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Roots Type Supercharger

Old 09-03-2012, 11:56 AM
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Mike2735
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Default Roots Type Supercharger

Has anyone ever built a roots type supercharger for one of our gasoline engines? I just had a thought that it would be cool to do. I don't want to push too much boost but thought it might be something that would add some horsepower.

All comments welcome!!!!

Mike Moore
Nashville NC
Old 09-03-2012, 12:13 PM
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Jackal1983
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Default RE: Roots Type Supercharger

it would be cool but...
the amount of power you will use to run the charger... i think the advantangeof the boost will go!
Old 09-03-2012, 01:51 PM
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d-lo
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Default RE: Roots Type Supercharger

supercharging doesn't really work on two stroke engines, more of a four stroke thing. two strokes rely on drawing the air fuel mix through the crankcase, forcing it in with a supercharger would just force it through the exhaust port, not into the cylinder per say........... but if you are talking four stroke, then a mini turbo would be nice!
Old 09-03-2012, 04:11 PM
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Mike2735
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Default RE: Roots Type Supercharger

Thanks for the comments guys.

I was talking about a 2-stroke but I may have to look into a 4 stroke to see what is available.

I still may build an imitation one for my twin on my airboat just for the look!!
Old 09-03-2012, 05:33 PM
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Default RE: Roots Type Supercharger

We get (almost) free supercharging from the tuned pipe - it does not steal any power from the motor to make it work and provides considerable boost. There are plenty of supercharged 2 strokes (GM comes to mind) but the logistics of fuel management and the already mentioned loss of mixture out the exhaust would mean it would be more for show. But I am not sure there is a sound on this earth I like more than hearing a blower whining away on a boat - a mini version would be cool - even if not practical
Old 09-03-2012, 06:50 PM
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Mike2735
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Default RE: Roots Type Supercharger

This is my idea of what it might look like!!
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Old 09-03-2012, 11:50 PM
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Default RE: Roots Type Supercharger

I am going to open up a can of worms by saying this and it has been talked about more times than I can count, but our piston port engines can in fact gain from being boosted. The very thing that gives them that supercharged effect (tuned pipe) will also aid in holding back a fresh low boosted charge. Just how much boost depends on alot of different factors like pipe design exhaust port design, elevation the engine is running at, exhaust gas temps, etc... Without many hours of tuning and experimenting one would probally cause the engine to make less power than if it were normally aspirated. Some two stroke manufactors have gotten good gains by actually putting a valve inside the exhaust system. It is safe to say that a four stroke has way more to gain from a turbo or supercharger than a two stroke ever will. A boosted two stroke (turbo or supercharged) would also only show gains in a very small rpm range (when it is on the pipe) and would more than likely loose power when it is outside the powerband range- more so than stock

Justaddwatta- I have to agree with ya about the blower whine, there's a sound I could never get tired of listening too! Who needs a stereo system in their car or boat when you have a roots to play music for you!
Old 09-04-2012, 06:45 AM
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Mike2735
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Default RE: Roots Type Supercharger

Your replies have got me thinking. If there was a way to temporarily and extremely quickly to "block" the exhaust flow at the proper moment to allow some of the "boosted charge to remain in the combustion chamber until the piston clears the port. Would this work? I realize that this is also the time that the exhaust has to exit but if it were under "boost" then the exhaust gases would also exit more quickly. I have a few ideas on how to do this. I will do a drawing to see just how hard it will be, and let you guys know how it turns out.


Thanks for you replies.
Old 09-04-2012, 01:21 PM
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Jackal1983
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Default RE: Roots Type Supercharger

Im surprised nobody has designed a power valve engine yet!!!
hightening the exhaust port at higher rpm.
Old 09-04-2012, 01:49 PM
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Default RE: Roots Type Supercharger

Mike- The sound waves from the tuned pipe will help hold some of your boost in but I dont know how much boost you are shooting for? I can tell you this much, you would be far better off using a turbo as it is free power. A supercharger has to be turned by the engine itself and like Jackal said the extra power the blower would make would be used up by turning the blower. Jakcal, I am also just as surprised as you are about none of the smaller engine manufactors have not developed a version of a power valve. This would show huge gains across the board and it would also allow the user to adjust where his powerband starts and peaks without changing pipes. On the downside, it would add weight and bulk to the engine.
Old 09-04-2012, 06:54 PM
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Mike2735
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Default RE: Roots Type Supercharger

Hi all,

Thanks for more replies.

I do understand that it is at best a 50 50 proposition and that any gains would be used up by having to turn the supercharger with the engine, but gains are not the real reason I want to do this. It is the effect of seeing the blower on the engine as well as the "music" it will sing to you. If I could not lose anything in the process, to me that would be worth it. I really don't want to lose power.

