A 5cc Twin Shaft diesel engine

Tug

On your engine drawing you have a bolt hole in the crankshaft for holding on the hubs. It's common practice to use a male thread. The wheels need our be done up tightly they have a nasty habit of coming loose.

Picture of the Oliver copy wheel hub.

Oliver

On the subject of engine cooling, this is a modern 1.5cc tether car engine it has no cooling fins and the car has no flow of cooling air into it other than what the engine needs to breath.

Edited By Old School on 02/01/2020 13:23:38

I've just found something out - twice - do not write the post then open a posted image to check something as you lose the lot!!!

Ok thanks for the pics Oliver - very helpful. I had'nt given the heat sink potential any consideration but can see that that would assist. Looking at the last image it appears that there is some kind of compound set around the cylinder - I can only assume this is to do the opposite and retain a degree of uniformity of temperature. It certainly looks a powerful beast even if it is only 1.5cc. I guess this the kind of engine used in the streamliner type car.

The shafts were drawn as such to reduce the overhang (and to a minor extent the material used) - do you see a problem with using a hex head bolt/screw as opposed to a nut? What about L/H threads - do they get used to aid wheel retention? They can soon be changed to shafts though.

I notice the clean steel plate within the tyre, unlike the rubber covered area on the sellers site. I assume you have cleaned that off. How central do you find the hole to the tyre rim - I could envisage balance problems here maybe?

Liner and piston drawings done this morning - not too far to go now

Regards - Tug

Edited By Ramon Wilson on 02/01/2020 14:11:03

Oliver - I'm on the last throes of the drawings and have been doing the crankcase .

As the cases have been pre machined (but not finished) I have to machine the standard mounting lugs off and intend to attach a base. I note the engines some times sit at an angle so I have set it at a 15 degrees on it's base - is that in the right order? I assume that's to help cooling around the fins?

Thought's appreciated

Cheers - Tug

Tug

The reason for the sloping bases of some twinshaft engines is the back of the cars they were fitted in the base of the car sloped up so when the engine was installed it was level in the car. Have a look in Oliver story book.

All the engines I have used have had a "U" shaped bracket to hold the engines in and retain the engines lugs see the cobra car picture.

Perhaps it might be worth thinking about the csr it's going into before you remove the lugs.

Oliver

Thanks Oliver, had another check of John's book last night.

I haven't given too much thought to the car as yet only that it would be a single seat racing car of 30s/40s vintage.

I was thinking of a substantial ali plate chassis supporting a GRP shell but that's a long way off as yet. As you say though it must play a part in answering this latest query. I will do away with the angle but as this is going to be a dedicated application I'll still machine the lugs off and fit a base but keep it flat - much easier.

Parts drawings should be finished later today

Tug

Hi Chaps, a great start.....what happened next.!?

Purely as an aside, re the comment about wheels coming loose.

The GN cyclecars of the 1920s had the same problem, because they used RH threads for all wheels instead of LH threads on one side. In that way, all wheels tended to tighten with use rather than slacken.

Showing my ignorance of such things, is the purpose of a twin shaft engine so that one disc controls Inlet period, and the other the Exhaust period, together with the Transfer porting, to optimise events?

Howard

The reason for a twin shaft is to give direct drive to both rear wheels to avoid losses from a bevel gear if the engine were mounted along the length of the car or the need for belt/chain/gears to drive the axle if transversely mounted.

I understand Ramon has been working on other projects but is back on engineering at the moment though not this engine.

Hi John, (and Jason)

Despite best intentions I'm afraid this project has been put on the back burner for a while. The main reason is that once built it would be sometime before I could try it out due to the current circumstances so energy (not so much of that these days!) has been diverted elsewhere. It's not forgotten however, the drawings are all finished and the material bought, but when does remain an open question.

