RE: Simple Method To Find T.D.C. (top dead center)

RE: Simple Method To Find T.D.C. (top dead center) (Full Version)

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1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/16/2011 2:19 PM)
Earl - do you have a link to where you found these quotes and pictures from? I'd be curious to see the other side of those brass liners... mainly the fox liner. It seems the Fox liner is all "snazzed up" with the fancy port shapes and the Rossi looks like a regular old 3-port sleeve. (or what I would call "regular looking" anyway, timing aside) For the historical part, I've been getting Estate Sale information for awhile now in hopes of finding a modelers collection up for sale.. I see a few guys picking up boxes of old engines from estate sales or garage sales every now and then, just not around my neck of the woods it seems.

earlwb -> RE: Simple Method To Find T.D.C. (top dead center) (7/16/2011 2:31 PM)
It was back in that huge Fox engine thread we have here, Konrad was discussing how Fox had to go overboard to get his Quickie engine to outperform the Rossi engine. I had not figured out how to get a link to a specific page so the URL reference didn't work like I wanted at the time. i don't remember seeing pics of the other side though. The OS engines pics were from a thread where they were discussing tuned pipes and how to get the most from the engines at the time. It was around here http://www.rcuniverse.com/forum/m_3354294/mpage_73/printable.htm I had saved the pics and re-posted them instead of looking for the original threads. I have his email address, I'll ask him if he has any more pics of the Fox Quickie and Rossi liners. Now then the Rossi engine used a larger crankshaft wheras the Fox engine had a smaller crankshaft. So Fox had to be more radical in trying to get the engine to breathe better.

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/16/2011 2:57 PM)
quote: ORIGINAL: earlwb It was back in that huge Fox engine thread we have here, Konrad was discussing how Fox had to go overboard to get his Quickie engine to outperform the Rossi engine. I had not figured out how to get a link to a specific page so the URL reference didn't work like I wanted at the time. i don't remember seeing pics of the other side though. The OS engines pics were from a thread where they were discussing tuned pipes and how to get the most from the engines at the time. It was around here http://www.rcuniverse.com/forum/m_3354294/mpage_73/printable.htm I had saved the pics and re-posted them instead of looking for the original threads. I have his email address, I'll ask him if he has any more pics of the Fox Quickie and Rossi liners. Now then the Rossi engine used a larger crankshaft wheras the Fox engine had a smaller crankshaft. So Fox had to be more radical in trying to get the engine to breathe better. Good info, Earl. Thank you. Is it me or has Konrad not been around lately?

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/16/2011 3:53 PM)
Okay.. I degreed the Sportster .65, here is what I came up with... Exhaust open 70° BBDC close 111° BTDC Transfers open 123° BBDC (boost port opens and closes at the same time as transfers) close 125° BTDC Crank open 140° BTDC close 42° ATDC Blowdown period 11° So if my math is reasonably close, The exhaust duration is 221°, Transfer duration 112°, and crank/intake 182°. Sound about right? edit: added blowdown timing

earlwb -> RE: Simple Method To Find T.D.C. (top dead center) (7/16/2011 4:25 PM)
quote: ORIGINAL: 1QwkSport2.5r quote: ORIGINAL: earlwb It was back in that huge Fox engine thread we have here, Konrad was discussing how Fox had to go overboard to get his Quickie engine to outperform the Rossi engine. I had not figured out how to get a link to a specific page so the URL reference didn't work like I wanted at the time. i don't remember seeing pics of the other side though. The OS engines pics were from a thread where they were discussing tuned pipes and how to get the most from the engines at the time. It was around here http://www.rcuniverse.com/forum/m_3354294/mpage_73/printable.htm I had saved the pics and re-posted them instead of looking for the original threads. I have his email address, I'll ask him if he has any more pics of the Fox Quickie and Rossi liners. Now then the Rossi engine used a larger crankshaft wheras the Fox engine had a smaller crankshaft. So Fox had to be more radical in trying to get the engine to breathe better. Good info, Earl. Thank you. Is it me or has Konrad not been around lately? I think he got banned for a while. I don't know but Google sometimes frustrates me. I do a search for something one time and I get a bunch of hits, then later when I do it again the hits are all different and I can't find the link i was looking for that was there the first time.

