flow ramps used for front intake engines

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Jim Allen

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Joined
Jun 7, 2005
Messages
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I will post photos & explanations concerning the machined phenolic flow ramps that are added to the crankshaft's intake track. They are secured with J-B weld after machining & final shaping. They help the engine to pipe up & give an extra 300 to 350 RPM on the high end. Small size, front intake engines, can produce more power than a similar size engine with a driven intake valve because there is no energy lost in driving the crankshaft's internal valve. The crankshaft in the lower left hand side of the photo shows what the ramp looks like after the J-B weld is applied.

Jim Allen
 
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Mike,

We tested several different radaii, some that were very long with a shallow raduis & others that were short with a greater radius. They all worked well, in a similar manner, therefore we concluded that what was important is not to have a abrupt angle for the incomming charge to strike as it enters the crankshaft's passage way. We stopped using the long shallow radius type ramps because they had to be formed with J-B weld & a telfon piece inserted into the crankshaft as a mold. The ramps we use now have the phenolic piece glued in place with J-B weld as a first step. We rough up the crankshaft area where the epoxy will contact the phenolic piece. Epoxy is applied to the phenolic piece's bottom side & it is inserted in the crankshaft while being held with a pointed Exacto knife blade. Any excess epoxy on the sides is remove with cotton swabs. A second step covers the phenolic piece with a thin layer of epoxy. Ramps made in this manner are very durable & remain in place for an indefinite period of time. Typical RPM increase of 300 to 350 RPM can be expected in our large ID (.750") crankshafts. The ramps also appear to increase the engine's ability to pipe up when the plane is launched.

Jim Allen
 
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Mike,

Are you still working with the toroidal head bottons on your nitro engines?

Jim
 
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I have received more questions concerning exactly how the flow ramps are installed using JB steel weld. Notice in the first photo how the inside of the gas passage way has been roughed up with two ball shaped carbide burrs. The larger size burr does the rear most area & the smaller burr does the remaining areas. When the roughed up area is finished it should look like the back side of the phenolic ramp piece, only larger in area. A rubber glove finger protector is worn when using the burrs because there are many very small sharp pieces produced. Notice that the phenolic pieces on the left have been sanded to a streamlined shape & test fitted before glueing. Notice the shape of the Exacto knife blade that is pushed into the phenolic piece to allow a thin layer of JB weld to be applied to the entire back side with a cotton swab. Cotton swabs are used to clean away any excess epoxy after the ramp pieces are pushed into place. Before the first glueing operation the inside of the crankshaft is cleaned with Sprayon layout dye remover. Before mixing the JB weld, the crankshafts are placed in a 250* F oven. Heating the crankshaft cause the JB weld to become very liquid which makes cleanup of any excess epoxy easy. An insulating glove is worn on one hand to hold the heated crankshaft.

A second operation will put a very thin layer of JB weld on the top of the pre-glued plenolic piece. This is done because the linen based phenolic material will absorb oil. The crankshaft is cleaned again with Sprayon & then heated again to 250* F for this operation which will make the JB weld flow to a smooth finish. I observe the finished pieces watching for any air bubbles that may form. The air bubbles are pricked with a very sharp, new Exactoe knife blade.

Jim Allen
 
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Samuel,

The crankshaft is going to be out of balance because the window is on one side. The ramp does not help this! Some manufacturers have moved the induction hole off center to compensate for some of the out of balance condition. We use a counter balanced prop driver (airplane engines) or a counter balanced flywheel (boat engines) to eliminate the out of balance condition. Both of these systems work very well. Failure to place the counter balanced pieces in the correct place will cause severe vibration & maybe crankshaft breakage!

The first photo shows the back side of a prop driver & a counterbalanced flywheel.

JA
 
Good to know. I'm assuming you index the flywheel so you know exactly where it's suppose to go.

Next question not to get off topic but how do you balance the new drum to the motor?
 
