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I had a lot better look just now - with a pencil and paper - and it really makes no sense ....I assume (hopefully not Ass-U-Me) that it follows the Classic Beetle layout, with the inlets in the centre off the head and an exhaust at each end of it. In that case it's a Big Bang engine, where cylinder 1 and 4 fires simultaneously and likewise cylinder 2 and 3 .... To me it looks like the camshaft 'needs to be cut in the middle' and the having the one half turned 180 degrees and put back together ....
Just FYI, in most inline 4 cyl engines I have owned and worked on, many different makes and models, made in several countries, firing order is 1342 not 1324. There may be engines that use 1324 but I have not come across one as yet.
A Flat Four is not the same as a Straight Four ...!I agree on the firing order on a straight four - but the original question was for a flat four ....This time I actually searched the page and found this :https://www.cad-modelltechnik-jung.de/construction-plans-model-engines.htmlOne of the last drawings show the powertrain on this unik engine -> throwing ALL my assumptions down the drain Not only are the inlet and exhaust positions not where I thought on the rear two cylinders - but the crank throws are with a single 'pin / big end' -> making the pistons go the same way - instead of opposite directions ....I have never seen a full size engine with this layout - but it simplifies the build + make it more compact.I conclude that the camshaft is shown (in the drawing) with the pistons at either TDC or BDC. I will look at the last post before this to (hopefully) verify.
Coincidentally I just got delivery of the same plans. I'll wait to hear of any communication response you can pass along.When I've emailed him a few times in the past, seems like eventually he does get to them. Is it more the cam phasing you are wondering about or the individual timing parameters? I built myself a spreadsheet so I could digest this information (pertains to a glow radial) but eventually I could/will evaluate for this engine. I suspect, but don't know for sure, he sticks to similar recipe among his various engines.
I'll be watching along glorfindel. I'm just starting the same cad exercise myself.... and not trying to get too distracted from my radial build.- what is your rationale for changing the bore slightly from nominal metric to nominal imperial units by the little amount? Aren't the rings going to be sized based on resultant bore whatever it is (Trimble method), or do you have some other method in mind?- what features of the Edwards pushrod system are different or better than this design in your opinion?- not sure if you saw my inquiry post here on the forum about the Hirth coupling, but just wondering if you plan to adopt that feature on the crankshaft or have something else in mind.
Quote from: petertha on January 17, 2021, 05:35:32 PMI'll be watching along glorfindel. I'm just starting the same cad exercise myself.... and not trying to get too distracted from my radial build.- what is your rationale for changing the bore slightly from nominal metric to nominal imperial units by the little amount? Aren't the rings going to be sized based on resultant bore whatever it is (Trimble method), or do you have some other method in mind?- what features of the Edwards pushrod system are different or better than this design in your opinion?- not sure if you saw my inquiry post here on the forum about the Hirth coupling, but just wondering if you plan to adopt that feature on the crankshaft or have something else in mind.I already have a 1-3/8 reamer ;-). I dont like how he make the rings. He seems to make an over sized ring... I will use my own piston design, with 2 0.050" square rings, and my own conrod design with bronzeBushing instead of a needle bearing.I'm not fixed on the pushrod system yet...I will work on it today and post some updates.Envoyé de mon SM-N975W en utilisant Tapatalk
I can't see any need for the push-rods to be angled. As far as I can see, the cam box could be altered so that the cams could be spaced to allow the push-rods to be square. On the other hand angled rods are not uncommon and that slight angle is not likely to be a problem, except that it will eventually cause the tappet holes to wear oval.I don't like the skinny little tappets either. Are they supposed to have a slightly domed end, or are they flat?
I haven't modeled it as far as you but I tend to agree, why not align the pushrods straight & adjust the cam lobe spacing accordingly. There appears to be room to extend the cam box housing & end bearings fore & aft to accommodate. I was also wondering to myself if maybe the rockers might be sitting at in a bit different position along the axle, but the general assembly shows as you have it - right adjacent to the upright supports. Sometimes things become more apparent as you get deeper into the design. And sometimes they don't haha.
I still dont know what to do with the coupling.... I can use a graving tool to do the hirth coupling.Do you have some pics of the "Schiling" way to do it ???