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/16/2011 4:33 PM)
quote: ORIGINAL: earlwb quote: ORIGINAL: 1QwkSport2.5r quote: ORIGINAL: earlwb It was back in that huge Fox engine thread we have here, Konrad was discussing how Fox had to go overboard to get his Quickie engine to outperform the Rossi engine. I had not figured out how to get a link to a specific page so the URL reference didn't work like I wanted at the time. i don't remember seeing pics of the other side though. The OS engines pics were from a thread where they were discussing tuned pipes and how to get the most from the engines at the time. It was around here http://www.rcuniverse.com/forum/m_3354294/mpage_73/printable.htm I had saved the pics and re-posted them instead of looking for the original threads. I have his email address, I'll ask him if he has any more pics of the Fox Quickie and Rossi liners. Now then the Rossi engine used a larger crankshaft wheras the Fox engine had a smaller crankshaft. So Fox had to be more radical in trying to get the engine to breathe better. Good info, Earl. Thank you. Is it me or has Konrad not been around lately? I think he got banned for a while. I don't know but Google sometimes frustrates me. I do a search for something one time and I get a bunch of hits, then later when I do it again the hits are all different and I can't find the link i was looking for that was there the first time. I see.. I thought it odd I hadnt seen him posting for awhile but I do remember some threads getting pretty wild.. I know how the google thing goes.. I'll come across stuff I want to go back and find and of course forget to bookmark it and can't ever find it again..

earlwb -> RE: Simple Method To Find T.D.C. (top dead center) (7/17/2011 12:05 AM)
I had totally forgotten about it. but the Rossi dealer has some nice photos of the Rossi engine cylinders and crankshaft even, showing the stock cylinder and the special modified cylinders and crankshaft that one can get for the engines. Yes there are 3 port and 5 port cylinders and the 5 port offers a little more performance of course. But the cylinders do look that way on the Rossi engines. They have a large crankshaft with a larger center hole or port for flowing the air/fuel mixture into the crankcase, which is how they were able to run so good without having to make the cylinder ports too large. http://shop.vendio.com/RossiEnginesUSA/item/2039499748/index.html The special modified VP cylinders show some of the special airflow smoothing and improvements done to reduce turbulence, including the camfering and cutouts on the crankshaft too. Anyway this is a good example of some tuning and performance techniques one can do to the engines. The VP modified crankshaft is on the left as well as the VP cylinder. Note they did the cutouts on the crank as well as streamlined it to reduce turbulence and they bead blasted it to reduce surface stresses too.

earlwb -> RE: Simple Method To Find T.D.C. (top dead center) (7/17/2011 12:10 AM)
One final thought is that a couple of guys have emailed me stating that it is dangerous to mess around with dremeling or filing on cylinders that are nickel plated as people have developed allergic reactions to it, and some have gone into anaphylactic shock even. Even if you wear a air filter you could have contact dermatitis from it too. For example: ref http://www.aocd.org/skin/dermatologic_diseases/nickel_allergy.html and http://www.ptca.org/forumtopics/topic_metal_allergy.html

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/17/2011 1:13 AM)
quote: ORIGINAL: earlwb One final thought is that a couple of guys have emailed me stating that it is dangerous to mess around with dremeling or filing on cylinders that are nickel plated as people have developed allergic reactions to it, and some have gone into anaphylactic shock even. Even if you wear a air filter you could have contact dermatitis from it too. For example: ref http://www.aocd.org/skin/dermatologic_diseases/nickel_allergy.html and http://www.ptca.org/forumtopics/topic_metal_allergy.html I really didnt have any intention of modifying a nickel plated sleeve for fear it would peel. If I do any mods to my TT .46, it will be to the crankshaft only. The sleeve and piston I will leave alone. Those port cutouts in the modified sleeve is what I've done to car engines in the past. There is a noticeable difference in performance, but its not night and day though.

