Reversing an engine

Dellortoman said:
Well, they were simple to do because I already had a CAD drawing of the chain primary drive. All I did was overlay the red outlines of the gear PCDs.

I did a bunch of CAD drawings of the primary drive several years ago when Red and I were talking about conversion to a Morse Hy-Vo type chain. I think Red got as far as actually buying the chain and (blank) sprockets, which weren't cheap. But Andychain's duplex Merc chain appeared at about that time, and it seems to be performing pretty well so the search for alternatives got shelved. I still think it would be interesting to give it a try though.

Here's a drawing of the Morse type primary drive if anyone is interested. It has the same chain pitch as the roller chain so has the same numbers of teeth on the sprockets. PCDs and centre distance all fit too.
Click to expand...

You'd have to calculate the gear sizes to give you the same speed rotation at crank end and clutch end (as when used with chain), but you'll be able to work that out pretty easy Cam. And it wouldn't matter if all four gears weren't inline, the two middle ones could be offset to each other, as long as the don'd extend past the top and bottom of the casing. Now get to work.  ;)

I used RONSON GEARS www.ronsongears.com.au


 
In fact, one of the offset gears needs to pretty close to the bottom of the casing, so that it can pick up some of the slippery stuff and share it around with the others.
 
It's difficult to calculate drive efficiencies. There are formulae available to do it that take into account coefficients of friction etc. but it's a bit of a guess knowing what coefficients to use. The only way to really know what power losses are going on is to measure it.

From practical experience we know that a roller chain drive has a power transfer efficiency of up to 98% under ideal conditions, whereas a pair of spur gears has a drive efficiency of up to 99%. So if you could build a primary drive with the crank gear engaging the clutch gear directly, that would be the best option (which is why a lot of motorcycle engines are now made that way).  But a gear drive with 2 idlers has 3 meshing pairs so even under ideal conditions the efficiency of the whole drive train would be (0.98)3, or around 94%.

However, the key to a chain drive being efficient is the "ideal conditions" part of the equation. It must be new, good quality chain and sprockets, well lubricated and tensioned properly. The efficiency falls off rapidly as the chain wears or stretches. Gear drives tend to stay "new" for longer than a chain. So after it's been in service for a little while, a twin idler primary gear train may outperform a chain primary drive.

If money was no object, you'd stick with the chain and replace it every race meeting to maintain the efficiency of the drive.

PS:
It's worth noting that a final drive chain operates in conditions far from ideal, so its efficiency is well below optimum, especially as it wears out. It's a good argument in favour of shaft drive on road bikes.


 
chrisk said:
You'd have to calculate the gear sizes to give you the same speed rotation at crank end and clutch end (as when used with chain), but you'll be able to work that out pretty easy Cam. And it wouldn't matter if all four gears weren't inline, the two middle ones could be offset to each other, as long as the don'd extend past the top and bottom of the casing. Now get to work.  ;)
Click to expand...

That's exactly what I did to come up with the drawings I posted yesterday.
 
Chains are good!
and yes, I come from da cane fields. I know nothing!  :D

Dellortoman said:
If money was no object, you'd stick with the chain and replace it every race meeting to maintain the efficiency of the drive.
Click to expand...
However, if we had the budget?
I suggest we consider moving the clutch closer to the crank, if possible, for a direct drive?
And would need a clutch redesign (or nick one from the wreckers?) as the support for the gears is critical, so the gears need to be inboard, of the basket, like the 500 twins?
500-clutch_basket.JPG

no?  (dunno)

 
chrisk said:
Something like this? http://www.ashonbikes.com/sites/default/files/images/BMW_F800_balance_2.jpg
Click to expand...
a left-side clutch?    (thumbup)
a right-side output?  (thumbup)
a 6-speed box?        (thumbup)

Give that man a beer  :D
 
and 87BHP at 8,000rpm plus 63 ft/lb torque at 6,000rpm,

that is why I want to install one of these BMW/Rotax units in a 668 chassis, it does fit and even the gearbox sprocket has the correct amount of teeth for blistering performance, The F800R figures are the ones I quote
compare this to the standard Lav motor (claimed !! ??) of 65BHP at 7,800 and max torque at only 600 revs slower (?????) of 44ft/lb at 7,200rppm.

ditch the reversed motor project Red and build as above, I am told that North of 100BHP is available if you look for it, and just think of the weight.!
CLEM
 
What I will be looking forward to is Smarty mastering the rear wheel steering  (bolt)

that said I'm off for a kip see ya in Morgan Park  8)
 
Reversing starter motor free clutch, if starter motor is used.

