Benefits of a Midget crankshaft?

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bmcecosse
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Re: Benefits of a Midget crankshaft?

Post by bmcecosse »

That last pic shows how little overlap there is between the big-ends and the mains....
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philthehill
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

bmc
I agree there is very little crank journal overlap compared with the Marina/Ital crank journal overlap but the Midget/Sprite crank is made from much better material so does not require the larger overlap which was adopted along with the rolled fillet between the crank journal and web to overcome the deficiency in the material used for the Marina/Ital 1275cc crankshaft.
Crankshafts using the rolled fillet process at the start of production were faulty due to poor machining tolerances and which raised the possibility of total failure of the crank at the rolled fillet.[frame]Image[/frame]

bmcecosse
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Re: Benefits of a Midget crankshaft?

Post by bmcecosse »

My understanding is that the rolled fillet was introduced on Mini cranks because of previous failures on cranks which didn't have the nice 'rolled' fillet. I think that's what you are saying ....
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philthehill
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

bmc
Yes - in a roundabout way; the rolled fillet was introduced as you say but it did not work out well for BMC/BL.
It was introduces to remove any right angle/sharp angle between the crank journal and crank web which had resulted in cracking and failure in the angle between journal and web of pre rolled fillet crankshafts
Unfortunately when the rolled fillet was applied in production the application was not as it should have been which resulted in quite a few faulty crankshafts which either failed or had the possibility to fail in the angle between journal and web.[frame]Image[/frame]

millerman
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Re: Benefits of a Midget crankshaft?

Post by millerman »

Phil, thanks once again for photos and explanations.

After a quick measure the Minor g'box output shaft is 0.5" diameter and the Type 9 output shaft is 0.6" diameter. Google yielded this image:[frame]Image[/frame]

So I need to purchase this carrier and spigot bearing to suit the type 9 output shaft and will the crank need modifying to fit this carrier?
What are the advantages of roller bearings over the plain bearing in the diagram? I wont be racing but I do keep up with motorway traffic often towing maybe more the a Trav was designed to tow so I need reliability!
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Re: Benefits of a Midget crankshaft?

Post by bmcecosse »

As long as the clutch is driving - there is no relative movement between bush and shaft. I would just use a plain oilite bush. Would it not be easier to reduce the shaft to 0.5 " ??
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millerman
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Re: Benefits of a Midget crankshaft?

Post by millerman »

bmcecosse wrote:As long as the clutch is driving - there is no relative movement between bush and shaft. I would just use a plain oilite bush. Would it not be easier to reduce the shaft to 0.5 " ??
I have thought of that but no lathe and my engineering skills are not that good :(
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

Good work on finding the Google diagram.
The adapter with iolite bush would be satisfactory in normal use.
The Ford and Marina/Ital gearboxes both use a roller bearing in the rear of the crankshaft for the support of the first motion shaft so I considered it prudent to use the roller bearing arrangement.
I would not recommend using a lathe to reduce the diameter of the spigot shaft. If you do reduce the shaft diameter it should be precision ground as you get a much better finish which would not wear away the inside of the oilite bush.
Not only has the diameter of the spigot bush/roller bearing to be considered but also its lateral position in the rear of the crank. Note on my crankshaft the roller bearing and adapter sit proud of the end of the crankshaft. The Google sourced adapter also sits proud of the rear of the crank by 2.82mm.
Here is the link to the instructions for fitting the Ford gearbox which shows the use of the adapter:
http://www.moss-europe.co.uk/graphics/u ... lation.pdf
It may be worth a call to Front Line Developments tel: 01235832623 to ask if the adapter they provide in the kit is available separately and as to it suitability for use in a 1275cc Midget/Sprite crankshaft.

Update: 09:44
I have just finished speaking with Front Line Developments and the adapter is suitable for the midget crankshaft but may need some fitting (nothing serious and nothing that cannot be easily overcome and/or carried out). It also needs the Midget/Sprite 1275cc flywheel as the Midget/Sprite flywheel keeps the adapter in place.
The adapter/oilite bush is available at £19.51 plus the usual. No part number was to hand when I spoke with them but they readily knew what I was referring to.

Phil

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Re: Benefits of a Midget crankshaft?

Post by bmcecosse »

Top marks service there Phil! :D
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Re: Benefits of a Midget crankshaft?