downunder -> RE: Simple Method To Find T.D.C. (top dead center) (7/17/2011 1:18 AM)
quote: ORIGINAL: 1QwkSport2.5r Okay.. I degreed the Sportster .65, here is what I came up with... Exhaust open 70° BBDC close 111° BTDC Transfers open 123° BBDC (boost port opens and closes at the same time as transfers) close 125° BTDC Crank open 140° BTDC close 42° ATDC Blowdown period 11° I find it much easier to relate the cylinder timings around BDC so your exhaust timing would show as opening at 70 BBDC and closing at 69 ABDC then simply adding the two figures together gives the total open duration of 139 degrees. I'm not sure how you arrived at 221 degrees. The transfer opening figure was a typo :) and should have read ATDC, not BBDC, but converting it would make the opening as 57 BBDC. Subtracting the 57 from the exhaust opening of 70 gives a blowdown of 13 degrees. These figures are quite typical for an engine designed to swing large props by developing high torque at lowish revs (and would probably make a fairly decent CL stunt engine :)). The crankshaft timing is identical to a Merco 61. One thing that has me curious (and needs to be double checked whenever you see it) is that normally the port timings are completely symmetrical around BDC. Your figures show a difference of 1 or 2 degrees between the opening and closing times. This can happen if your pointer is off by a degree or so when set for TDC but occasionally you'll run across an engine that has a Desaxe arrangement where the crankshaft is offset very slightly from the centreline of the cylinder. All Mercos are like this as is the SC 108 and Fox 35 (and possibly other Foxes as well). About the only way to tell if an engine really does have a Desaxe arrangement is to push the piston firmly down to BDC then look through the back of the engine at the alignment of the rod to the crankshaft port. If it's slightly offset so that more of the port shows past one side of the rod then it's Desaxe.

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/17/2011 1:52 AM)
quote: ORIGINAL: downunder quote: ORIGINAL: 1QwkSport2.5r Okay.. I degreed the Sportster .65, here is what I came up with... Exhaust open 70° BBDC close 111° BTDC Transfers open 123° BBDC (boost port opens and closes at the same time as transfers) close 125° BTDC Crank open 140° BTDC close 42° ATDC Blowdown period 11° I find it much easier to relate the cylinder timings around BDC so your exhaust timing would show as opening at 70 BBDC and closing at 69 ABDC then simply adding the two figures together gives the total open duration of 139 degrees. I'm not sure how you arrived at 221 degrees. The transfer opening figure was a typo :) and should have read ATDC, not BBDC, but converting it would make the opening as 57 BBDC. Subtracting the 57 from the exhaust opening of 70 gives a blowdown of 13 degrees. These figures are quite typical for an engine designed to swing large props by developing high torque at lowish revs (and would probably make a fairly decent CL stunt engine :)). The crankshaft timing is identical to a Merco 61. One thing that has me curious (and needs to be double checked whenever you see it) is that normally the port timings are completely symmetrical around BDC. Your figures show a difference of 1 or 2 degrees between the opening and closing times. This can happen if your pointer is off by a degree or so when set for TDC but occasionally you'll run across an engine that has a Desaxe arrangement where the crankshaft is offset very slightly from the centreline of the cylinder. All Mercos are like this as is the SC 108 and Fox 35 (and possibly other Foxes as well). About the only way to tell if an engine really does have a Desaxe arrangement is to push the piston firmly down to BDC then look through the back of the engine at the alignment of the rod to the crankshaft port. If it's slightly offset so that more of the port shows past one side of the rod then it's Desaxe. I'll re-degree the engine. My pointer may have been off a degree plus the wheel I was using was numbered a little differently than the wheel w8ye posted. The reason my numbers were a little goofy is because the wheel was numbered goofy. I'll re-do it and see if I get similar numbers to what you converted for me.

