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What is a reed case motor

Discussion in HPI Baja Engine and Exhaust forum, started by PACO.

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  #1  
Old 08-17-2006, 11:38 PM
PACO PACO is offline
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What is a reed case motor

Hey all-
What is a reed case engine? I notice they have way more power, how do they differ from regular engines? I am so confused!
Michael

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Old 08-18-2006, 12:20 AM
DarkSoul DarkSoul is offline
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So if you look at the picture you can see that the RC motor on the left has the intake tract in the cylinder itself, the Polini motor on the right has the intake tract in the case.

The advantages of a case reed induction motor is that you are able to have a much larger intake with the inclusion of a reed cage which "cylinder intake" motors do not have, so there is an issue in higher performance motors of slight blowback into the intake since there is no valve to close to hold it all in. Also the advantages of utilizing a reed cage are that with different stiffnesses of reeds, you can further alter the behavior of the motor i.e. stronger reeds (stiffer) will give better top end power at the expense of a little loss of low end power, and softer reeds will have the exact opposite effect.

The list is about 20 pages long of advantages to reed cage motors, the sylinder intake types work well, and we do have case intake cases for the RC style motors, but your looking at $300 for just the case (they are all billet cases). To get rid of the cylinder intake, you can either just cap it with the included little billet cap, or fill it with JB Weld, to get rid of the excess volume. we have used these with amazing results, just gotta figure out how to get it into the buggy.









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Old 08-18-2006, 08:33 AM
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Are these reed case motors as reliable a say a stock motor? Do you have to buuld an insane engine when you have a reed case motor?
Michael
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Old 08-18-2006, 03:24 PM
EarthSurfer EarthSurfer is offline
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I wonder if we can raise the gas tank to the roll cage, so the carb and filter will fit underneeth the tank. It looks like a possibility to me, but I have not had time to try it.

The engine can be just as reliable. The major difference is the rear transfer that can be put in the back of the cylinder. It is possible that the ring ends can snag the added transfer port. It's only happened to me twice (for the same customer also) out of like 20 or 30 engines I have built. The first time, I think was my fault. The second time makes me either want to move the transfer port, or relocate the piston ring locating pin. You don't have to do any porting, and it would be as reliable as a stocker, but you would only see gains pretty much in the low RPM power. My Ped racers have raced with these engines for the last two years, and we are not switching back. The reed cases above (Trevor Simpson cases) are my favorite way to build a RC type engine. The small bore cylinders and stock cranks rev to the moon (like about 20,000 RPM)--and the bigger bores with stroker cranks, have gobs of low end and mid range--but still rev pretty good (almost 18,000). Those RPM numbers come off a scooter, or small go cart (Go-Quad), and might be even higher in a RC car.
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Old 08-18-2006, 10:08 PM
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Woah-
Slow down guys. With a reed cage motor, the fuel and air enter through the case into the combustion chamber and there is a reed to stop the backpressure into the intake, right so far? With a normal motor the air and fuel enter directly into the combustion chamber and the piston seals the intake for combustion? Also it looks like the reed case motor is huge by comparison! What are the fitment issues associated with this setup?
Michael
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Old 08-19-2006, 11:12 AM
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The first motor in the set of pics is not for RCs, he was just showing you the case reed induction, when you scroll down you see the cases for the rc motor. Nobody has tried the fit yet, there might be a problem on the baja cause of the tank.
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Old 08-19-2006, 04:15 PM
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Quote:
Originally Posted by PACO
Woah-
Slow down guys. With a reed cage motor, the fuel and air enter through the case into the combustion chamber and there is a reed to stop the backpressure into the intake, right so far? With a normal motor the air and fuel enter directly into the combustion chamber and the piston seals the intake for combustion? Also it looks like the reed case motor is huge by comparison! What are the fitment issues associated with this setup?
Michael
The normal motor (the piston port engine), the fuel and air still go into the crank case first as the piston does it's up stroke. As far as I know, all two strokes work this way--even the nitros (which is a rotary valve intake system)

The biggest difference is, the reed will fill the crank case when ever the crank case can take it. It relies on the difference of pressure between the crank case and the pressure on the other side of the reed. It can also keep filling the crank case past that point of pressure differences because of the inertia of the air rushing into the engine still forcing it's way past the reeds. Typically, the intake on a reed engine is open for a full 360 deg of crank rotation. There are also waves in the crank case--kinda like a pipe--that can be taken advantage of with both styles of engine, with the right length intake tract in both engines.

