Rivnuts to mount battery

[StuartsProjects]

The frame triangle on my bike is quite small, see attached picture. The frame is titanium and some Googling suggests the tubes are 0.9mm thick.

Whilst I intially thought a bottle type battery (36V 10Ah) would fit, a diagram I saw (see picture) suggests there might not be room in the frame to lift the battery clear of its bracket.

I watched a video of someone fitting a Hailong type battery of the same size in a small frame and it looks like the battery is placed over the bracket and slid back around 3cm to lock in place, so there is not so much of a clearance requirement above the battery. I made a cardboard template of the battery and the battery base is some 25mm clear of the frame tube when the cardboard battery is placed above where the bracket would be.

However its likley the existing bottle cage nuts are on the wrong place, a common problem I guess, so I assume there is a need for rivnuts to be used. There is a close up picture of the top of the frame tube.

Is there likely to be room to get one of those right angle drill adapters in to drill the holes ?

What type of rivnut to use, alluminium, steel, stainless steel ?

Are there alternatives to rivnets ?

The fallback plan, if a battery cannot be placed in the frame, is to put it on a rear pannier.

The controller is currently planned to go in a bag behind the saddle, there is not really much room between the seat tube and wheel\mudguards.

 

[Zlatan]

I, ve used stainless rivnuts quite a lot, find these are much stronger than aluminium but harder to put in. Last bike I did I couldn't use rivnut tool(an oversized rivit gun, capable of fixing upto m12 rivnut) on upper battery to frame fixing (not enough room to get in) so used bolt, nut /washer/spacer to fix it in place. (much harder to use than rivnut tool)
I, d have thought 0.9 mm wall thickness is fine for upto m6 rivnuts, but I, d use m4 for battery fixings. ..., but it also depends on radius of tubing.. (thin tubing irrespective of wall thickness can be problematic for rivnuts)
As an aside I had to reinforce my boat trailer to accept more powerful winch. For a couple of reasons I had to use rivnuts, was worried they wouldn't be upto job (used m10 stainless x4) Boat weighs 1580kg and winch is still doing a great job 3 years later.
Put them in properly and ruvnuts are fine, make a mess of them... They will spin... (I always put them in with loctite permanent.) Rivnut will be stronger than tubing.. Not had any spin or pull out since using rivnut tool.
But, I always put a strap around battery /frame. Even on my Haibike.. Belts and braces... Keeps stress off rivnuts. Repairing a spinning one is worse than fitting one..

 

[StuartsProjects]

I have seen it recommended to fit rivnuts in plact with 'JB Weld', so I guess some standard epoxy resin would do much the same and prevent the nuts twisting.

I have seen the bolt method to fit the rivnuts, it was on the video I saw of the guy fitting a HL battery.

The downtube has a flattish area on top, where the bottle nuts are, I copies the profile with one of those shape copier things and have attached it as an image.

 

[vfr400]

Titatium is next to aluminium in the electr-chemical series ansd on the zinc and iron side, so there should be no problem to use ordinary zinc plated steell rivnuts. I would make that my plan A. Try to find rivnuts with the biggest flange on them, as they're the most secure to fit and take loads. I'd avoid stainless steel and aluminium ones because they both suffer from metal fatigue.

If you can't get in with a drill, like any that are close to the top or bottom corner of the triangle, you can use a Dremmel with carbide burrs. The hole doesn't have to be exactly round for the rivnut to work. In fact even a drill won't drill it round in a thin tube anyway.

Plan B would be to use some of these. you can loosen the clamp scres to rotate the battery round the frame if ever you want to get it off, though this is not the best solution if you want to take it off every day. There are lots of different versions of these adapters:

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I've never used any tools to fit rivnuts other than a 5mm screw and two flat strips of steel with 5.5mm holes in the end. JB weld and epoxy would be a complete waste of time. A rivnut is easily strong enough on its own if properly fitted. You can get away with two on a 2.5kg battery, but anything heavier than that needs three - always the more the better.