Thanks for your interest though - one thing's for sure if I do get back to it again I will post here about it

Regards - Tug

Thanks Tug,

regarding the drawings, I was wondering how a twin shaft engine is assembled? Could it simply have a long shaft sticking out of the rear of a 'standard' crankshaft, your drawing seems to have a second shaft with web that is coupled to the conrod/crank pin somehow?

Oliver, do you have any photos of your Chinese copy engine dismantled ?!

thanks

john

Edited By john Wells 3 on 07/09/2020 16:17:50

True, don't wander about with the editor open. Changing page is likely to zap content.

However! Provided your browser supports tabs (most do), you should be able to open a second logged in connection to the forum. The second tab is useful for reviewing other posts and threads and for uploading pictures. Close the second tab when finished, cos it's possible for the operator to get confused about which window is actively editing. Don't ask how I know...

Dave

John Wells 3 sent you a pm

Hello John,

I guess the GA drawing posted above is a bit misleading but it was done for my own use - I know what it means - but it could be a bit more informative I agree. The drawing of the crank should help

The housings each side of the crankcase are separate from the case and the crankshaft consists of two parts. As you look at the drawing the part on the left with the inlet is one part which is driven by an extension of the crankpin which is an integral part of the right hand crank. That locates in a slot/hole in the left hand c'shaft web. Assembly is bolting the drive side on first and bringing the opposite (inlet) side to meet ensuring of course that the drive pin locates in it's slot/hole.

Dave - Yes lesson learnt ! The second tab is the way round it but it's remembering to do it!! Twice bit once shy should be foremost of course but age tells it's toll at times - thanks for the reminder though

Regards - Tug

Edited By Ramon Wilson on 08/09/2020 09:31:35

Thanks Tug,

with my (very) limited knowledge of crankshafts etc, I thought the mass was used to balance the piston/rod assembly.

Does this need to be taken into consideration with the two seperate webs? i.e. do the two weights combined, balance the assembly?

Is there any reason why the second shaft could not run straight out of the rear of an existing crankshaft, for example converting an existing (aero) engine with a new shaft?

Apologies if this is just 'daft'

regards

john

Actually John as I looked at the crankshaft drawing on here this morning that very thought occured to me. I realised I have drawn both webs cut away in the usual attempt to aid balance but looking at the drawing this morning considered that this is probably not neccessary beneficial on the 'driven' side. I don't have the academic background to design such - more based on use of engines over the years.

By making the web circular on the driven side would not only remove any effect that a cutaway web might have on the balance of the basic engine but it would be much stronger in the area where the drive slot/hole is machined

Perhaps Oliver can comment on the 'web' format in his engines?

BTW Nothing is ever 'daft' if you don't know the answer so ask away.

Regards - Tug

Ramon, I thought you had modified the intake crank web as on the original drawings it is shown thicker on the counterbalance side but yours has it all one thickness so the other counterbalance on the drive crankshaft web would probably total to the same amount.

Hello Jason,

Yes I did modify it to suit myself as this is just using the case I made for a 5cc Nalon. When I drew it it seemed logical to make both webs the same shape but as said having a 'second' look at it yesterday I consider it would be better to have it as circular for the reasons said - plus of course it will reduce crankcase volume a little.

It would be interesting to hear what Olivers commercial engines are like in this respect so perhaps he will see this and let us know.

Regards - Ramon

Hello Tony - just noticed that this thread has popped up again. Never fails to amaze me how many different posts are made on here over such a short space of time to place another fresh post well down the list.

I can't answer your question directly but I believe there is a current problem in obtaining suitable wheels/tires.

Possibly Oliver - 'Old School' - could comment on this situation

With regards to the intention of building an engine I'm afraid to say I have not done anything further. This was due to some health issues beginning to surface after my last post which I'm now more or less on top of but mainly because of the restrictions of Covid. There seems little point in pursuing something if I can't get to use it as intended - certainly in the short term. The idea isn't dead - just on hold until we see how things develop.

I have been busy in the workshop though, finishing off a project that had sat unattended to for a while.

Regards - Ramon (Tug)