The piston port uses the skirt of the piston to control the intake, and when it is closed, nothing more is getting in no matter what the pressure differences, or the inertia of the fresh air/fuel.

As a result, you get a wider spread of power with the reed valve, and with the fifth transfer port, we can get more power than is possible with the piston port design.

Some people may think that a reed valve will not let the engine rev as far as a piston port (because the reed valve is an obstruction), but I found I gained at least 1500 RPM (sometimes more) with any top end I put on the reed cases.
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Old 08-20-2006, 03:45 PM
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appears i need to break down the Boss 23cc which is a reed case motor designed for RC use from the ground up. i ll take pics of it as i tear it down and post them so people can get a good idea of differances.

Timmahh
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Old 08-22-2006, 03:29 AM
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ok, here are some pics of the Boss 23 motor for those inquireing minds. it seems i had something metal on top of the piston the was causeing my occasional ticking sounds i was hearing. no idea what. the piston was beat up but in relatively good shape. the top is knarwled up, and the bottom part ( engine is mounted on an angle for lower CoG) was pushed down and pinching the ring. going to see what the parts will cost, and see what i can mod in from stuff here in the states. cylinder is in good shape no marks. will maybe look at putting in a dome pistion, but i ll need to do a bit to touch up on the head to smooth it out some first. gonna see what the new parts run and go from there.
Timmahh

the engine and engine mount. how it sits in the car.


here is the differance between a reed case.


Reed Cage



my abused but repairable head. :?



piston abuse



a few pic of the porting inside the cylinder



wall are nice atleast! :wink:

im not sure What was on top, nothing loose came out when i pulled the head. going to pull the cluthc and the flywheel and the pull the case apart. may as well put in new bearings all the way with a new piston ring and wrist pin. need to check the size of the piston and see if there is a dome piston i can get in with a lil work.

hope this helps explain some of the main differances.
Timmahh
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Old 08-22-2006, 08:51 AM
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MAN!! That is one BAD looking motor!! Who makes that & why aren't they more available?? That has all the bells & whistles!!!
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Old 08-22-2006, 01:14 PM
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looks like the BOSS engine.

I mucked around with one on a dynamic F1, was well over 10 years old, still ran pretty good.
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Old 08-22-2006, 03:10 PM
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yep. Bergonzoni Boss 23cc. according the the Berg site, this motor ( the initial concept) was designed and manufactured totally in Italy, strictly for the rc world and for the Bergonzoni line of cars. they are rated at 3.5 hp @16,000 rpm stock i think it is.... and can be modded up from there. but being a reedcase motor, im not sure how well it would fit... i may at one point pull the fuelie out to see how much room there is, but assume i ll need to mod/move the gas tank a bit to get it in..

Jeep has one ( the whole car, a brave 2) hes looking to sell. if i had the money i d prolly get it. but i dont at the moment. maybe later if he still has it.
im eager to see how much parts will be. waiting on an email from Berg with prices.

Timmahh
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Old 08-22-2006, 08:26 PM
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Timmahh
Thanks for the pics and info, keep it comming, this helps alot.
Michael
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Old 08-23-2006, 05:32 AM
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someone at DDM or ESP can much better describe what is being seen, i can only get you the pics. lmao.. i have a decent mechanical knowledge of them, but not a working knowledge. that, i am building along with that motor you see in the pics.
i ve messed with small engines in the past, but never in this extent.
Timmahh
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Old 08-23-2006, 09:12 AM
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Quote:
Originally Posted by Timmahh
someone at DDM or ESP can much better describe what is being seen, i can only get you the pics. lmao.. i have a decent mechanical knowledge of them, but not a working knowledge. that, i am building along with that motor you see in the pics.
i ve messed with small engines in the past, but never in this extent.
Timmahh
Something either got in the engine, or came apart in the engine (check all bearings and bearing cages)---and totally beat the dog poop out of your piston and squish band, before whatever it is blew out the exhaust. Check the exhaust can/pipe---whatever it was, may still be in there.
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Old 08-23-2006, 03:03 PM
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yea, havent found anything yet.

Quote:
someone at DDM or ESP can much better describe what is being seen
< i was speaking of the ports and the function of the reed case.
and the squish band? this term totally loses me. when i hear squish band, i think of a really crappy bar band that got beers tossed on them then got stomped good out in the parking lot. so now they re a squish band..lmao..l

i knew something was beating the hell outta it, and im really surpised the cylinder walls are clean with the amount of beating the head/piston took. exhaust and the rest of the parts are clear. and nothing loose has fallen out yet. i still need to pull the flywheel and clutch to pop the case open to check the bearing in the case n crank. will do that in the next few days.

all i need to do now is find parts so i can put it back together.
Timmahh
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Old 08-23-2006, 03:09 PM
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It was probably intermittant because it would lodge itself into the piston, then break loose & do damage, then lodge itself for a while. JMO from the way it looks.
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Old 08-23-2006, 04:50 PM
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Could possibly be part of the spark plug that did the damage also.