Yes. Both the flywheel (used on boat engines) & the prop driver (used on airplane engines) have an index mark & must be mounted properly. In your second question, are you refering to a drum valve or a bell valve used in which motor?
 
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There is no pratical method that can be used to balance the crankshaft (ramp or no ramp) of a front intake valve engine. This is because of the large size window that is required. The counter balance method we are using has been the best solution thus far.

JA
 
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Ever considered using a latex ramp that will flatten out at higher RPM? And conform to the inner crank?
 
Jim I stopped running the old short stroke motor cause I couldn't keep rods on bottom end... I have 2 of the new larger crank motors as well, but didn't get any better performance from the old motor. What bore on carburetor do you like on both motors?

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Alan,

I use the FAI long stroke engine on the HTB-360 tunnel hull. Notice that the engine has 4 mounting lugs on the crankcase & 2 on the front end. I use the OS Max 9-B, automatic fuel metering, high & low speed needles, 12 mm (.4724") bore carubretor, on this engine, with tuned pipe pressure. The silver bullet tuned pipe has a 5.000" long X 11/32" (.3438") ID stinger. Once the two needles are set properly, the engine has excellent throttle response from low to WOT. The Nelson heavy duty tapered seat plugs are used in the double hemi head. Typical RPM's in the 29,000 to 31,000 range with 65% nitro. No connecting rod problems in this engine or the pylon speed engines. An extra 5 ounces/ gal of Blendzall Racing Castor is added to the 65% Technology fuel. This same engine is also has an inboard set as shown in the first photo.

Jim Allen
 
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Samuel,

The crankshaft is going to be out of balance because the window is on one side. The ramp does not help this! Some manufacturers have moved the induction hole off center to compensate for some of the out of balance condition. We use a counter balanced prop driver (airplane engines) or a counter balanced flywheel (boat engines) to eliminate the out of balance condition. Both of these systems work very well. Failure to place the counter balanced pieces in the correct place will cause severe vibration & maybe crankshaft breakage!

The first photo shows the back side of a prop driver & a counterbalanced flywheel.

JA
Jim; How do you determine the correct places for the balancing holes in the flywheel ? J.
 
The first hole is placed 180* from the center of the window in the crankshaft. Two more holes were added on each side of the first hole & then two more were added on each side of the second pair. This gives a total of five holes. Two more smaller holes were added on each side to give a total of seven. The drill & test procedure gave us a very smooth running engine. A similiar thing was done to the propeller driver, except that it is a circular slot.

JA
 
Jim,

Does this take into account the weight of the rod and Piston or is it strictly the crank, flywheel, and collet balancing?
 
It is strictly the rotating mass of the crankshaft that is being considered. The fact that the engine runs very smooth, especially at WOT, tells us this is working. However, failure to place the indexed flywheel or propeller driver in it's correct position causes severe vibration & sometimes crankshaft breakage.The piston, wrist pin & the upper half of the connecting rod are partially balanced with the crankshaft's counter balance. It is impossible to fully balance a reciprocating mass with a rotating mass in any single cylinder engine. Also, the use of Ricardo's formula for balancing single cylinder engines which states that; the weight on the crankshaft's counter balance should equal the total reciprocating weight of the piston, wrist pin & upper half of the connecting rod plus 1/2 the total rotating weight of the bottom half of the connecting rod; cannot be used because of the high reciprocating weights found in our engines. 55% to 60% of the total weight of the piston, wrist pin & connecting rod works best in our engines operating in the 25,000 to 32,000 RPM range. Ricardo's formula is used in single cylinder engines that have hanger type pistons with intake windows in the piston's OD. There are no piston bosses in the normal places. Instead the small size piston bosses are fastened to the piston's crown. This makes the wrist pin very short in length. It also makes the connecting rod longer & reduces the rod's angle at 90*& 270*. The Kalfus engine is a example of this type of induction passage way.

Jim Allen
 
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