect' etc etc.....what about the exhaust, what about the size of the transfers, what about the weight of the rod and piston....what about the stars and the moon, etc etc.....all we've done is trim a few grams of the crank, its no big deal.

Have we lowered primary compersion THAT much....not really, a little bit....but not much. Also...when using the phrase 'low primary compresion' you really need to define what you mean by that......low compared to what?

As per Charlie Edmonds article in Scootering, Lambrettas are running way too high PC as standard anyway (did he quote 1.7 ??), and some modern motocross machines are down to 1.2....Jennings quotes 1.5 as a good figure in certain applications.....and thats my point.....trimming 40cc of the crank aint no big thing when it comes to HPC/LPC etc. RinB did the calc and it lowers PC by 0.07 ! Nuthin.

As stated, its experimental, and although its a lot of work....its rewards are expected to be small....but as with any tuning....a single small step is of no great consequence, but put that with 9 or 10 other small steps, and they all add up. And of course, don't forget, when tuning ANY machine, the first 70-80 percent of gains come relativly easily and cheaply.....but that last 20% is a bitch!

A change of reed petal thickness, a 2mm reduction of bellmouth tract, 1 mm off the top of the exhaust port, a couple of mm off the sides, decrease squish gap by 0.3 of a mm, decrease squish area by 10 perecnt, incease comp ratio by 15%, polish the exhaust port, upgrade the spark plug, increase the main jet size, change the front sprocket, trim 40cc off the crank, higher grade of oil, different oil/fuel mix %, higher octane fuel, a lighter piston, lighter flywheel, different cowl.....and on, and on....

Not one of these things alone is groundbreaking or revolutionary, nor will one single item have an earth-shattering WOW factor.....but as the list gets bigger, so does the accumlative effect on performance and reliability, and all we are doing with the crank.....is adding one more item to the list....another accumlative effect.

We expect it to help with performance due to a decrease in rotating mass, improved gass flow, reduced vibration, and give an increase in revs.....this is already the case on a similar set up......but we shall see, the proof is in the pudding. It'll be built in a couple of weeks and we'll see what 'dyno theory' says as well as real world performance, running and top speed etc.

If its s**t.....its s**t, i'll still sleep at night....but if it rocks, then its all cool.

Looks as though you`ve covered everything then?........

156 D wrote:
Looks as though you`ve covered everything then?........

Not exactly - I did ask what the theory is behind this crank producing a better gas flow........?

just for interest........some other crank webs used for various things


What you see here are the crankshaft assemblies for small engines used on brush cutters, chainsaws, and, in particular, motorcycles. We also produce single-unit crankshafts used for outboard motors, compressors, and other such items.From 20cc brush cutters to chainsaws, motorcycles, outboard motors, and even 700cc snowmobiles, we produce the crankshaft assemblies.

No. Applications
1 Water vehicles
2 Motorcycles
3 Chainsaws
4 Brush cutters
5 Small-scale helicopters
6 Outboard motors
7 Compressors
8 Chainsaws
9 Motorcycles
10 Snowmobiles
11 4-wheel all-terrain vehicles
12 Snowmobiles
13 Blowers
14 Chainsaws