Good points to jack

[Smithfire67]

Morning chaps

Where are the recognised safe points to jack on the frame of a 3a? (Front)

I've been using the point about a foot backwards from the narrowing? Avoiding any welded seams. 

Also use a small hardwood chopping board I found for cheap in B&M with foam hot glued on one side, to prevent denting the frame.

Clive

[Smithfire67]

.....just wondered if there was a point midway between the wheels that it would put undue stress on the chassis etc

[BlueTR3A-5EKT]

8 minutes ago, Smithfire67 said:

.....just wondered if there was a point midway between the wheels that it would put undue stress on the chassis etc

The original jack points under the floor either side.  Factory thought that was the best option.  Chassis is reinforced to support the   original jack at those points.  
 

Just peel back the floor mats and take out the jack hole plugs.  

Edited September 24, 2023 by BlueTR3A-5EKT

[Hamish]

I have fitted a moss rad protection plate on my 3a primarily to attach my anti roll bar. I can jack my car on the rear fixings of this plate where the main crossmember is to just lift the front. It’s strong enough IF your jack is long enough. Red arrowed pic.

do NOT mistake the thin rad shield for the chassis member our you’ll crush the rad.

i tend to change my wheels a lot and tend to do it in pairs front and rear

Edited September 24, 2023 by Hamish
Borrowing Deggers picture from below

[Deggers]

4 hours ago, Smithfire67 said:

..... just wondered if there was a point midway between the wheels that it would put undue stress on the chassis etc

As Peter says, the factory jack points (and chassis brackets for an original jack) can be found through access holes in the floor.

With jack engaged, either side of the car could then be raised from within the cockpit.

Although, you'd still have to get out into the rain to change the tyre.  

Deggers

[ianc]

Lifting one side of the car using the factory screw jack is not easy for two reasons: the jack has a short arm, and one has to lean into the cabin to operate it.

I did it once some 60+ years ago on my TR2, then bought a very squat hydraulic jack!

I carry a screw jack in my TR4 and would never attempt to lift just one side of the car, just near a corner where I need to get a wheel off the ground.  With solid rear axle, one can lift on the spring near to its forward end.

I am fortunate that my TR4 has an exceedingly strong skid plate welded to the front of the chassis.  Because it has braces on the top, I am able to lift the front of the car on a trolley jack, then use axle stands or ramps to make it safe.

Ian Cornish

[Ian Vincent]

I have a U shaped bracket welded to the top of my scissor jack and lined with a hard rubber pad.  The bracket is shaped to just fit around the chassis members.  I jack either at the front where the chassis starts to narrow in or at the back just before rear spring hangers.  I've never had any issues with the car appearing strained by this.

Rgds Ian

[Smithfire67]

1 hour ago, Ian Vincent said:

I have a U shaped bracket welded to the top of my scissor jack and lined with a hard rubber pad.  The bracket is shaped to just fit around the chassis members.  I jack either at the front where the chassis starts to narrow in or at the back just before rear spring hangers.  I've never had any issues with the car appearing strained by this.

Rgds Ian

Interested to know whether you jack were the chassis is parallel with the car or past the seam were it starts to angle in....I'm a bit scared of the latter because I guessing the chassis is just welded together without a piece of square section tube indside the the frame to strengthen the join.

Clive

[jerrytr5]

You can jack on any part of the main chassis (but not the rad shield as Hamish says). You can also jack under the diff.

If any of those give you problems, you have a bigger issue.

Jerry

Edited September 26, 2023 by jerrytr5
Update - see later comments

[Lebro]

I don't jack under the difference as it puts a lot of strain on the joints where the tubes fit into the diff casting.

Bob

[Smithfire67]

Thanks for the answers everyone. 

Clive

[John Morrison]

12 hours ago, jerrytr5 said:

You can jack on any part of the main chassis (but not the rad shield as Hamish says). You can also jack under the diff.

If any of those give you problems, you have a bigger issue.

Jerry

Don't jack under the diff.

It cracks the joints where the axle tubes enter the diff housing and you 

get oil leaks, 

Ask me how I know!

John.

[Bfg]

Hi Clive,

From a former design engineer's point of view ; the strongest parts of a chassis are around the suspension mounts.

You ask specifically about jacking up the front, so I'd suggest ; the cross-member between the suspension towers is very robust, as are the parallel longitudinal chassis rails immediately adjacent to that cross-member.  It's noteworthy that these are under the front of the engine, and so lifting here specifically raises the concentrated mass of engine, much of its cooling system and ancillaries (like the heavy dynamo). In turn this minimises bending the chassis in a hogging fashion. 

For purpose of just lifting one front wheel then I'd most likely jack up under the wishbone and coil-spring mount. This compresses the road spring and soon lifts the wheel, whereas lifting under the chassis allows the suspension wishbones to drop, and then everything has to be raised even higher in the air.   Personally I much prefer to use a longer block of 2x4" softwood  between the jack and the chassis or suspension parts, which helps distributes the load more. Suspension bolts and hard edges tend to push into a softwood block, which in turn pins it (the block) more securely in place. Admittedly those softwood blocks do get chewed up after years of use, but as far as I'm concerned they're sacrificial.  