The squish band (A one--A two--A one , two, three----duuuuccckk!!) Timmahh is that ring with all the damage on it on the head. It's job is to squish the fresh fuel air closer to the spark plug when the piston gets close to the top of it's stroke.
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Old 08-23-2006, 06:05 PM
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A little clarification, the "squish" or "squish band" is generally a reference to the amount of space from the top of the piston crown ("A" in the pic) to the cylinder dome ("B" in the pics) at TDC (top dead center) measured, usually, in millimeters, usually around .5mm to .7mm.

The beat up parts of that motor it looks like is from either a broken fragment of one of the piston rings, or the electrode of the spark plug having fallen out. Regardless of what did the damage, the entire motor needs to be torn down and rebuilt. New cylinder (that one is beyond repair unless you send it to Millenium Ent. but they would charge probably more than it is worth), new piston, and all new bearings. Also the case should be inspected, if the fragments got into the case, its possible that they damaged both the crank and the case by tumbling around in there.

*Also a quick bit of info on compression, compression is maintained by two factors. 1. is the size of the "squish chamber", the smaller dome in the top of the cylinder where the sparkplug protrudes into the cylinder, and the "squish, or squish band". Regardless of what the volume of the squish chamber, the squish band, should always allow for expansion and contraction of the metal components as well as stresses and material fatigue that is inherent to a reciprocating motor spinning at upwards of 18000 rpm. The broad strokes "rules of performance" in regards to squish band height is the larger the number (lets say .8mm) the more top end you will be able to achieve, with a small penalty in bottom end grunt, and the tighter the squish (we'll call it .4mm) the better your bottom end grunt will be, but the tighter it gets the more chance there is for a catastrophic failure as well as increased heat build up.





Hope you guys found this helpful, and not too boring :roll:
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Old 08-23-2006, 07:55 PM
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got it. basically the squish or squish band is the volume of open area above the very edge of the piston while at TDC, and the area just about it on the head. check.

so the bigger the squish band, the more torque you ll get, the smaller the squishband the more top end you ll get, with a small trade off on the other side. ie. more rpm less torque and more torque less RPM or top speed.

this motor has one ring. and it was in great condition except for being pinched into the ring grove in the piston due to the edge of the piston that was being beat was compressed and holding the ring in place.. ofcourse i broke it trying to remove it, and chipped the top of the piston at the same time. no biggie, i planned on new piston and ring as soon as i seen it.
the sparkplug, A Bosch R10 was basically new looking when i pulled it out. no lost pieces parts. wrist pin bearings are all accounted for. nothing in the exhaust or in the case. still need to pull the case apart to look imside and inspect for any damages... what ever it was was SMALL, cuz it never stopped the motor from starting or running, but occasionally would tick for a few seconds then go away. it took a few times before i realized it was in the engine, not the cluth area or ps area like i had originally thought. of course too late.

DS, can you explain the need for the new cylinder or work that needs to be done to it, as the cylinder to me looks great. no marks mares, nics, scratches at all, which did surprise me considering the amount of beating on the piston and head. or were you refering to the head?

i emailed Daniele at Bergonzoni with questions on parts and prices. no reply yet. basically im looking to buy a full set of bearings for the entire engine, crank, rod, wristpin ect.... all gaskets, a new piston, ring, and wrist pin, or gougeon shaft i think it is also called, as well as a new carb for the shelf. it seems walbro made the WT-524 specifically for the Berg engines. no one else carries this perticular carb that i can find here in the states....

if anyone overseas has info to get parts from the Bergonzoni in Italy, or any UK supplier or the like, could you please post up. i would really like to get this put back together this fall so i can do some running before the snow flies in November. and replys from Berg has been slow....

Thianx for the Education Peeps. YOU GUYS ROCK with your willingness to impart your vauluble knowledge on us.

i have a few 25cc engines i may play with the dremel on. need to do a bit more reading and educating myself on porting and the dos and donts. a bit more and i ll be ready to fugg up my first port job on this old beat up 25 cc weedwacker i got here.

THANX
Timmahh
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