I am in totally new territory for me. I have been in RC for a long time, and I am quite good at tuning both nitro and gasoline engines. But know what to do verses why it works are 2 totally different things. I know what to do but do not always know why it works. Like all of us I am still learning.

I will have my CNC up and operating in the near future and some of these things will be the first on the list that gets produced. I will have a lot of trial and error but that is where the fun is. What did someone say to Edison about how many prototypes he made before he made a working light bulb? Something like, It only took one to make it work but too how ever many to find out how not to do it. This is where I am and look forward to sharing my errors and successes with all of you.

Old 09-04-2012, 07:44 PM
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Default RE: Roots Type Supercharger

I understand your reasoning completly Mike... And You are more than welcome to pm me or even ask on here if you want more than one opinion. I have been working with 2 strokes for 28 years now from big detriot diesels to 25cc homelites and even our little nitro burners. I do not pretend to know everything about them as I am still learning new things everyday! There is no greater sound than the whine of a roots style blower, but I am afraid your two stroke tuned pipe might kinda drowned out the blower whine!! One thing to remember at wide open throttle and full boost it takes over 1,000 horsies just to turn the blower on a top fuel engine, now obviously if you tried to put that amount of boost to our little mills the cylinder would part ways with the block instantious- but what a show it would make!!
So what type engine are you planning on using and what kind of baseline boost are you shooting for? I have done some testing with running a valve in the exhaust system, so if you have any questions please ask!
Good luck Mike and have lots of fun!
Old 09-04-2012, 08:07 PM
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Mike2735
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Default RE: Roots Type Supercharger

8MILL - Love you handle. We need to talk because I have a Custom Gun business as well.

Back to the subject - I am planning on doing this on a 50cc Twin. I am not looking for a lot of boost, Only enough to maintain the power at the same level with the Super Charger, maybe a little more. I am mainly aiming for the look and sound. I have some Ideas about exhaust valving and will be Drawing them in Solidworks over the next few days. Thanks for the offer of your help. I am sure I will be needing it.

Off Subject. I will include a picture of my personal Rifle for you to admire...It is a 7MM STW on a Remington Action that has been completely blueprinted. It has a No. 9 Douglas Barrel. It has changed since this picture was taken. It now has a Proper Sniper Scope and a custom muzzle brake. It is deadly accurate. It only has a 5.2 inch drop at 500 yards with a 100 yard zero at 3440 FPS on my custom loads with a 140 grain bullet.

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Old 09-05-2012, 12:18 AM
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Default RE: Roots Type Supercharger

Mike, by the looks of things-(you like guns, you drive a chevy and you like to modify engines for your own reasons) I think we will get along just great!!! LoL....I have about 12 rifles and double that in handguns. I also do enjoy building my own rifles and handguns. I love long range shooting be it with a rifle or handgun (600 + for the rifles). A few of my favorites are a 6mm 284 wildcat, 22" barrel, bushmaster lower, nightforce NXS rectile. She is hard on barrels. Ive got a few rifles that my grandfather brought back from WWII that I have turned into benchrest rifles as well. 8mm Gewher sniper that has had alot of work done to it and is a sweet shooter. 6mm Lee Navy Rifle straight pull- if you know about rifles you know how rare these are! And He also brought me home a 8mm Lebel that has been cut down for French saddle gun, although I couldnt imagine shooting it from horseback as it would probally knock you off. The rifle is so light it has a brutal recoil, but very accurate for a French gun!! I reload for every firearm I own- it's just so much cheaper and the only way to get excellent accuracy at 600+ yards. That is a pretty impressive rifle you got there, pretty flat shooting for 7mm!

Anyways, Back on subject, I would love to see you SoildWorks drawings when they are finished! With a low pressure boost you might be able to get away with no exhaust valve!
Old 09-05-2012, 03:09 AM
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Default RE: Roots Type Supercharger

Guys - be great to see this thread back on topic.
Old 09-05-2012, 07:39 AM
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Default RE: Roots Type Supercharger

Your right, I apoligize!
Old 09-05-2012, 03:48 PM
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Default RE: Roots Type Supercharger

If you are going to go to the trouble of making a supercharger (a massive undertaking), why not try and fit it to one of the proprietry available four stroke engines that are around? Thinking one of the Honda GX series or similar.

If you are able to make a supercharger, then the engineering required to modify the engine to handle the supercharger would be a (relative) walk in the park.

I would like to see and hear one running.