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/17/2011 4:07 PM)
Alright, downunder... I think I got this... maybe.. On my degree wheel, it is already split into 4 quadrants of 90° each. I labelled them as ATDC, BBDC, ABDC, and BTDC respectively. This makes better sense to me, also gives small numbers which the other wheel doesnt. So... I remeasured my lugger .65. Starting at TDC rotating in normal engine rotation I get: Exhaust opens at 71 BBDC closes at 68 ABDC. Transfers and Boost open at 63 BBDC and close at 56 ABDC Crank opens at 40 ABDC and closes at 40 ATDC So that should mean a blowdown period of 8°. I sharpened the pointer, and used the light a little differently to get more accurate results. Hoping this sounds right. I think I got the abbreviations right too..

downunder -> RE: Simple Method To Find T.D.C. (top dead center) (7/18/2011 4:24 AM)
It's certainly starting to look as though the K&B has a Desaxe crankshaft although I'm a bit thrown off by the 3 degree difference with the exhaust and a 7 degree difference with the transfers because they should be pretty near exactly the same difference. One thing I do though is to get the opening time by moving the piston upwards so the conrod is loaded the same way as it is when the engine is running to take up the clearances at both ends of the rod. The closing times turning the crank in the normal direction is fine because then the rod is still loaded as it is when running. When I check the exhaust I have the head off and a strong light shining down the bore. I look a little upwards through the exhaust port as the piston moves up until there's just the barest glimmer of light at the top edge of the port. The transfers are a bit harder to do because there's no way to illuminate them so I like to do them in sunlight looking down the bore. I turn the crank slowly while watching the top edge of the port until it just disappears or suddenly gets covered by an oil film. I use the oil film trick too with the crankshaft and also in sunlight. The opening time is found by turning the crank backwards (closing the port) until I see an oil film along the length of the port. Same for the closing time except turning the crank in the normal direction. For each reading I'll repeat it 4 or 5 times to make sure it's consistent. This is the setup I use for timings. It's just a 360 degree plastic protractor with a bit of soft wire for a pointer I can bend to get fine adjustment for TDC.

iskandar taib -> RE: Simple Method To Find T.D.C. (top dead center) (7/18/2011 3:42 PM)
quote: ORIGINAL: downunder-RCU For sure this is the most accurate way to find TDC..the hard part is finding a 1/4x32 screw to fit the plug threads :) Try removing the coil from an old glow plug and gluing in a close fitting drill end or similar to act as a stop, but round off the end. Aim to have the piston contact at somewhere around 10 degrees either side of TDC but before you get any ABC pinch. How about this? [:D] http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11049 [image]http://www.hobbyking.com/hobbyking/store/catalog/S620.jpg[/image] Iskandar

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/18/2011 3:56 PM)
quote: ORIGINAL: downunder It's certainly starting to look as though the K&B has a Desaxe crankshaft although I'm a bit thrown off by the 3 degree difference with the exhaust and a 7 degree difference with the transfers because they should be pretty near exactly the same difference. One thing I do though is to get the opening time by moving the piston upwards so the conrod is loaded the same way as it is when the engine is running to take up the clearances at both ends of the rod. The closing times turning the crank in the normal direction is fine because then the rod is still loaded as it is when running. When I check the exhaust I have the head off and a strong light shining down the bore. I look a little upwards through the exhaust port as the piston moves up until there's just the barest glimmer of light at the top edge of the port. The transfers are a bit harder to do because there's no way to illuminate them so I like to do them in sunlight looking down the bore. I turn the crank slowly while watching the top edge of the port until it just disappears or suddenly gets covered by an oil film. I use the oil film trick too with the crankshaft and also in sunlight. The opening time is found by turning the crank backwards (closing the port) until I see an oil film along the length of the port. Same for the closing time except turning the crank in the normal direction. For each reading I'll repeat it 4 or 5 times to make sure it's consistent. This is the setup I use for timings. It's just a 360 degree plastic protractor with a bit of soft wire for a pointer I can bend to get fine adjustment for TDC. My numbers should be accurate to within 2 degrees provided my wheel is right on. I'm goin to buy a protractor today to be more definitive. I has the head, backplate, carb, and exhaust off the engine. (the engine being measured has never ran). I used a halogen work light to shine into the exhaust and backplate area. I took my measurements from the exact point I could see light showing through the port as the port opened and closed. The piston to bore tolerance is not real tight at the bottom of the bore so I may have seen a glimmer of light between the piston and bore but again, the discrepancy should be within 1 or 2 degrees. I will look into the desaxe timing thing when I have time after work. At BDC, the conrod covers the crank outlet almost completely. Not sure if it matters, but there is a divider in the middle of the transfer ports and the transfer on the rear of the engine is almost useless as the backplate is not recessed to aid in fuel flow over the backplate. After getting a protractor, I'll double check my measurements to verify a desaxe port configuration. Also to note, the engine has been mounted rigid in my test stand so the engine and pointer stay in one place for more accurate measurements. What engine is in our sons car, if it's a Traxxas 3.3 I should measure mine and compare to your numbers to check my accuracy. I already measured a 2.5 but I didn't want to pull my fresh 3.3 apart just yet. Maybe I will to verify I'm measuring this right.