 

[Zlatan]

I have seen it recommended to fit rivnuts in plact with 'JB Weld', so I guess some standard epoxy resin would do much the same and prevent the nuts twisting.

I have seen the bolt method to fit the rivnuts, it was on the video I saw of the guy fitting a HL battery.

The downtube has a flattish area on top, where the bottle nuts are, I copies the profile with one of those shape copier things and have attached it as an image.

Yep, putting them in without proper tool is certainly possible but if at all possible use a tool.. Just slight turning of rivnut at wrong time will reduce strength a lot. (no spinning at all with tool)
Don't think the loctite or jb weld will increase strength much but will help prevent dissimilar metals corrosion.
I used to build Caterhams for a living and some of internal panels are better if you can remove them(gear box tunnel).. By experience we came to only ever use stainless rivnuts. Aluminium were a complete waste of time, older cars they would be white and rotting where in contact with steel and aluminium threads are aluminium threads.. Rubbish. We never saw any either rotted or broken stainless but the pressure they require to fix in can be a pain. Hence the tool.
Don't know tensile strength of smaller ones but a single m10 is over a ton, well over.
I, ve stopped using aluminium ones... Cheap and nasty. You get what you pay for.
But, I, ve never used titanium ones. Size for size good stainless is stronger than titanium.
Titanium is stronger per unit weight.. Titanium rivnuts will be lighter... But weaker.

You really are better with one of these, especially so with stainless..
Not only are they easier and rivnut is not going to spin you can feel when rivnut has fully collapsed. Putting in with bolts you can either over do them (damage thread) or under do them. (rivnut spins)...

 

[StuartsProjects]

I was thinking that two rivenuts might not be enough. And if you had only 2 and one failed, the weight of the battery might well bend up the tube around the remaining one.

I have a small 12V drill and a set of small dremel style grinders and cutters etc.

A small cone cutter on a tap\die handle might work too.

 

[vfr400]

Yep, putting them in without proper tool is certainly possible but if at all possible use a tool.. Just slight turning of rivnut at wrong time will reduce strength a lot. (no spinning at all with tool)
Don't think the loctite or jb weld will increase strength much but will help prevent dissimilar metals corrosion.
I used to build Caterhams for a living and some of internal panels are better if you can remove them(gear box tunnel).. By experience we came to only ever use stainless rivnuts. Aluminium were a complete waste of time, older cars they would be white and rotting where in contact with steel and aluminium threads are aluminium threads.. Rubbish. We never saw any either rotted or broken stainless but the pressure they require to fix in can be a pain. Hence the tool.
Don't know tensile strength of smaller ones but a single m10 is over a ton, well over.
I, ve stopped using aluminium ones... Cheap and nasty. You get what you pay for.
But, I, ve never used titanium ones. Size for size good stainless is stronger than titanium.
Titanium is stronger per unit weight.. Titanium rivnuts will be lighter... But weaker.
View attachment 42645
You really are better with one of these, especially so with stainless..
Not only are they easier and rivnut is not going to spin you can feel when rivnut has fully collapsed. Putting in with bolts you can either over do them (damage thread) or under do them. (rivnut spins)...

How are you going to get that massive tool in the corner of the triangle if you can't get a drill in to drill the hole?

 

[simon77]

are the super shark em3ev batteries from eclipse any good? Bit of flexibility on mount positioning. Nice battery too.

 

[StuartsProjects]

How are you going to get that massive tool in the corner of the triangle if you can't get a drill in to drill the hole?

If that question was directed at me, then a small tap\die handle and cone cutter is quite low profile, and on my frame will fit up to about 2cm short of the end of where the battery would be.

Not tried it yet mind.

 

[vfr400]

I was referring to the big rivnut tool in post #5. Eclipse batteries are good if they fit.

 

[StuartsProjects]

are the super shark em3ev batteries from eclipse any good? Bit of flexibility on mount positioning. Nice battery too.