I have thought earlier that many four pole starter motors can be probably easily reversed
just by turning the center sleeve (the part that has four permanent magnets inside) by 90 degrees. It swaps
the north and south poles of the permanent magnet section. No need to switch the polarity and therefore no need to isolate.
Reversing at any method if brushes are not at centerline of the axle can create problems to the brushes.

Reversing engine rotation (with standard cams) swaps the firing order from 132 to 123. I don't know does it have
any effect that should be taken in account to crankshaft vibrations.

One possibility: Reverse rotating engine with chain primary (tensioner on the top of the primary cover) and reversing type gearbox.


If the only thing to be solved is the gear box durability (not like 6 speed gearbox, different handling with reverse rotating crankshaft),
it would be interesting to hear which parts actually fail from the gearboxes. I mean sounds possibly lubrication problem to me,
not actually knowing what is the situation there. And what else on gearbox section is to be solved with this reversing than that would
not be solved with that extra bearing on the sprocket cover you made earlier? To eliminate the bearing in where two shafts are on inside another?

Direct drive gearboxes are also used on some drag racing vehicles so it should not be weak in principle, of course the design itself is a different thing.
Many of those V8 gearboxes have parts of similar size than Breganzie twin/triple gearboxes have.

Needle bearing solution should have multiple times load carrying capacity than bronze bush solution of similar size (when there
is enough oil film strength; needle bearing solution also needs more of this because of smaller contact area).
Here in Finland many lubrication problems from vehicles followed by very high surface pressures (leads to metal to metal contact)
and/or too less feed of oil (by design flaw for example) were many times easily solved with suitable extremely high film strength oils,
and sometimes increasing the oil feeding to bearings/sliding surfaces.





 
CLEMTOG said:
and 87BHP at 8,000rpm plus 63 ft/lb torque at 6,000rpm,

that is why I want to install one of these BMW/Rotax units in a 668 chassis, it does fit and even the gearbox sprocket has the correct amount of teeth for blistering performance, The F800R figures are the ones I quote
compare this to the standard Lav motor (claimed !! ??) of 65BHP at 7,800 and max torque at only 600 revs slower (?????) of 44ft/lb at 7,200rppm.

ditch the reversed motor project Red and build as above, I am told that North of 100BHP is available if you look for it, and just think of the weight.!
CLEM
Click to expand...

I wasn?t aware they were a Rotax engine ...... cor, maybe I just found the perfect motor for my spine frame?
 
was just reading a road test on the new Speedmaster from Triumph and it is right hand chain drive 6 speed box

 
MotoJouni said:
Reversing starter motor free clutch, if starter motor is used.

I have thought earlier that many four pole starter motors can be probably easily reversed
just by turning the center sleeve (the part that has four permanent magnets inside) by 90 degrees. It swaps
the north and south poles of the permanent magnet section. No need to switch the polarity and therefore no need to isolate.
Reversing at any method if brushes are not at centerline of the axle can create problems to the brushes.

Reversing engine rotation (with standard cams) swaps the firing order from 132 to 123. I don't know does it have
any effect that should be taken in account to crankshaft vibrations.

One possibility: Reverse rotating engine with chain primary (tensioner on the top of the primary cover) and reversing type gearbox.


If the only thing to be solved is the gear box durability (not like 6 speed gearbox, different handling with reverse rotating crankshaft),
it would be interesting to hear which parts actually fail from the gearboxes. I mean sounds possibly lubrication problem to me,
not actually knowing what is the situation there. And what else on gearbox section is to be solved with this reversing than that would
not be solved with that extra bearing on the sprocket cover you made earlier? To eliminate the bearing in where two shafts are on inside another?

Direct drive gearboxes are also used on some drag racing vehicles so it should not be weak in principle, of course the design itself is a different thing.
Many of those V8 gearboxes have parts of similar size than Breganzie twin/triple gearboxes have.

