Single cylinder semi diesel
Adrian R2 | 01/02/2021 10:16:48 |
196 forum posts 5 photos | Good stuff. I don't think I'd fancy furnace work in 30C, well, not unless you have one of those closed and insulated electric ones. On the plus side less chilling from the moulds I guess. |
Four stroke Fred | 04/02/2021 08:11:24 |
![]() 322 forum posts 305 photos |
|
Four stroke Fred | 08/02/2021 07:36:33 |
![]() 322 forum posts 305 photos | Earlier on I said that I had found a worm gearing system that suited the the steering box well the truth is it was the correct size but unfortunately it was right handed and no good for the tractor - must have had a seniors moment, If I had used it the driver would have turned the steering wheel to the right but the tractor would have gone left ! After checking on the internet I discovered that most commercial worm wheel sets are right handed. The challenge was then to make my own that fitted the criteria and today I think I did just that. I still have to check and finish the matching pair but hopes are high. Yesterday I assembled the gearbox and joined it to the chassis, Gearbox is10kg and chassis 8kg. Fred.
|
Henry Brown | 08/02/2021 10:20:31 |
![]() 618 forum posts 122 photos | More great work Fred, really enjoying your adventures! |
Tim Stevens | 08/02/2021 18:38:32 |
![]() 1779 forum posts 1 photos | I have a message for Roger - I hope he is still reading this story I suspect that the Field Marshal is going to be a real problem to get running nicely. This is because its working depends on the shape and size of the exhaust system. As the exhaust port opens, the rush of gas is intended to overshoot, rather - drawing fresh air into the pipe as the 'bang' reaches the narrowing at the far end. This causes a reflection of a pulse back towards the engine, and this pushes the fresh air back into the cylinder, just in time to be trapped by the exhaust port closing, improving the compression and turbulence, for more power. This process needs to be 'timed' with the engine rpm, of course. But the timing of pressure reflection in the pipe depends on the length of the pipe. So a half-sized pipe on a half-sized model will need to rev at twice the RPM to work properly. So, your tick-over will not sound anything like the low beat of the original. If you can get it to work at all ... If I can help explain further, please send me a Private Message and I will do my best. Regards, Tim |
Dominic Bramley | 08/02/2021 19:33:24 |
60 forum posts 1 photos | Looks great Fred! I'm really enjoying following this build! Cheers Dom |
Roger B | 08/02/2021 19:45:01 |
![]() 244 forum posts 105 photos | Thank you Tim, I fully understand the problems of scaling real life and am learning the additional problems that come with two strokes. I will be happy if I can get a operating range between 2000 and 4000 rpm. A 500rpm idle is out of the question. It sort of runs but the injector atomisation requires some more work.
|
Four stroke Fred | 08/02/2021 20:31:53 |
![]() 322 forum posts 305 photos | Thanks for the comments and I am pleased that you enjoy reading about the construction of this model. For me it’s going into the unknown that is exciting as I enjoy the problem solving as well as the construction. The part I am working on is the model of the day and in the end they all add up to the completed model. I am looking forward to making the engine as I know there will be plenty of problem solving there. Fred. |
Four stroke Fred | 09/02/2021 07:59:02 |
![]() 322 forum posts 305 photos |
|
Four stroke Fred | 12/02/2021 07:46:16 |
![]() 322 forum posts 305 photos | As you can see the steering box is now finished and now has its position on the side of the gearbox. I had to make the steering wheel shaft and temporarily fit it to the box as it I had to set the shaft at 66 degrees to the horizontal top of the main gearbox. The steering arm that fits onto the worm wheel shaft has been shaped but has yet to have the square hole made at its pivot point. |
Four stroke Fred | 14/02/2021 09:33:33 |
![]() 322 forum posts 305 photos |
Fred. |
Four stroke Fred | 14/02/2021 09:35:07 |
![]() 322 forum posts 305 photos |
Fred. |
Four stroke Fred | 18/02/2021 08:03:19 |
![]() 322 forum posts 305 photos | This is this weeks”model”. It’s the gear change lever and as small as it is it’s fiddle and takes time. It’s a case of fingers too big and parts too Fred.