Now that I like. Looks like no extra mount holes required, although more would be good.

Love that they give the fitting guide and plan, should be able to make a cardboard template easy enough.

Do you have one of the battereis, or do you know if the base of the battery ends up flush with the top surface of the downtube when its fitted, if thats the case then they claim all you need is 8mm clearance above the battery to slide it in place ?

 

[StuartsProjects]

I was referring to the big rivnut tool in post #5. Eclipse batteries are good if they fit.

Ah, I see.

I had seen the rivnut tool, and did wonder also.

 

[Zlatan]

How are you going to get that massive tool in the corner of the triangle if you can't get a drill in to drill the hole?

It's quite surprising where you can get a tool to fit???!!! Don't need much space with a little application... But I did say in first post I had to use bolt type fitting tool on one of rivnut on cube I did a few months ago. But even then, I would recommend the proper threaded tool than make shift bolt/spacer etc for stainless rivnut. For their cost it's not worth messing with. (MK engineering used to make a cracking little insert tool, was only £5 or something. I, ll see if I can find mine and post pictures.

 

[simon77]

Do you have one of the battereis, or do you know if the base of the battery ends up flush with the top surface of the downtube when its fitted, if thats the case then they claim all you need is 8mm clearance above the battery to slide it in place ?

It just arrived in the post this morning So not fitted it yet.
Looking at it though I'd say add 2 mm for the rubber washer / mount things. So an extra 10mm on top of the 96mm. I just tried unlocking it and I'd say the 18mm and 8mm clearance sounds fair.
When I ordered it I hadn't realised it appears to come with an android app where you can monitor individual cell performance/condition which is a bonus.
That said, it's only been out of the box for a quick look so can't comment on long term use.

Edit - had a bit more of a play. I would say it's an either 18mm or 8mm. In that it you only have 8mm above you will need about 6 cm of "sliding space"; and if you only have 18mm of "sliding space" you will need about 25mm above. That's being really conservative and assuming you don't rotate the battery out and can only move the battery along it's base and perpendicular to it's base. Hard to explain in text!

 

[StuartsProjects]

With my cardboard template, I place the bottom end of the battery against the seat tube.

Then when I move the battery forward 18mm, to free it from the bracket I presume, there is 18mm clearnace form the top of the battery to the top tube.

The plan says the battery needs 8mm clearance to release the battery, so allowing a couple of mm for mounting washers etc, there should be room to get the battery out.

 

[simon77]

With my cardboard template, I place the bottom end of the battery against the seat tube.

Then when I move the battery forward 18mm, to free it from the bracket I presume, there is 18mm clearnace form the top of the battery to the top tube.

The plan says the battery needs 8mm clearance to release the battery, so allowing a couple of mm for mounting washers etc, there should be room to get the battery out.

hmm, I'm not sure that's enough. Eclipse might know better. Or if you are near Twickenham, cycle round and try mine!

 

[simon77]

hmm, I'm not sure that's enough. Eclipse might know better. Or if you are near Twickenham, cycle round and try mine!

 

[StuartsProjects]

hmm, I'm not sure that's enough. Eclipse might know better. Or if you are near Twickenham, cycle round and try mine!

I am in Cardiff, unfortunatly.

Can I ask, assuming the battery is in its bracket washers underneath, flat on the table, how far up, and how far forward do you need to move it to release it from the bracket ?

 

[StuartsProjects]

Based on the measurements on the battery diagram, I added 10mm to the bottom and 18mm to the rear of the battery.

The image is the templete tapes in place, and at this point the battery should be clear of the bracket. Its close.

Might be worth try, unless anyone knows of a smaller, removeable, battery circa 36V/10Ah.

 

[simon77]

Love the cardboard! My frame is a slightly more of a 'traditional' shape - but I'll mount it later / tomorrow to try and replicate the 18mm gaps you have and see how I get on.