FWD Gearbox in the rear

MikeHiow

MikeHiow

MikeHiow

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This isn't something I've openly spoken about on here, but I've hit a wall on a project and was hoping to get some suggestions from other people.

A while back, I inherited a home-brew car project which had been started by a group of people at GKN Aerospace. This is the real deal, and has even been strengthened by engineers that normally work on stress testing and strengthening aeroplanes and their parts.

We've opted for an A-Series out of a mini, which is now in-situ in the rear, driveshafts and gearbox all mounted and bolted up, but here comes the issue of the gear linkages.

Obviously, set up as it is now, the gears will be in reverse - whilst usable, this isn't ideal, so I really need to come up with a plan to reverse this.

I was hoping someone on here had done, or knows someone who has undertaken a rear/dual engine project in the past, and subsequently would have had to overcome this problem.
 
I'm sure I can remember something in the kit car world that solved this problem that was related to the use of bike engines. I also seem to remember that Honda run their engines the "wrong" way round so a honda gearbox may be of some use.
 
Changing to another gearbox is not an option unfortunately, the rear track is set to accommodate the mini gearbox and shafts.
 
MikeHiow said:
A while back, I inherited a home-brew car project which had been started by a group of people at GKN Aerospace. This is the real deal, and has even been strengthened by engineers that normally work on stress testing and strengthening aeroplanes and their parts.
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Werent that clever then if they hadnt come up with a solution for that problem! ;)

Why the A series, seems a bit of a cack engine to go in a kit car to me?

Any photos of said vehicle? :)
 
Gribs said:
I'm sure I can remember something in the kit car world that solved this problem that was related to the use of bike engines. I also seem to remember that Honda run their engines the "wrong" way round so a honda gearbox may be of some use.
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The B18 etc still has the gearbox linkage pointing backwards, engine run t'other way but box is on opposite side.

Im sure you could do something with a neutral pivot point behind the box which then essentially reflects the direction forwards. Tricky one thats for sure, particularly the rotation of the linkage rod rather than the more simple forwards and backwards..
 
Berger said:
Werent that clever then if they hadnt come up with a solution for that problem! ;)

Why the A series, seems a bit of a cack engine to go in a kit car to me?

Any photos of said vehicle? :)
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That wasn't their task ;)

A-Series was chosen because of the desired track, and how cheaply you can get them to 100bhp+, which is plenty considering the car weighs less than 300kg ;)

I've never taken any photos to this date, its been on hold for a few years due to a lack of time and space to do it, however, I'm moving to a new place with a garage next month, hence my rekindled enthusiasm for it.
 
Dog leg under the box with pivot points. Turn the gate plate 180 degrees for reverse.
 
linkage.jpg
 
Do you have any drawings, or better photos?

I don't know if its been my long day or I'm "reading" the picture wrong, but I'm still failing to see its use for my application.
 
Maybe I've read your requirements wrong. You have a Mini engine in the rear, I'm assuming, to make things easy, the plugs are facing forward?

So your selector is now at the very rear of the car. The dog leg goes under the box, the t-piece frame goes either side of the box and the second shaft down is sliding on a fixed piece attached to the t-piece.


That make sense?
 
Nice picture Fett, shows the concept perfectly.

I assume the A series box selector is a stub with a hole for the 'bitch pin so that would work.
 
If this is the real deal, firstly why have they used an A series and not something a bit more modern which will already have 100hp? Secondly why not just narrow the drive shafts if the track was an issue, since you've got to fabricate a whole subframe anyway. Thirdly why is the gearchange operating in reverse? This suggests to me they turned the whole lot round to put the engine on the other side and it's going to drive the wrong way :confused:
 
Jonny69 said:
Thirdly why is the gearchange operating in reverse? This suggests to me they turned the whole lot round to put the engine on the other side and it's going to drive the wrong way :confused:
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:confused:

In the mini the gearchange comes out of the back of the gearbox, pointing directly toward the gear lever. When you take the engine out of a FWD car to fit to the rear of something you don't turn it around (unless you want to go backwards very quickly), so in this case you end up with the gearchange exiting the box from the rear of the car. Since a gear lever mounted 3 feet behind your car is of limited usefulness, a linkage to route the remote change back under the engine and into the cabin is quite desirable.

I don't know why they used an A series, but it has significant advantages in terms of packaging to the modern solution of a transaxle on the end of an engine, so maybe space was limited?
 
MikeHiow said:
Seeing it in place, it makes perfect sense now, thats Fett.
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No worries. You should try and find a couple of books by Allan Staniforth...High Speed, Low Cost and Race and Rally Car Source Book. Really impressive with sound fundamentals and recommended even if you aren't building a project car for anybody interested in fast road set ups. He designed and built the Terrapin, pretty much speaks for itself. I have the books so I can always scan relevant sections if you find they are referenced elsewhere or buy them yourself...definitely worth it.

I'd like to know what this weighs when you've finished because 300kg minus the driver would be impressive considering probably half of that will be the engine. Pics as you build would be nice.
 
i think 400kg seems more likely. The atom weighs 450kg in base spec, so not sure how you can make a 150kg weight saving on that unless your building a slightly oversized go kart !
 
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