IMO the original jacking points of the early TRs were little better than a marketing feature, ticking the box for magazine reviews. It was a carry-over from saloon cars. Those under an open-top TRs lift too much of the car in the wrong place (hogging the chassis).  In practice they never worked very conveniently either. When I had a TR3 I used it just once, kneeling beside the open door and reaching in. The occupant of that seat & footwell had to get their legs out of the way (which unless you're really familiar with that person meant their getting out of the car), and then if I recall the seat squab &/or A-post was in the way of getting a good turn on the handle. Thereafter I reverted to a scissor jack (with softwood block) under the suspension.   

At the rear I would be jacking up under the leaf-spring axle clamps (using a softwood block once again). Alternatively I would jack under the chassis-rail immediately adjacent to the forward leaf-spring mount or under the damper mount. The idea of lifting in the middle of a tubular axle assembly ..to raise the weight of the back of a car, complete with spare wheel, and perhaps laden for touring and the best part of a half-a-full tank of fuel, seemed wrong to me.  When I tried it ; I found reaching underneath a low car to reach the jack was very long and so flat on your face awkward, and when the back of the car was raised it only sort-of balanced. As it rocked - the jack under the diff skewed. Being at the side of the road I had no axle stands with me. Had I been lifting a wheel off at that moment - it would have been very dangerous. No, for me it's very much more reassuring to lift one rear corner of a car at a time, and to block it up under a main chassis rail.  And then, if required, to move around to the other side to jack that up. I now do it this way even when working on the car in the garage with a long-reach trolley jack.  On the IRS TR4A I jack-up just forward of the spring-saddle of the trailing arm, which tends to lift the wheel and the chassis togther. 

BTW, I also like to block the diagonally-opposite wheel to prevent the car from inadvertently rolling forward or back.  I have a pair of triangular shaped wheel chocks for this - made from timber with a sanding belt wrapped around each (stapled in place) to stop them slipping.

Hope that is helpful, Pete

 

Edited October 9, 2023 by Bfg

[Smithfire67]

1 hour ago, Bfg said:

Hi Clive,

From a former design engineer's point of view ; the strongest parts of a chassis are around the suspension mounts.

You ask specifically about jacking up the front, so I'd suggest ; the cross-member between the suspension towers is very robust, as are the parallel longitudinal chassis rails immediately adjacent to that cross-member.  It's noteworthy that these are under the front of the engine, and so lifting here specifically raises the concentrated mass of engine, much of its cooling system and ancillaries (like the heavy dynamo). In turn this minimises bending the chassis in a hogging fashion. 

For purpose of just lifting one front wheel then I'd most likely jack up under the wishbone and coil-spring mount. This compressed the road spring and soon lifts the wheel, whereas lifting under the chassis allows the suspension to drop, and then everything has to be raised higher in the air.   Personally I much prefer to use a longer block of 2x4" softwood  between the jack and the chassis or suspension parts, which helps distributes the load more. Suspension bolts and hard edges do tend to cut into the softwood block, which in turn pins it place more securely. Admittedly those softwood blocks do get chewed up after years of use, but as far as I'm concerned they're sacrificial.  

IMO the original jacking points of the early TRs were little better than a marketing feature, ticking the box for magazine reviews. It was a carry-over from better saloon cars. Those under an open-top TRs lift too much of the car in the wrong place (hogging the chassis).  In practice they never worked very conveniently either. When I had a TR3 I used it just once, kneeling beside the open door and reaching in. The occupant of that seat & footwell had to get out anyway, and then if I recall the seat squab &/or A-post was in the way of getting a good turn on the handle. Thereafter I reverted to a scissor jack with a long softwood block under the suspension mount.     

At the rear I would be jacking up under the leaf spring axle clamps (using a softwood block once again). Alternatively I would jack under the chassis-rail immediately adjacent to the forward leaf-spring mount or under the damper mount. The idea of lifting in the middle of an assembly tubular axle ..to raise the weight of the back of a car, complete with spare wheel and perhaps laden for touring and best part of a full tank of fuel, seemed wrong to me. When I tried it ; I found the reach was very long and so awkward, and when the back of the car was raised it only sort of balanced. As it rocked in a most unstable manner, the jack under the diff skewed. Being at the side of the road I had no axle stands with me. Had I been lifting a wheel off at that moment - it would have been very dangerous. No, for me it's very much more reassuring to lift one rear corner of a car at a time, and to block it up. And then, if required, to move around to the other side to jack that up. I now do it this way even when working on the car in the garage with a long reach trolley jack.

Hope that is helpful, Pete

Yes very helpful Pete, pretty much what I do too. 

[oxf2]

The "don't jack under the diff" advice -- is that true for a Girling axle, a Lockheed axle, or both?

[Lebro]

Any - & on any solid axle car.

Bob

[RobH]

As I posted on the other jacking thread - do you want to gamble that the axle was designed for this?