|
Four stroke Fred | 28/02/2021 07:07:38 |
![]() 322 forum posts 305 photos |
Fred. |
Howard Lewis | 28/02/2021 11:08:45 |
7227 forum posts 21 photos | FANTASTIC work! Howard |
Howard Lewis | 28/02/2021 14:01:06 |
7227 forum posts 21 photos | Without wanting to hi jack Fred's thread, have been thinking about Roger's model of a Marshall, and Tim's comments. Tim is right that the early two strokes relied upon a "Harmonic" exhaust system to scavenge the combustion products from the cylinder, and to partially charge it. Because this relied upon the exhaust system being in resonance, the engines were virtually constant speed units, to stay close to the resonant frequency. Anyone who has heard a Marshall two stroke running will testify to this A model of a Marshall, running at 2,000 rpm, will sound anything but prototypical! The dynamic magnifier curve is extremely "Peaky", so that a comparatively small deviation from the resonant condition can result in the loss of the advantage. What works well at 2,000 rpm may do nothing at 1950, or 2050 rpm. Witness the need for speedway and motorcycle racers to stay "on the meg". Similarly, at 1,000 or 4,00 rpm the system may do just the reverse of what is needed, as the engine and exhaust pulse are then completely out of phase. The resonance depends upon the speed of sound under the temperature conditions prevailing in the system, but that, unlike the components, cannot be scaled. So to have an engine that runs in any way like the prototype, there will be the need to depart from the original. It may be possible to lengthen the exhaust tract, and yet apparently stay with a prototypical looking "silencer". A 1/6 scale model would need the exhaust system to be six times as long, as scale, to reproduce the conditions of the original. It MAY be possible, but not easy, to fold the exhaust pipe into an extended coil. and site it within the "silencer" outline, so that actual length is possibly three or four times the apparent length, whilst keeping the divergent- convergent external form. Just a suggestion.. Howard.
|
Roger B | 28/02/2021 17:03:59 |
![]() 244 forum posts 105 photos | Splendid work on the Mc Donald Howard, all the work on the diesel engine as well as petrol and diesel fuel injection systems is on Model Engine Maker. So as not to take over this thread I am happy to continue discussions on there. https://www.modelenginemaker.com/index.php You need to be a member to see the pictures. I initially ran the engine as a petrol engine with a different cylinder head to prove the porting would work. In this form it would run reasonably slowly but I don't have enough space for a big enough flywheel to allow the diesel to run at low speeds, the compression pressure is around 30 bar.
|
Four stroke Fred | 28/02/2021 21:44:54 |
![]() 322 forum posts 305 photos | The exhaust system on the Mc Donald that my model is based on has a straight through pipe but I have seen a spark arrester fitted to another. The full sized engine ran at about 500rpm and I hope to keep the revs on the model low, helped by a heavy flywheel. I am looking forward to making and developing the engine and hearing the exhaust beat. My other interest is motorcycles and their development and I can remember being in the pits at Brands Hatch in the 1960s and seeing the East German MZ with Walter Kadem their design engineer. These machines used a resonant exhaust system to very good effect and was later taken up by the Japanese companies. On my model I will use the straight through pipe as am not after maximum power and will very very happy to just hear and see it move and also try to keep as it was on the original. Thanks for the comments. Fred. |
Four stroke Fred | 01/03/2021 07:54:03 |
![]() 322 forum posts 305 photos | Over the weekend I had a visitor to the workshop and on seeing the tractors, boats, I.C and steam engines on display asked ” “where do you get the instructions from to make these ?” I had to inform him that they were home designed and made and that I had spent 17 hours so far photographing and measuring up the Mc Donald tractor and as for instruction you make it up as you go along. As you work on one part you are thinking of the next part and how they will relate to each other. The rear wheel hubs have now been turned down to size and will soon be ready for silver soldering. I have now checked the angle that the spokes have to be bent to and will make a jig for this repetitive exercise. Photo shows milling the pockets in the rear hub - as it was not a full circle great care was needed! Fred. |
Four stroke Fred | 01/03/2021 07:57:59 |
![]() 322 forum posts 305 photos |
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
Sign up to our newsletter and get a free digital issue.
You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.