Post by millerman »

Phil, thanks again. All I need do now is put everything into practice :D
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

Millerman
Just a thought!
Whilst you have cleaned the outside of the crank and it looks very good - have you run a brush through the oil ways?
There may be crap in there that could ruin a bearing/journal.
If you have not got any oil way brushes they are available from www,frost.co.uk item No: C170.
They can also be used for cleaning out the various oil ways in the block and head etc.
Phil

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Re: Benefits of a Midget crankshaft?

Post by millerman »

Thanks all for comments and advice

Spigot and carrier have been ordered, as soon as that is fixed to crank I shall start the engine build
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Re: Benefits of a Midget crankshaft?

Post by millerman »

Thread resurrection

Engine has been built :D ready to go in the Trav!

I am replacing the existing Marina engine which has a Type 9 gearbox with the Midget engine

Next question is: will the flywheel/clutch cover/plate fit directly on to the Midget crank without further work being done?
I have the Midget flywheel but no clutch so would rather use that which I have. My previous experience of a Midget diaphragm clutch in a Minor was not good!

I have carried out an internet search but really haven't come up with a definitive answer ie from an owner who has carried out the above modification

Cheers all
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

The Marina flywheel will not fit the 1275cc Midget crankshaft and is not suitable for the conversion you are undertaking (too big).
The Midget clutch cover is suitable for use with the Midget 1275cc engine/flywheel/Ford first motion shaft BUT NOT the centre plate.
You will have to change the clutch centre plate to a fine spline centre.
As regards the clutch release bearing there are several methods in use for depressing the clutch release bearing.
See Frontline Developments for details of one method and fitting instructions.
They are very helpful and they will not bite if you want any advice on fitting.

http://frontlinedevelopments.com/produc ... 75cc.shtml

You could always use the ESM modified flywheel (Pt No: 10M001) for 1300cc engines and a Ford 7.5" clutch assy.

Do not forget that what ever you use you will need the Ford first motion shaft bearing adapter (available from Frontline Developments) and which fits the end of the Midget crankshaft/flywheel. Details in their instructions.

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Re: Benefits of a Midget crankshaft?

Post by bmcecosse »

Were you really using a 'Marina' flywheel (which as Phil points out is larger diameter) - or a Minor flywheel that had been adapted to fit the Marina crank? If the later - surely it will fit the Midget crank.....
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

The ESM modified flywheel is capable of being fitted to both Marina and Midget.
The difference between the Marina and Midget crank is the difference in the size of the register and that the Midget has two locating dowels and the Marina only one.
I understand that the ESM modified flywheel has no register to fit over the end of the crankshaft as per the Midget and Marina but just fits flush against the end of the crankshaft which for normal use is quite satisfactory and the modified flywheel is capable of accepting both two and one locating dowels so quite a versatile flywheel.
The register on both the Midget and Marina were deliberately made different so that during factory assy the wrong flywheel could not be fitted to either the Marina or Midget engine.
This engine currently on 'e' bay has had the modified flywheel fitted and whilst the flywheel has the extra dowel hole it is not used as the crankshaft is still Marina :-

http://www.ebay.co.uk/itm/MORRIS-MINOR- ... 339ca9a27a

It is also suitable for the 7.5" clutch.

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Re: Benefits of a Midget crankshaft?

Post by millerman »

bmcecosse wrote:Were you really using a 'Marina' flywheel (which as Phil points out is larger diameter) - or a Minor flywheel that had been adapted to fit the Marina crank? If the later - surely it will fit the Midget crank.....
Thanks BM and Phil for replies.

I'll spend half a day and remove my Marina/type 9 gear box and see which flywheel I've got. If it's a Minor flywheel then, presumably, with drilling another dowel hole it will fit the Midget crank or can I remove one of the dowels in the Midget crank??
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Re: Benefits of a Midget crankshaft?

Post by philthehill »

A normal Minor flywheel has only 4 bolts and no dowels.
The Marina and Midget both have 6 bolts.
The Marina has one dowel and the Midget has two.
Examine your existing flywheel/clutch and see what you have got - look especially at the flywheel crankshaft register.
I suspect that you may well already have the modified flywheel and clutch centre plate if you already have a 1275cc/type 9 fitted.
A photo of what you have would be appreciated.
Best of luck.
Phil

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Re: Benefits of a Midget crankshaft?

Post by millerman »

As soon as I get everything apart I'll post a photo :D

Thanks all
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Re: Benefits of a Midget crankshaft?

Post by bmcecosse »

Use all the dowels you can..... :(
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