Back to the extra block studs

[Charles P]

I did raise this on the old forum but have some further questions (and the post didn't make the cut for the archive). Thanks to those that contributed earlier. 

After my block destruction I'm aiming to put at the very least an extra block stud at the rear. The engine is a 1928 magneto crankcase. 
The idea is to tap a thread into the crankcase through to the rear cam bearing. The space to fit the stud between the rear of the block and the starter motor casting is really quite narrow. 
My question is whether it's better to use a long stud bracketed from the head (as Pigsty do in this illustration ) or use another route. 
  IMG_0644.JPG (Size: 107.37 KB / Downloads: 1,131)
The alternative route is to bolt a bracket to the bottom of the block and clamp that down to the crankcase. 

Part of me is attracted the "clamp" approach of the bracket technique but the long stud from the head has a simplicity about it and it avoids tapping into the block (I'm quite keen to avoid any risk of weakening the block).

Does anyone have firm opinions either way?

Also in a magneto engine replicating this approach at the front is very hard if you want to run a dynamo. Any creative approaches welcomed. 

Thanks

Charles

[Alan]

Well, I'd go for the longest stud possible. More stretch length is good.

[Charles P]

Well, I'd go for the longest stud possible. More stretch length is good.

What I was pondering is described in my very poor sketch below.

The idea is:
1/ Tap a 5/16 thread into the crankcase/rear cam bearing
2/ Insert and loctite a 5/16 normal length stud
3/ Turn up a 1.75" length of 5/8 AF hex bar threaded 5/16 female in both ends to be a joiner.
4/ Torque the hex "joiner" onto the stud
5/ Attach the bracket to the head and insert the long stud into the hex joiner 
6/ Torque the long stud down to 5ftlb less than the hex joiner

The raionale is to provide a neat, repeatable set up where the crankcase doesn't just have a stud tapped into it with no clamping helping to support the metal around the stud.

   


Criticism and suggestions welcomed about everything except my draughtmanship!

Charles

[Alan]

If you look carefully, I think that's exactly what is done in the photograph. I'm wondering about waisting the long stud to increase the stretch length, too.

[Charles P]

If you look carefully, I think that's exactly what is done in the photograph. I'm wondering about waisting the long stud to increase the stretch length, too.

You mean use a properly made stud rather than a very long bolt!

I will acknowledge inspiration from the photo but I couldn't see how the torque could be set on the lower fitting. 

Next consideration, the front of the block.

Charles

[Alan]

Yes, always better to use a stud than a bolt, if you can.

[Geoff Harrison]

Charles - I've no experience with supercharged engines , however I have always 
converted both crankcase / block and block / head studs from BSF to equivalent UNF sizes.
5/16" BSF = 22 tpi , UNF = 24 tpi .
Seems to work on all my Ulster engines although my ex Reg Nice car has stated to leak oil
from the front of the block - I know this is BSF !
Just a thought .

[Austin Carr]

Yesterday, I went to the British Motor Museum and was interest to see one solution to keeping a head on a supercharged Seven's engine - 32 studs to hold the cylinder head down on the factory racing team's 70 bhp engine, giving 100 mph .

[dickie65]

Hi Charles,
If you have not sorted this out it would be worth considering making the rear block stud go down into the rear main bearing housing.
You would need to use a drill bush to guide the extended hole and use a long tap, or a extended one

[Zetomagneto]

Charles - I've no experience with supercharged engines , however I have always 
converted both crankcase / block and block / head studs from BSF to equivalent UNF sizes.
5/16" BSF = 22 tpi , UNF = 24 tpi .
Seems to work on all my Ulster engines although my ex Reg Nice car has stated to leak oil
from the front of the block - I know this is BSF !
Just a thought .

Geoff, why would you do that, a courser thread into aluminium gives a better fixing, your going finer, and damaging Crankcases at the same time.
I appreciate a finer thread will give a higher clamping force, but lack of clamping force is not the problem, the problem is stopping the studs pulling out of the Crankcase.
You refer to "all my Ulster engines" it would be a shame if you have damaged genuine Ulster Crankcases in this way.
If you have done this to all your engines, how do you know the tried and tested over 80 years BSF doesn't work? 
If you want higher clamping force, or less likely to come undone you could make some studs BSF at one end, cycle thread at other end, but unnecessary in my opinion.
Can you please enlighten me as I am always willing to listen to new ideas

Does anyone else have view on secure crankcase studs, I know of at least one successful racer who loctites his standard suds into the crankcase and immediately preloads them so that in the threads in tension are in metal to metal contact,i.e. The tension is not through the loctite film.

---

Well, I'd go for the longest stud possible. More stretch length is good.

What I was pondering is described in my very poor sketch below.

The idea is:
1/ Tap a 5/16 thread into the crankcase/rear cam bearing
2/ Insert and loctite a 5/16 normal length stud
3/ Turn up a 1.75" length of 5/8 AF hex bar threaded 5/16 female in both ends to be a joiner.
4/ Torque the hex "joiner" onto the stud
5/ Attach the bracket to the head and insert the long stud into the hex joiner 
6/ Torque the long stud down to 5ftlb less than the hex joiner

The raionale is to provide a neat, repeatable set up where the crankcase doesn't just have a stud tapped into it with no clamping helping to support the metal around the stud.




Criticism and suggestions welcomed about everything except my draughtmanship!

Charles

Charles, this looks like a good idea, tried and tested.Using this method helps to keep the top of the block intact with the bottom, whereas if you attach brackets to the base of the block there is still a possibility of the block breaking like your last one.