Needle bearing solution should have multiple times load carrying capacity than bronze bush solution of similar size (when there
is enough oil film strength; needle bearing solution also needs more of this because of smaller contact area).
Here in Finland many lubrication problems from vehicles followed by very high surface pressures (leads to metal to metal contact)
and/or too less feed of oil (by design flaw for example) were many times easily solved with suitable extremely high film strength oils,
and sometimes increasing the oil feeding to bearings/sliding surfaces.
Click to expand...

we don't use a starter motor on the race engines so no issue there.
in fact we had to reverse the direction of rotation on the Pingel remote starter we purchased to suit the right hand engine side connection so would suit us to go back to a normal Pingel starter

main aim is to get rid of the sleeve gear on 5th and gain an extra gear
current failure is always breaking the mainshaft where it enters into the sleeve gear due to bending moments caused by running 17" slicks thus increased load and too much power
we will know if our outboard bearing set up works by Sunday night as racing this weekend

we machine our race cranks and the final design is symmetrical so crankshaft balance and vibration should remain the same
I think

you are right in saying lubrication to the gearbox is an issue and is something we are looking at next time engines are open, been a bit rushed this time just getting this latest modification completed in time to make it to this race meeting

thanks all for some neat ideas, lots to talk about this weekend



 
redax5 said:
was just reading a road test on the new Speedmaster from Triumph and it is right hand chain drive 6 speed box
Click to expand...

Mind you, it's only pumping 76Hp through those gears.
 
Davo said:
Bevel drive connecting the crank and clutch, ooooh errrrr.  >:D  :LOL:
Click to expand...

You beat me to it Davo. I came up with the same idea last night. It's not as silly as it sounds. Put bevel gears on crank and clutch, then mount a short idler shaft with a bevel pinion each end to transfer the drive between them. A bit like two diff crown wheels with a short shaft between them.

The advantage of such a design is that the idler shaft and its bearings would be housed in a re-designed primary case, so there would be no need to modify the crankcases to carry idler bearings. In addition, it reverses direction with a single idler shaft, so only 2 pairs of meshing gears. Further, spiral bevel gears have slightly higher efficiency than spur gears, so the whole drive may end up having similar efficiency to a nice new chain drive, but chain stretch is eliminated so it will hold its efficiency longer than a chain.

It'll mean an odd shaped primary cover with bulges where the gears and bearings are, but it's not in an area that will get in the way of anything.
 
redax5 said:
was just reading a road test on the new Speedmaster from Triumph and it is right hand chain drive 6 speed box
Click to expand...
You beat me to it, Red. Was getting tyres swapped at a custom moto place in m suburb and they had a project bike based on a Triumph twin of some sort - and yep, noticed it had RH chain. Thruxton 900s were 5 speed, 1200s are 6.

I noticed because I'm using a Triumph 900 twin (TT legend?) rear hub and had observed that the cush drive rubbers were not symmetrical, seeming to have more cushioning rubber on the drive side if it was a LH chain. And indeed they are LH chain, so no idea why they went to RH on the later models. Obviously a completely new motor design.
 
Dellortoman said:
You beat me to it Davo. I came up with the same idea last night. It's not as silly as it sounds. Put bevel gears on crank and clutch, then mount a short idler shaft with a bevel pinion each end to transfer the drive between them. A bit like two diff crown wheels with a short shaft between them.

The advantage of such a design is that the idler shaft and its bearings would be housed in a re-designed primary case, so there would be no need to modify the crankcases to carry idler bearings. In addition, it reverses direction with a single idler shaft, so only 2 pairs of meshing gears. Further, spiral bevel gears have slightly higher efficiency than spur gears, so the whole drive may end up having similar efficiency to a nice new chain drive, but chain stretch is eliminated so it will hold its efficiency longer than a chain.

It'll mean an odd shaped primary cover with bulges where the gears and bearings are, but it's not in an area that will get in the way of anything.
Click to expand...

Thanks.

I thought it was quite a clever solution myself.  :D
 
Why not adapt the Laverda top end to a SpeedTriple bottom end, or maybe the old Yamaha XS 750? Might be less work than making cases/primary drive etc.
 
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