Nemett Jaguar--Canadian style

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Brian Rupnow

Design Engineer
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I have spent the last week looking at model engine plans. The Nemett Lynx is all the rage right now, and I will be following all of the builds that are currently happening. However, as nice as it is, I prefer to see a lot of the moving parts in action,i.e. pushrods, rocker arms, etcetera. The one thing I don't like about the six internal combustion engines I have built so far, is that they all have open crankcases, and they sling oil all over the place. I know that quite a few have built the two cylinder Nemett Bobcat. The Jaguar is basically the Bobcat with one cylinder lopped off. It has exposed pushrods and rocker arms, but the crankcase and timing gears themselves are totally enclosed. It appears to have "splash lubrication" for the rod and the main crankshaft bearings. I have a copy of Malcom Strides original metric drawings, and I an going through them and modelling them in 3D solidworks, from which I will create my own detail drawings in British Imperial "inch" dimensions. I have already found mistakes in the drawings, so it definitely pays to model everything first. After I get the modeling finished, then I will step away, have a good look at what I have done, and then make changes which make sense to me. There will definitely be changes, and yet, by and large it will still be Malcom Stride's engine---with a Canadian touch.---Brian
 
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Well there!!!---That's enough silliness for one day. I have modelled 13 parts and one assembly since 6:30 this morning. It's a nice day outside, time to get out my 1931 Ford roadster and go for a little tour.
 
Now I need help from anybody who has built this engine or the Bobcat. (They have the same cylinders and heads). The drawing of the cylinder head which I have has a fold right in the center of the drawing, and I can't make out the diameter of the large counterbore on the cylinder side of the head, and I can't tell the depth and diameter of the shallow counterbores for the valve guides.---I don't have a clear dimension of the cylinder i.d. either, only I assume it is 24mm, same as the o.d. of the cylinder liner.---Brian
 
Replied on the other side.

J
 
Well, I got my question answered and kept on modeling. This is a section view of the current state. I don't have any bearings in yet, and I'm not sure about the location of the flywheel, as I haven't modeled the tapered bushing that locates it yet. I am quite surprised at the number on mistakes I am finding as I work my way through this. I am certainly glad that I just didn't accept the drawings as being correct and start machining. I couldn't understand why the cylinder has a liner in it. Now I see---it shows up in the section view. At bottom dead center the piston skirt extends below the cylinder by quite a bit. There is an assortment of ways to get around this, but so far I am modeling exactly as per the drawings, (except for mistakes that I keep finding and correcting).
 
Brian-

Another example of perfection. Thanks for sharing your concepts, for proving the design, and for correcting the mistakes. Can't wait for the metal version.

Frank
 
Brian, I have listed quite a few errors in your rendering over on the other site. To be fair to Malcom I see more errors on your drawing so far than I do on his plans.
 
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The Nemett Epidemic or craze coming. Best to take cover.th_wav

The Nemett Virus must have mutated into Lynx,Bobcat,Jaguar etc etc. Will be fun watching following HMEM members building their version of Nemetts.th_wav
 
OK. Gus just got infected too. Will build a Jaguar too but will be 2015. Geared cam drive and push rods.

Brian, When can see your Canadian Nemett-Jaguar going.
 
Okay--a few admissions to make. I read through the 42 pages of build notes last night (which, by the way are excellently done) and realized that #1--I have the sump bolted on upside down. #2--their is a different bolt circle in the bottom of the cylinder as opposed to the bolt pattern in the top. #3--Something is said about the rocker arms being right and left hand which I had completely missed. Once I take all that into consideration, there are far fewer mistakes in the drawings than I originally alluded to. The drawings I have all appear to have been scanned by folding in the center to get them small enough to copy on a scanner, and every damn one of them has missing dimensions right at the "fold".--And its amazing how many parts were drawn right in the center of the drawing where the fold is. I hate it when there is no overall general arrangement to see how the myriad of pieces all fit together. With this engine they supply a lot of very good photographs with the build notes, and I guess you have to suss out how all the parts go together by finding them on the photographs.--I'm not accustomed to working like this. George you are right---the piston crown is far too thin as drawn, as are many other parts, (in my estimation). First thing I will do today is correct the model, second thing is to return a phone call to Toronto about some "real work" I was asked about bidding on.
 
Gradually I am getting this sussed out. The modeling is almost completed. I haven't done anything with the timing gears yet. You see one section taken thru the engine at the center of the cylinder, one section taken thru the center of the engine at the camshaft, and one blow up of the rocker arm area. Something is very fishy with the crankshaft. The bill of material calls for 3 main bearings (in red) all with a 10mm i.d., but the center bearing is setting on a portion of crankshaft that is called up as being 12 mm diameter. The crank is a tad short on one end too. I will read thru all of the design notes tonight and see if I can pick up any clues.---The original designer MAY have meant the center bearing to be 12mm i.d which would make the crank correct in that area, but the crank would still be a bit short on the left hand end. The section thru the camshaft looks okay at a quick glance, but I may be missing a spacer on the right hand end to help position the bearing.


 
OK. Gus just got infected too. Will build a Jaguar too but will be 2015. Geared cam drive and push rods.

Brian, When can see your Canadian Nemett-Jaguar going.

Gus--It's summer time!!! I am not in a rush to machine anything yet. I will first complete all of the modeling as per the original drawings, then decide what changes I wish to make, then model all of the changes. I am not going to make any forecasts about "when" I will have a running engine.---Brian
 
As I said read through the threads on ME forum, the bearing spec has been covered, you want a S61801 which is un shielded, 12mm bore,21OD, 5mm thick

Spring keeps are upside down, the spigot fits inside the spring, the e-clip in the recess
 
As I said read through the threads on ME forum, the bearing spec has been covered, you want a S61801 which is un shielded, 12mm bore,21OD, 5mm thick

Spring keeps are upside down, the spigot fits inside the spring, the e-clip in the recess
Thanks Jason----Brian
 
Didn't get much play time today.--Worked all day on that small contract I went to Toronto to see about yesterday. I did manage to get the correct mod 0.8 gears downloaded and installed. When I get to my build, I will be using 24DP gears because that's what cutters I have.
 
I am finished modeling the Jaguar. It seems to be a well thought out engine, and I am confident that it will work as designed. The drawings are somewhat difficult to read, due in part to the fact that when they were photocopied there are dimensions missing right at the crease in the centerline of the drawing, and there are a few minor errors. On top of that there is the fact that without a completed general arrangement it I found it very difficult to figure out where some of the parts actually went on the engine. As I understand things, Malcolm Stride created the first draft of these drawings and then unfortunately passed away. --It's pretty hard to go back and tidy up your original drawings once that happens!!! I haven't bothered with the exhaust pipe nor with the carburetor, as I will not be using the ones in the original drawings. There are a lot of things that I like about this engine. There are one or two things that I really don't care for, but they are cosmetic. I really don't like the square box shape of the crankcase--it looks like something you would find on a Russian tank!! The nicely rounded profile of the cam chain cover doesn't go with that box shaped crankcase. However, as I said, these features are cosmetic and will not detract from the running of the engine. now I will resave all of the files as a different part name and begin to make the changes I want.----Brian
 
The Jaguar is morphing into something else----

Nice work Brian. Look forward to the build.

- By 'something else' you mean you are converting from original glow to spark ignition, or...? (I don't know what the original Jaguar was designed around).

- if I understand, you converted original timing gears from metric to Imperial because you had cutters. So did that move the stock camshaft center relative to crank? Or maybe that remained & just the idler gear moved? I guess it doesn't matter if you are producing all new plans anyway, just wondering.
 

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