earlwb -> RE: Simple Method To Find T.D.C. (top dead center) (7/18/2011 4:20 PM)
quote: ORIGINAL: iskandar taib quote: ORIGINAL: downunder-RCU For sure this is the most accurate way to find TDC..the hard part is finding a 1/4x32 screw to fit the plug threads :) Try removing the coil from an old glow plug and gluing in a close fitting drill end or similar to act as a stop, but round off the end. Aim to have the piston contact at somewhere around 10 degrees either side of TDC but before you get any ABC pinch. How about this? [:D] http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11049 Iskandar They do sell 1/4x32 taps and dies. One can thread a length of brass or aluminum rod to make a longer screw as needed. Here is a ebay search for some examples: http://shop.ebay.com/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=1%2F4x32+die&_sacat=See-All-Categories One can also drill and tap a old glow plug out for a small size long screw too.

iskandar taib -> RE: Simple Method To Find T.D.C. (top dead center) (7/18/2011 5:35 PM)
On the other hand, the Hobbyking tool costs $1.19.... Incidentally, I was told of a great place for taps and dies: http://www.victornet.com/ They have 1/4x32 (normal glow plug), M8x0.75 (turbo plug) and 11/32x32 (Nelson plug) taps AND dies. Bottoming taps aren't available for everything, though. Prices are ultra-reasonable. Iskandar

earlwb -> RE: Simple Method To Find T.D.C. (top dead center) (7/18/2011 7:30 PM)

Thanks for the link, I had forgotten about them.
Now that has me wondering as to what one uses the really fine threaded 1/4 dies or taps for. Such as the 1/4x80 or the 1/4x72 dies shown below.

1/4-40 HS 1" OD Special Die	1/4"	40	1"
	$10.30	RD-1/4-48-B	1/4-48 HS 1" OD Special Die	1/4"	48	1"
	$10.30	RD-1/4-56-B	1/4-56 HS 1" OD Special Die	1/4"	56	1"
	$10.30	RD-1/4-60-B	1/4-60 HS 1" OD Special Die	1/4"	60	1"
	$10.30	RD-1/4-64-B	1/4-64 HS 1" OD Special Die	1/4"	64	1"
	$10.30	RD-1/4-72-B	1/4-72 HS 1" OD Special Die	1/4"	72	1"
	$10.30	RD-1/4-80-B	1/4-80 HS

iskandar taib -> RE: Simple Method To Find T.D.C. (top dead center) (7/19/2011 7:30 AM)
quote: ORIGINAL: earlwb Thanks for the link, I had forgotten about them. Now that has me wondering as to what one uses the really fine threaded 1/4 dies or taps for. Such as the 1/4x80 or the 1/4x72 dies shown below. If you were making ultraprecise micrometers, perhaps? Or length gauges? Iskandar