Om the subject a few posts up on power valves, I do know of an experimental system in existance that alters the tuned pipe length on a slip coupling as revs increase, and I know the SAW runners use water injection at lower revs to fool the engine into thinking the pipe is longer to get a little more low end power to get the big props turning, the water is knocked off when the boat is moving fast to then simulate the shorter pipe and restore the tune for the max revs.

Good luck in whatever you do though.

Glenn
Old 09-05-2012, 06:22 PM
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Default RE: Roots Type Supercharger

already around common for nitro and 2 stroke one made in AU - I'll try and find their site

http://www.rbinnovations.com/category_s/3.htm


some 2 stroke info on 50cc

http://www.elsberg-tuning.dk/supercharging.html
Old 09-06-2012, 12:37 AM
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Default RE: Roots Type Supercharger


ORIGINAL: glennb2006

If you are going to go to the trouble of making a supercharger (a massive undertaking), why not try and fit it to one of the proprietry available four stroke engines that are around? Thinking one of the Honda GX series or similar.

If you are able to make a supercharger, then the engineering required to modify the engine to handle the supercharger would be a (relative) walk in the park.

I would like to see and hear one running.

Om the subject a few posts up on power valves, I do know of an experimental system in existance that alters the tuned pipe length on a slip coupling as revs increase, and I know the SAW runners use water injection at lower revs to fool the engine into thinking the pipe is longer to get a little more low end power to get the big props turning, the water is knocked off when the boat is moving fast to then simulate the shorter pipe and restore the tune for the max revs.

Good luck in whatever you do though.

Glenn
Glenn- I have seen simular done on nitro boats but without the water. Seen one that had a adjustable pipe, and a 3rd channel mixture control. Both the pipe and the mixture control workeed together, I am assuming as the turn would approach the pipe would lengthen and fatten the needle up for good power out of the turn then on the saw shorten the pipe and lean her down! I could see that being a nightmare to get setup and working right!
Old 09-06-2012, 12:45 AM
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Default RE: Roots Type Supercharger

Hey mike,
Glenn does make a good point about using a fourstroke- I almost mentioned it a few days back, but I read that you had already had the 50cc 2 stroke. I would be a breeze to boost a 4 stroke, but then again maybe you are looking for a challenge and that is why you want to go with a two stroke. I am interested in viewing your solidworks drawings. If you do some searching on google you will find others that have force fed two strokes with some sucess, but usally using turbos as they are free power.
Old 09-06-2012, 12:52 AM
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Default RE: Roots Type Supercharger

Mike,
I have quite a few larger sized end mills and lathe bits along with numerous other tool and die tools if you are interested? They are too big for my machines and I dont plan on ever getting larger machines.
Old 09-06-2012, 08:38 AM
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Mike2735
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Default RE: Roots Type Supercharger

Here is an exploded view of what I have planned. Let me know if you see anything wrong with my design. The rotors have a 120 degree twist like the Eaton supercharger. I don't know if this will work on such a small ap[lication.

Thanks.

Mike Moore
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Old 09-06-2012, 10:46 AM
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Jackal1983
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Default RE: Roots Type Supercharger

The problems with a roots blower is the tolerances have to be quite high for them to work well. Out of all the different types of charges the roots takes the most hp to run. The centrifugal one takes the least.. 

How do you plan to go richer when boost is applied? A welbro carb will go lean
Under boost that could be damaging. 

We ran water injection into a pipe on boat engines and it's very successful at fooling the sonic wave it's a shorter pipe than it actually is. 

Kind regards
Jack
Old 09-06-2012, 12:45 PM
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Mike2735
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Default RE: Roots Type Supercharger

Jackal1983 - I plan to install teflon strips on the edges of the rotors. This will help with the tolerance issue and with sealing. I also plan to add a "spray bar" in the system that will be dependent on available pressures that will spray more fuel as needed. I haven't completed the design for this yet but hopefully will have a drawing soon.

I also realize that a 4-stroke would be easier, But that is not the "look" that I want. And I realize that RBInovations has a centifugal type supercharger but this again is not the look I want. This is more about the look than the amount of boost I will get. I do want it to boost power and by doing this I may stumble across some solutions that have been a problem with supercharging 2 stroke engines. I am sure that I will have alot of problems to overcome.

Thanks for all you suggestions and comments. Please continue.

Mike Moore
Old 09-06-2012, 03:21 PM
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Default RE: Roots Type Supercharger

I totally get it Mike- I think your drawings look good, not too sure the gains of having a radical curve on your vanes would be worth all the trouble? The teflon wipers are a must! Looking good! You might be better off running an exhaust throttle on it, too soon to tell

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