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/19/2011 10:56 PM)
quote: ORIGINAL: downunder It's certainly starting to look as though the K&B has a Desaxe crankshaft although I'm a bit thrown off by the 3 degree difference with the exhaust and a 7 degree difference with the transfers because they should be pretty near exactly the same difference. One thing I do though is to get the opening time by moving the piston upwards so the conrod is loaded the same way as it is when the engine is running to take up the clearances at both ends of the rod. The closing times turning the crank in the normal direction is fine because then the rod is still loaded as it is when running. When I check the exhaust I have the head off and a strong light shining down the bore. I look a little upwards through the exhaust port as the piston moves up until there's just the barest glimmer of light at the top edge of the port. The transfers are a bit harder to do because there's no way to illuminate them so I like to do them in sunlight looking down the bore. I turn the crank slowly while watching the top edge of the port until it just disappears or suddenly gets covered by an oil film. I use the oil film trick too with the crankshaft and also in sunlight. The opening time is found by turning the crank backwards (closing the port) until I see an oil film along the length of the port. Same for the closing time except turning the crank in the normal direction. For each reading I'll repeat it 4 or 5 times to make sure it's consistent. This is the setup I use for timings. It's just a 360 degree plastic protractor with a bit of soft wire for a pointer I can bend to get fine adjustment for TDC. Well, I bought a plastic protractor and compared it to my degree wheel. Other than the graduation lines being thicker every 10 degrees, its dead on to the protractor. I also stuck a piece of soft pine through the exhaust port to hold the rotating assembly at BDC. This is about as close as I can get to perfect BDC. 2 Pics of the crank to rod orientation in my K&B. It looks as though its offset slightly. [IMG]http://i153.photobucket.com/albums/s225/1QwkRusty2pt5R/IMG_0030-1.jpg[/IMG] [IMG]http://i153.photobucket.com/albums/s225/1QwkRusty2pt5R/IMG_0031-1.jpg[/IMG]

downunder -> RE: Simple Method To Find T.D.C. (top dead center) (7/20/2011 2:30 AM)
Yep, it sure seems to be offset (Desaxe), particularly the way the crank web doesn't line up the same with the engine mounts.

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/20/2011 2:59 AM)
quote: ORIGINAL: downunder Yep, it sure seems to be offset (Desaxe), particularly the way the crank web doesn't line up the same with the engine mounts. That was throwing me off because I hadn't heard of a desaxe crankshaft. I kept thinking the crank web should have been level. So my numbers make more sense? Does your son have a Traxxas engine in his car?

1QwkSport2.5r -> RE: Simple Method To Find T.D.C. (top dead center) (7/25/2011 2:22 AM)
I dug my old fox .40 out of the box of spare junk and timed it for the heck of it. This one is more symmetrical than my K&B.. Exhaust open at 74 bbdc, close at 75 abdc Transfers open at 59 bbdc, close at 60 abdc Boost open at 55 bbdc, close at 55 abdc Crank open at 40 abdc, close at 50 atdc Blowdown of 15° I'd guess this engine would turn somewhere around 13,000-14,000rpm or so?

iskandar taib -> RE: Simple Method To Find T.D.C. (top dead center) (7/25/2011 4:47 PM)
I used to carve up cheap RC sport engines and use them in Combat. Just retiming the crank did wonders, I didn't try raising the exhaust. My "usual" numbers for the crank were 35 degrees ABDC to 57 degrees ATDC (or sometimes 65). Very crudely measured - I scratched lines on a stiff piece of transparent plastic, lined up two crosshairs with the mold flashing and the bottom of the mounting lugs, lined up the middle of the crankpin with a marking, and scratch a line on the shaft. Then grind with a stone. OS engines had TOUGH cranks, Brats, Leos and Magnums were considerably softer. I'd run 7x6 Taipans on .28s and Scimitar 8x6s on .36s. Typically on 25% nitro. Always slower than a Nelson, of course - the Magnum .36 had a 12.5mm crank, the Nelson a whopping 17mm. The Magnum would be about as fast as an unmodified Mark IV, but it eventually spit the front of the crank out, along with the front bearing. Iskandar

downunder -> RE: Simple Method To Find T.D.C. (top dead center) (7/26/2011 3:47 AM)
quote: ORIGINAL: iskandar taib My ''usual'' numbers for the crank were 35 degrees ABDC to 57 degrees ATDC (or sometimes 65). Those figures are within a hair of the OS VF's (40,46 and 61) and close to an MDS 78 which is 32/52.

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